CHAPTER 10
Audio for Video

 

 

The true mark of an audio track’s success—to sound so natural under a given scene that it draws no attention to itself.

—Walter Schoenknecht, Midnight Media Group

Historically, audio has been slighted in the world of television. Most manufacturers and producers have cared more about the image, relegating audio to an inexpensive, poor-sounding little speaker on television sets. However, if you really want to find out how important audio is to a video production, just turn off the audio and try to follow the story. You will soon get lost. Look away from the screen, with the audio up, and you can still follow the story. Audio is as important to television as the video image. Audio gives images a convincing realism. It helps the audience feel involved. As Dennis Baxter, sound designer for the Olympics, has written, “Audio, in partnership with video, delivers a holistic experience with all of the intense emotion and interesting nuances to the viewer.”

10.1 THE ESSENTIAL COMPONENT

The valuable contribution that sound makes to television cannot be underestimated. In a good production, sound is never a casual afterthought. It is an essential part of the production’s appeal.

People often think of television as pictures accompanied by sound. Yet when the best television productions are analyzed, people are usually surprised that most of the time it is the sound that conveys the information and stimulates the audience’s imagination, while the image itself can be a visual accompaniment. Audio has the power to help the audience conjure up mental images that enhance what is being seen.

Sounds are evocative. For example, consider an image of a couple of people leaning against a wall with the open sky as a background. If we hear noises of waves breaking and the shrill cry of birds, we quickly assume that the couple is near the seashore. Add the sound of children at play, and now we are sure that our subjects are near the beach. Replace all those sounds with the noise of a battle, explosions, and passing tanks, and they are immediately transported to a war zone. They might even appear particularly brave and unfazed, as they remain so calm in the middle of this tumult.

In fact, all we really have here is a shot of two people leaning on a wall. The wall itself might have been anywhere—up a mountain, in a desert, or near a replica in a studio. The location and the mood of the occasion have been conjured up by the sound and our imagination.

Successful audio is a blend of two things:

Appropriate techniques. The way the equipment is used to capture the audio.

Appropriate artistic choices. How the sounds are selected and mixed.

Both are largely a matter of technical knowledge combined with experience.

10.2 THE NATURE OF SOUND

The world about us is filled with such an endless variety of sounds that it is difficult to believe each can be resolved into a single complex vibration pattern. When several sources sound together, their separate patterns combine into an even more complicated form. Yet our eardrums, the microphone diaphragm, and the loudspeaker all follow this combined vibration, and, more miraculous still, our brain interprets the result.

The simplest possible sound vibrations make a regular sinusoidal movement, and we hear the pure tones from a tuning fork, a flute, or an audio oscillator. The faster this oscillation, the higher the pitch. Very slow vibrations (subsonic, below about 15 times a second) and extremely fast vibrations (ultrasonic, above about 20,000 times a second) fall outside our audible range. The frequency or rate of these vibrations is measured in hertz.

The stronger the sound’s vibrations (the greater their amplitude), the louder it seems. Slight vibrations are inaudible, whereas extremely loud sounds can become painful to listen to, as they exceed our threshold of feeling.

Few sources emit “pure” sounds. Most are a complex combination of the main note (the fundamental) and multiples of that note (harmonics or overtones). The apparent quality of a sound will depend on the proportions or relative strengths of these harmonics.

Broadly speaking, a note played by a double bass, an oboe, or a bassoon can be judged by its overall quality. If the response of the audio system is not even over the whole audible range (because of filtering or limitations in the equipment), the proportions of the harmonics can change. Then the quality of the reproduced sound may no longer be recognizable as the original instrument.

10.3 ACOUSTICS

You have only to compare sound in an empty room with the difference that occurs when that same room is furnished or filled with people to realize how acoustics alter sound quality. If we understand the basics of acoustics, we can avoid many of the audio problems that might arise during the production (Table 10.1).

Table 10.1 Coping with Acoustics

When Surroundings Are Too “Live,” Reduce Acoustic Reflections

Move the microphone closer to the sound source. Pull curtains if available. Add thick rugs. Add cushions. Use upholstered furniture. Drape blankets on frames or over chairs. Add acoustic panels (Figure 10.2).

When Surroundings Are Too “Dead,” Increase Acoustic Reflections

Move the microphone farther away. Open curtains to increase hard surface space. Remove rugs. Remove cushions. Remove upholstered furniture. Add board or plastic surfaced panels. Add floor panels (wood, fiberboard). Add artificial reverberation.

When a sound wave hits a hard surface (plastic, glass, tile, stone walls, metal), little is absorbed, so the reflected sound is almost as loud as the original. This is referred to as a live surrounding. Where there are a lot of hard surfaces around (as in a bathroom, a large hall, or a church), a place can become extremely reverberant or live. Sound waves rebound from one surface to another so easily that the original and the reflected versions, completely intermixed, are heard. This can cause considerable changes in the overall sound quality and significantly degrade its clarity. When surroundings are reverberant, reflections are often heard seconds after the sound itself has stopped; in extreme cases, these sounds reflect as a repeated echo. Whether reverberations add richness to the original sound or simply confuse it will vary with the design of the space, the position of the sound source, the pitch and quality of the sound, and the position of the microphone (or mic).

When a sound wave hits a soft surface (curtains, couches, rugs), some of its energy is absorbed within the material. Soft surfaces create a dead surrounding.

Higher notes are the most absorbed, so the sound reflected from this sort of surface is not only quieter than the original sound wave, but it lacks the higher frequencies. Its quality is more mellow, less resonant, even dull and muted. Certain soft materials absorb the sound so well that virtually none is reflected (Figures 10.1 and 10.2). If, on the other hand, the sound is made in a place with many soft surfaces, both the original sound and any reflections can be significantly muffled. When outside, in an open area, sound can be very dead. This is due to the air quickly absorbing the sound because there are few reflecting surfaces. Microphones used outside often have to get closer to a subject than normal to pick up sufficient sound, especially if a person is speaking quietly (Figure 10.3).

FIGURE 10.1
The variety of angles of the set walls, the curtains, carpet, furniture, and people help dampen the live sound—but not too much.

10.4 MONO SOUND

In everyday life, each member of the audience is used to listening with the aid of two ears. As listeners compare these two separate sound images of the external world, they build up a three-dimensional impression from which the direction and distance of sound is estimated.

FIGURE 10.2
Acoustic panels were placed on the walls of this audio room to reduce the “liveness” of the room.

FIGURE 10.3
During the shooting of a dramatic program, the boom operator got the microphone as close as possible, while still being off camera, because open-air sound does not usually travel far.

Nonstereo television sound is not as sophisticated as this. It presents a “single-eared” monaural (“mono”) representation of sound in space. The only due to distance is loudness, and direction cannot be conveyed at all. When listening to mono reproduction, we are not able to distinguish between direct and reflected sounds, as we can when listening in stereo. Instead, these sounds become intermixed so that the combined sound is often muddy and less distinct. In mono sound, we become much more aware of the effects of reverberation.

Because the audience cannot easily distinguish direction and distance, the mono microphone needs to be carefully positioned. Audio personnel need to be careful to consider the following:

Too many sound reflections are not picked up.

Louder sounds do not mask a quieter sound (particularly in an orchestra).

Extraneous sounds do not interfere with the ones we want to hear.

10.5 STEREO SOUND

Stereo sound creates an illusion of space and dimension. It enhances clarity Stereo gives the viewer the ability to localize the direction of the sound. This localization gives the audience a sense of depth, a spatial awareness of the visual image and the sound. However, because the speakers in television receivers are close together, the effect can be somewhat limited. Sound quality and realism are enhanced, but our impressions of direction and depth are less obvious.

10.6 SURROUND SOUND

Surround sound can provide a sense of envelopment when mixed correctly. Instead of the one channel for mono or two channels for stereo, 5.1 surround has six discrete (distinct, individual) channels: left front, right front (sometimes called stereo left and right), center, a subwoofer for low-frequency effects (LFE), left rear, and right rear speakers (sometimes called surround left and right). To present the feeling of depth, direction, and realism, audio personnel pan between the five main channels and route effects to the LFE channel (Figure 10.4).

FIGURE 10.4
A home surround system utilizes six speakers.

10.7 MICROPHONE CARE

Although most people regard the video camera with a certain apprehension, there are those who tend to dismiss the microphone (or mic) all too casually. They clip it onto the guest’s jacket with an air of “that’s all we have to do for audio” instead of treating the mic as a delicate tool. The microphone (and how it is used) is really at the heart of television program sound. If the microphone is inferior, if it is damaged, or if it is poorly positioned, the program sound will suffer. No amount of postproduction work with the audio can compensate for doing it right from the beginning. Program sound all begins with the microphone.

It is not important to know how various types of microphones work to use them properly. They all convert sound waves in the air into a fluctuating electrical voltage (the audio signal). It does help, though, to be aware of their different characteristics.

Although most microphones are reasonably robust, they do need careful handling if they are to remain reliable and perform up to specification. If you drop them, knock them, or get liquid on them, you are asking for trouble.

10.8 DIRECTIONAL FEATURES

Microphones do not all behave in the same way. Some are designed to be non-directional (omnidirectional), meaning they can pick up equally well sounds coming from all directions. Others are directional, meaning they can pick up sounds directly in front of them clearly but are comparatively deaf to sounds in all other directions. A further design has a bidirectional or “figure-of-eight” pattern, meaning it can pick up equally well both forward and backward, but it is deaf on either side.

The advantage of an omnidirectional mic (Figure 10.5) is that it can pick up sound equally well over a wide area. It is great for covering a group of people or someone who is moving around. The disadvantage is that it cannot discriminate between the sound you want to hear and unwanted sounds such as reflections from walls, noises from nearby people or equipment, ventilation noise, footsteps, and so on. The more reverberant the surroundings, the worse the problem. The mic must be positioned so that it is closer to the wanted sounds than to the extraneous noises. This mic is great for picking up ambient or natural (NAT) sounds.

When a directional mic (Figure 10.6) is pointed at the desired sound, it will tend to ignore sounds from other directions, providing a much cleaner result. On the other hand, the directional mic needs to be aimed very carefully. It is also important to make sure that the audio source does not move out of the main pickup zone; if it does, the source will be “off mic.” The off-mic sound becomes weaker, and the audience may hear what the mic is pointed at instead of the desired source.

There are several forms of unidirectional pickup patterns. The cardioid (Figure 10.6) or heart-shaped pattern is broad enough for general use but not overselective, whereas the super- or hypercardioid (Figure 10.7) response has also a limited pickup area at its rear to receive reflected sounds.

FIGURE 10.5
The omnidirectional pickup pattern is equally sensitive in all directions, generally rugged, and not too susceptible to impact shock. This mic cannot distinguish between direct and reflected sounds, so it must be placed close to the sound source.(Drawing courtesy of Audio-Technica.)

FIGURE 10.6
The directional (or cardioid) mic pickup pattern. This broad, heart-shaped pickup pattern (roughly 160) is insensitive on its rear side.(Drawing courtesy of Audio-Technica.)

FIGURE 10.7
Use a supercardioid (or highly directional) pickup pattern wherever you want extremely selective pickup, to avoid environmental noises, or for distance sources.(Drawing courtesy of Audio-Technica.)

10.9 POPULAR TYPES OF MICROPHONES

There are two predominant methods for converting sound energy to an electrical equivalent signal: electrodynamic and electrostatic, better known as dynamic and condenser.

Dynamic microphones are the most rugged, provide good quality sound, and are not easily distorted by loud sounds such as nearby drums. These mics need little or no regular maintenance. They can be handheld without causing unwanted “handling noise” and used in all types of microphone mountings. However, they are just as high quality as the condenser microphone.

The condenser microphone produces very high audio quality and is ideal for picking up music. A significant advantage to the condenser is that it can be very small, making it the logical choice for a shotgun, lavalier mic, and other miniature microphones. The condenser mic is generally powered by an inboard battery, phantom-powered audio board, or a special power supply. The electret condenser microphone has a permanent charge applied when it is manufactured, which remains for the life of the microphone and does not need to be externally powered.

Just as you should preplan camera angles for a shoot, you should preplan mic types and positioning. Carefully plan cable runs and connections, and scout every location to determine if it will cause undesirable noise from air conditioners, trains, traffic, or other uncontrollable sounds that will end up being recorded.

—Douglas Spotted Eagle, Grammy Award-Winning Producer

SUPPORTING THE MICROPHONE

10.10 CAMERA MICROPHONES

If the camera is fitted with a microphone, the theory is that when it is aimed at the subject to capture the video, the mic will also pick up quality audio. However, a lot depends on the situation and the type of sound involved. Nothing beats a separate, high-quality microphone placed in exactly the right place. However, single-camera operators, working by themselves and moving around to various shooting positions, may have to use the camera microphone.

The simplest form of camera microphone is a small built-in mic at the front of the camera. These mics are known to pick up sound from all around the camera, including noise from the camera zoom lens and camera operator sounds. With care, though, this basic microphone is useful for general atmospheric background sounds (traffic, crowds) and is almost adequate for close-up voice. However, it should only be used for voice when better options are not available. With most camera mics, trying to pick up a voice more than four to six feet away results in unacceptably high levels of background noise or acoustical reflections.

The most popular type of camera microphone is the shotgun mic, attached to the top of the camera (Figure 10.8). Plugged into the camera’s external mic socket, this mic will give the best quality long-distance pickup from the subject. As always with directional mics, the shotgun mic must be aimed accurately.

At first thought, a camera microphone provides the simplest method of picking up program sound:

The microphone is positioned on the camera, so you do not need a second person to look after the audio.

Wherever the camera points, the microphone will follow.

There are no problems with microphone boom shadows.

However, the camera microphone has a number of drawbacks too:

The microphone is often too far away from the subject for the best sound. Its position is determined by the camera’s shot, not by the optimum place for the microphone.

Unless the microphone zooms with the zoom lens, and some do, the microphone’s distance is the same for all shots. The camera may zoom in to a close-up shot or take a wide-angle shot, but the sound level remains the same.

The camera microphone cannot follow somebody if they turn away from a frontal position, such as to point to a nearby wall map. The sound’s volume and quality will fall off as the subject moves off mic.

FIGURE 10.8
Shotgun mics are the most popular type of camera microphones.

10.11 THE HANDHELD MICROPHONE

The handheld mic (stick mic) is a familiar sight on television, as it is used by interviewers, singers, and commentators (Figure 10.9). It is a simple, convenient method of sound pickup, provided it is used properly. The handheld mic is best held just below shoulder height, pointed slightly toward the person speaking. It should be as unobtrusive as possible.

FIGURE 10.9
The handheld microphone is widely used for interviews, commentaries, and stage work. If the mic has a cardioid directional response, extraneous noise pickup is lower. If the mic is omnidirectional, it may need to be held closer to the subject to reduce atmosphere sounds. The mic is normally held just below shoulder height.

To reduce the low rumbling noises of wind on the microphone and explosive breath-pops when it is held too close to the mouth, attach a foam windshield on the microphone. Note the yellow foam windshield in the interview photo in Figure 10.9. Whenever possible, talk across the microphone rather than directly into it. This will provide the optimal audio quality.

Handheld microphones with cardioid patterns help reduce the amount of extraneous sound overheard, so this type of mic can be used about 1 to 1.5 feet from the person speaking. An omnidirectional handheld mic will normally have to be held much closer, about 9 inches away.

When the talent is walking around with a handheld mic, make sure he or she has plenty of mic cable, or use a wireless handheld. The talent should be able to move around easily without the cable limiting movement. It is important to run the cable out of sight of the camera. Gaffer tape can be used to tape the cable to the floor.

10.12 THE SHOTGUN MICROPHONE

The shotgun microphone (hypercardioid) consists of a slotted tube containing an electret microphone at one end. This microphone is designed to pick up sound within a narrow angle while remaining less sensitive to sounds from other directions. It is great for isolating a subject within a crowd or for excluding nearby noises (Figure 10.10).

FIGURE 10.10
The shotgun microphone is one of the most used mics in television. These microphones are very susceptible to handling noise and must be held or connected to a pole or stand with a shock mount.

When shooting in very “live” (reverberant) surroundings, a shotgun microphone has advantages because it will pick up the subject’s sound successfully while reducing unwanted reflections, although how effectively it does this will depend on the pitch or coloration of the reflected sounds.

The shotgun microphone is adaptable and is regularly used as follows:

A handheld microphone supported by some type of shock mount (see Figure 10.10)

Connected to the end of a boom pole or fishpole (see Figure 10.12)

In the swiveled cradle support of a regular sound boom or perambulator boom (see Figure 10.1)

As a camera microphone, fitted to the top of the camera head (see Figure 10.8)

Most people working in the field fit a shotgun microphone with some type of a windshield (windjammer or wind muffler; see Figure 10.11). The most effective types for suppressing obtrusive wind noises are a furry overcoat with “hairs” or a plastic/fabric tube. An alternative design of wind filter is a tubular plastic sponge (see Figure 10.10). Although much lighter, this may prove inadequate except in the lightest breeze.

FIGURE 10.11
Different types of windshields are used to protect a shotgun mic from wind noise.

10.13 USING THE SHOTGUN MICROPHONE

Selecting the best position for a shotgun microphone takes some preplanning. Audio personnel need a clear idea of how the action is going to develop. They may get this from a briefing beforehand or find out from a camera rehearsal:

Will the shotgun be used for long takes or for brief shots? It is one thing to stand in a fixed position as someone talks directly to the camera and another to have to follow action around as people and cameras move through a sequence.

Will audio personnel have an uninterrupted view of the action?

Is anyone or anything going to get in their way, or are they going to get in anyone else’s way?

Audio personnel should try to position themselves so that the action moves toward them instead of away from them. Whenever the mic boom holder or the talent moves around, it is easy for the talent to pass in and out of the microphone’s main pickup area. If the talent turns away from the microphone, there is usually no way the mic boom holder can compensate or move onto the sound axis.

10.14 THE SHOTGUN AND THE BOOM POLE (FISHPOLE)

The boom pole has become the most popular choice for sound pickup on location and in many smaller studios. This adjustable lightweight aluminum pole is usually about six to nine feet long and carries a microphone at its far end. The sound cable is either designed inside the pole or is taped securely along the pole.

There are many ways to hold a boom pole:

Above the head, with arms fully extended along the pole to balance it (see Figure 10.12).

Set across the shoulders for added stability.

With the end of the pole tucked under one shoulder. The goal is to get the microphone close enough without showing up at the bottom of the camera’s shot (also see Figure 10.3).

FIGURE 10.12
A mic boom (or fishpole) is a regular method of mounting the shotgun microphone, particularly in the field. It allows the operator to stand several feet away from the subject, reaching over any foreground obstacles to place the microphone at an optimum angle. This position can be tiring if it has to be maintained for a long period of time. However, it may be the only solution when people are standing or walking about.
(Photo courtesy of Dennis Baxter.)

10.15 LAVALIER (LAPEL OR CLIP-ON MIC) MICROPHONES

The lavalier microphone, also known as a “lav,” lapel, or clip-on mic, has become a favorite mic in productions where it is unimportant whether the viewer sees a mic attached to someone’s clothing (Figures 10.13 and 10.14). These microphones are compact, unobtrusive, and provide high sound quality. But they must be used judiciously for optimum results. Clip the microphone to outside clothing (such as the tie, lapel, shirt, or blouse), and noises from clothing rubbing will be kept to a minimum. One of the challenges when using a lavalier mic is that the volume and clarity of the sound can change as a wearer turns his or her head left and right, or toward and away from the microphone.

FIGURE 10.13
Lavalier microphones come in different sizes and shapes. Generally, a lavalier mic is clipped to a necktie, lapel, or shirt. Sometimes a “dual redundancy” pair is used whenever a standby mic is desired.
(Photo courtesy of Audio-Technica and Countryman Associates.)

FIGURE 10.14
The talent is using an “earset” microphone that utilizes the lavalier microphone. It is mounted on a tiny mic “boom” and attached to the ear. It is also available in a flesh color and is almost invisible to the viewing audience. In this situation, it was used on ESPN’s X-Games.
(Photo by Dennis Baxter.)

A lavalier mic can only be relied on to effectively pick up the sound of the person wearing it. When two or three people are speaking, each will need to wear his or her own microphone. This does not mean that the mics won’t pick up the sound from others; it just won’t be the same quality and will not be the same level. When working in noisy surroundings, a small foam windshield over the end of the microphone will reduce the rumble of wind noise. As always, it is important to conceal the lavalier mic’s cable beneath a jacket or shirt.

Lavalier microphones can also be used to record subjects other than people. They are used effectively in sports productions (mounted in places like the nets at a soccer field), and they can be used to pick up the sound of some musical instruments. The clip-on mic in Figure 10.15 is actually a type of lavalier mic.

FIGURE 10.15
Lavalier microphones are often used to record musical instruments or any other subject that requires close miking.
(Photos courtesy of Audio-Technica.)

10.16 BOUNDARY OR PZM MICROPHONE

The boundary microphone and pressure zone microphone (PZM) are low-profile mics that can be used to capture audio from talent that is six or more feet away and do not produce the hollow sound of a hanging handheld mic (Figure 10.16). Although the pickup technology is very different, these two mics are used similarly. These microphones are especially good for dramatic productions where microphones should not be seen (they can be adhered to the back of set pieces). They are also good for stage performances of large groups. They can be hung from the ceiling, set on a floor, or adhered to furniture. The pickup distance can be increased by mounting these mics on a hard surface.

FIGURE 10.16
The boundary microphone is a low-profile mic that can pick up accurate sounds from six or more feet away.

10.17 HANGING MICROPHONE

Hanging microphones are especially designed for high-quality sound reinforcement of dramatic productions, orchestras, and choirs. These mics are suspended over the performance area. Their small size is ideal because they will probably be visible to the viewing audience (Figure 10.17).

10.18 SURROUND SOUND MICROPHONE

Surround sound microphones can capture 5.1 to 7.1 channels of discrete (separate) audio with the multidirectional pickup pattern. Using the small microphone shown in Figure 10.18, the audio can be recorded directly onto the camera’s internal media along with the video image. The small microphone has five microphone elements—left front (L), right front (R), center (C), left rear or left surround (LS), right rear or right surround (RS)—and a dedicated low-frequency effects (LFE) (.1) microphone. Some high-end versions provide 7.1 surround sound. Smaller systems, designed specifically for a camcorder, utilize an internal Dolby Pro-Logic II Encoded line-level stereo output for connection directly to the camera on a single 3.5-mm stereo female miniplug jack (Figure 10.18).

FIGURE 10.17
Hanging microphone.
(Photo courtesy of Audio-Technica.)

Some of the nonlinear editing systems, like Final Cut Pro, have a Dolby logic decoder built in, allowing the channels from the stereo input to be split into the five surround channels. This allows a user to record programs in surround sound without the need for a full surround mixing board.

Surround sound microphones must be positioned carefully (Figure 10.19). They should not just be mounted on top of a camera if the camera will be panning and tilting around. Moving the microphone around with the camera can spatially disorient the audience. Generally these microphones are mounted on a separate stand or clamped to something stationary in order to pick up a quality ambient sound.

FIGURE 10.18
This small surround sound microphone includes a Dolby Pro-Logic II encoder with a line-level stereo output designed for camcorders.

FIGURE 10.19
ABC Television’s Extreme Home Makeover uses a professional surround sound microphone, separate from the camera, to capture the audio.
(Photo courtesy of Holophone.)

Suggestions for using a surround sound microphone:

Use the surround mic to provide the “base” ambient surround sound for the audio mix.

For a concert situation with arena-style seating, place the sound mic a little higher than the orchestra, tilting the nose down toward the performers.

In most situations, try to position the surround mic as close to “front row center” as possible rather than near the back of the room.

When shooting sports events, it is best to place the surround mic either near the center of the field or near a main camera position. Always keep in mind the perspective of the television viewer. Mounting the surround mic on a side of a field or rink opposite to the main camera angle would seem backward and unnatural.

For surround recording of acoustic instruments, including drum kits, pianos, and voice at close range, try placing the mic near or above the instrument that is being recorded. For vocal or choirs, position the singers around the mic and monitor in surround to hear the results.

10.19 MICROPHONE STANDS AND MOUNTS

Microphone stands and mics are useful in situations where the director does not mind the microphone possibly appearing in the shot (Figures 10.20 and 10.21). It is especially useful for stage announcements, singing groups, and for miking musical instruments. It does have some disadvantages. If people move around much, they can easily walk out of the mic’s range. Directors have to rely on the talent to get to the right place and keep the right distance from the mic. It is a good idea to give talent taped marks on the floor to guide them. And, of course, there is always the danger that the talent will kick the stand or trip over the cable.

FIGURE 10.20
An audio person adjusts a microphone stand for an on-location interview project.

10.20 WIRELESS MICROPHONE

The most commonly used wireless microphones are the lavalier mic and the handheld mics (Figures 10.22 and 10.23). Both can be purchased with the wireless transmitter built into the mic (or belt pack) and include a matching receiver. The lavalier mic has been popular because it allows the talent to generally have unrestricted movement while on location. They are used in the studio with interview shows, on referees to pick up their calls, and hidden on actors to catch their words.

FIGURE 10.21
There are many types of microphone stands and mounts, from bottom-weighted telescopic stands to small versions with thin, flexible, or curved tubing intended for lavalier or miniature mics.
(Photos by Paul Dupree and Dennis Baxter.)

FIGURE 10.22
Pictured here is a wireless (radio) belt pack transmitter and receiver. A lavalier microphone can be plugged into the transmitter.
(Photo courtesy of Audio-Technica.)

FIGURE 10.23
Any type of microphone can become a wireless microphone if some type of wireless plug-on transmitter is used. This transmitter converts a dynamic or condenser microphone to wireless, transmitting the signal back to a receiver.
(Photo courtesy of Audio-Technica.)

Wireless microphones generally work on radio frequencies (RF) and many are “frequency programmable,” allowing the audio personnel to select the best frequency for a specific location.

There can be a number of challenges when working with wireless microphones:

These mics work off of batteries. Each battery life is roughly four to six hours. In freezing temperatures, the battery life is usually cut in half. New batteries should be placed in the mic before each new session. Do not leave it to chance, assuming that there is enough capacity left from last time.

If two or more wireless microphones are being used in an area, it is advisable to set them to different RF channels to avoid interference.

When working near large metal structures, there can be difficulties with RF dead spots, fading, distortion, or interference. While diversity reception, using multiple antennas, has improved this situation, it is still cause for some concern.

10.21 HIDDEN MICS

When other methods of sound pickup are difficult, a hidden microphone may be the solution to the problem. Mics can be concealed among a bunch of flowers on a table, behind props, or in a piece of furniture, for example.

However, hidden mics do have their limitations. Although the mic can be hidden, the cable must not be visible or the transmitter must be out of site. Sound quality may also be affected by nearby reflecting or absorbing surfaces. Because the microphone covers a fixed localized area, the talent has to be relied on to play to the mic and not speak off mic.

CONTROLLING DYNAMICS

10.22 DYNAMIC RANGE

Everyday sounds can cover a considerable volume range. Fortunately for us, our ears are able to readjust to an astonishing extent to cope with these variations. But audio systems do not have this ability. If audio signals are larger than the system can accept, they will overload it and become badly distorted. If, on the other hand, sounds are too weak, they get lost in general background noise. To reproduce audio clearly, with fidelity, it has to be kept within the system’s limits.

A lot of sounds pose no problems at all. They don’t get particularly soft or loud—that is, they do not have a wide dynamic range. When recording sounds of this type, there is little need to alter the gain (amplification) of the system once it has been set to an appropriate average position.

It can be difficult to capture audio that ranges from a whisper to an ear-shattering blast. Because the blast will exceed the system’s handling capacity, the audio person must compensate in some way. The most obvious thing to do is to turn down the system’s audio gain so that the loud parts never reach its upper limit. But then the quiet passages may be so faint that they are inaudible. Somehow the audio levels need to be controlled.

10.23 AUTOMATIC GAIN CONTROL (AGC) FOR AUDIO

Cameras generally allow the operator to set the audio manually or automatically. To avoid loud sounds overloading the audio system and causing distortion, most audio and video recording equipment include automatic gain control. When the sound signal exceeds a certain level, the auto gain control automatically reduces the audio input.

In a completely automatic gain system, which amplifies all incoming sounds to a specific preset level, it “irons out” sound dynamics by preventing over- or underamplification. Quiet sounds are increased in volume, and loud sounds are held back. There are no adjustments to make, and the camera operator must accept the results.

The problem with completely automatic gain systems is that when there is a pause in the audio, the automatic gain system amplifies the room sound, which does not sound natural. Whenever possible, use the manual gain control.

FIGURE 10.24
VU meters and bar graphs are used to monitor the audio signal.

Some auto gain systems do have manual adjustments. The idea is to ensure that the gain control is set high enough to amplify the quietest passages without overamplifying the loudest sounds. The auto gain control circuitry only limits sound peaks as an occasional safety measure, depending on the gain adjustment.

10.24 MANUAL CONTROL

The other method of controlling the audio level is to continuously monitor the program while watching an audio level meter. The audio person is responsible for readjusting the audio system’s gain (amplification) whenever necessary to obtain a quality audio signal. That does not mean that the dynamics should be ironed out by making all the quiet sections loud and holding back all the loud passages. “Riding the gain” in this way can ruin the sound of the program. Instead, when sounds are going to be weak, anticipate by gradually increasing the gain and, conversely, slowly move the gain back before loud passages. Then the listeners are unaware that changes are being made to accommodate the audio system’s limitations.

How quiet the softest sound is allowed to be will depend on the purpose of the program. If, for example, the recording will be used in noisy surroundings or shown in the open air, it may be best to keep the gain up to prevent the quietest sounds from falling below −15 or 120 dB. If a piano performance is being shot, to be heard indoors, take care not to overcontrol the music’s dynamics, and use the system’s full volume range.

Unlike automatic control circuits, audio personnel are able to anticipate and make artistic judgments, which can make the final audio far superior. The drawback to manual control is that the audio personnel need to be vigilant all the time, ready to make any necessary readjustments. If they are not careful, the resulting audio may be less satisfactory than the auto circuits would have produced.

There are several types of volume indicators, but the most common on video equipment take the form of visual displays using bar graphs or some type of volume unit VU meters.

A bar graph (Figure 10.24) has a strip made up of tiny segments. This varies in length with the audio signal’s strength. Calibrations vary, but it might have a decibel scale from 250 to 110 dB, with an upper working limit of about 12 dB. Simply adjust the audio gain control so that the sound peaks reach this upper mark. Twin bar graphs are used to monitor the left and right channels.

The VU (Figure 10.24) meter is a widely used volume indicator. It has two scales: a “volume unit” scale marked in decibels and another showing the “percentage modulation.” Although accurate for steady tones, the VU meter can give deceptively low readings for brief loud sounds or transients such as percussion.

Maximum signal coincides with 100% modulation /0 dB. Above that, in the red sector, sounds will distort, although occasional peaks are acceptable. The normal range used is 220 to 0 dB, typically peaking between 22 and 0 dB.

In summary, if the camera operator needs the audio system to look after itself because he or she is preoccupied with shooting the scene or is coping with unpredictable sounds, then the automatic gain control has its merits; it will prevent loud sounds from overloading the system. However, if an assistant is available who can monitor the sound as it is being recorded and adjust the gain for optimum results, then this has significant artistic advantages.

10.25 MONITORING THE AUDIO

Monitoring sound for a video program involves the following:

Watching. Check the volume indicator and watch a video monitor to make sure that the microphone does not pop into the shot inadvertently.

Listening. On high-grade earphones or a loudspeaker, listen to check sound quality and balance and to detect any unwanted background noises.

Ideally the audio level can be adjusted during a rehearsal. However, if a performance is going to be recorded without a rehearsal, such as an interview, ask the talent to speak a few lines so that the audio level can be accurately adjusted. It is best if the talent can chat with the host in a normal voice for a few minutes, or he or she can read from a script or book long enough to adjust the level. Do not have the talent count or say “test.” Both can give inaccurate readings because they do not necessarily reflect normal speaking levels.

It is important to monitor the sound to also get an impression of the dynamic range while watching the volume level. If the results are not satisfactory, you may need to ask the talent to speak louder, more quietly, or to reposition the mic.

10.26 THE AUDIO MIXER

An audio mixer is needed whenever there are a number of sound sources to select, blend together, and control (such as a couple of microphones, CD, audio output from a video recording, etc.). The output of this unit is fed to the recorder (Figure 10.25).

On the front panel of the audio mixer are a series of knobs or sliders. Each of these “pots” (potentiometers) or “faders” (Figure 10.26) can adjust its channel’s volume from full audio to fade-out (silence). In some designs, the channel can be switched on or off on cue with a mute button.

FIGURE 10.25
The portable audio mixer is used in the field to mix up to three mics; the overall output is controlled by a master fader. A VU meter provides the volume indicator. Some mixers include a limiter to prevent audio overload.
(Photo courtesy of Shure Incorporated.)

On a large audio mixing panel, there may be group faders (group masters, sub-masters). Each of these group faders controls the combined outputs of several channels, and it may have its own group volume indicator. For instance, one group fader can be used for all the mics on the audience.

Finally, there is a master fader that controls the overall audio strength being sent to line (such as on the recorder). This can be used to fade the complete mix in or out. A master volume indicator shows the combined strength of the mixed audio.

FIGURE 10.26
Faders (potentiometers) on a large audio mixer.

Larger audio mixers include a cue circuit (audition, prehear, prefade), which enables audio personnel to listen privately on earphones or a loudspeaker to the output of any individual channel, even when its pot is faded out. That way, the source, such as a CD, can be set up at exactly the right spot, ready to be started on cue, without this being overheard on air. Mixers are slowly incorporating more and more surround sound capabilities (Figure 10.27).

FIGURE 10.27
A large surround sound audio mixer for television productions.

10.27 USING THE AUDIO MIXER

Is operating an audio mixer a matter of just fading up a microphone or two and controlling the sound levels, or is it a complex process involving edge-of-seat decisions? The answer depends on the type of production. Consider these examples:

A “live” show, which is transmitted or recorded as it happens, involves rapid decisions. There is inevitably a feeling of urgency, tempered with caution. When working on a production that is being taped scene by scene, there is time to set up complicated audio treatments. Anything that goes wrong can usually be corrected and improved.

When a number of sound sources need to be cued in at precisely the right moment, the situation poses different problems than those posed by a less complicated program such as an interview.

Have the incoming sources already been prepared, such as when using prerecorded material, or do the live incoming sources need to be controlled and continually monitored and adjusted?

These are just a few of the issues that decide how complex the audio mix needs to be. Let’s look at typical operations in some detail:

Sound sources should be faded in just before they begin (to the appropriate pot setting), and they should fade out when the audio source is finished.

Source channels should not be left “open” (live) when not in use. Apart from accidentally recording overheard remarks (“Was that all right?”) and other unwanted sounds, the channel may pick up someone who is on another mic.

It is important that the right source is selected and faded up/down at the right moment. Individual or group faders can be used. Here is an example: Imagine a scene for a drama production is being shot. The audience sees the interior of a home, where the radio (actually from a CD player located near the mixer) plays quietly. An actor is talking (on live mic 1) to another person (on live mic 2) who is not shown in the shot. A nearby telephone rings (fade up using a special effects CD of a phone ringing). The actor turns down the radio (we fade down the CD) and picks up the phone (we stop the special effects CD). Continuous background noises of a storm (from another special effects CD) can be heard at a low level throughout the scene. All these fades must be completed on individual channel pots. The different tape and CD machines must be operated by the person at the mixer or by an assistant.

When combining several sound sources, all of them should not be faded up to their full level. They should be blended for a specific overall effect. For example, if a single microphone was used to pick up the sound of a music group, chances are that the one microphone would pick up certain instruments much better than others. Loud ones would dominate and quiet ones would be lost. The overall balance would be poor. Instead, use several microphones, devoted to different parts of the group. Then the volume of the weaker instruments, such as a flute, could be increased, and the volume of the louder ones, such as drums, can be decreased. With care, the result would sound perfectly natural and have a clearer overall balance.

Sometimes the relative volume of a sound will need to be adjusted to create an illusion of distance. If the sound of a telephone ringing is loud, we assume it is nearby; if it is faint, it must be some distance away.

Sounds may need to be deliberately emphasized. For example, you may choose to readjust the pot controlling the crowd noise to make it louder at an exciting moment and give it a more dramatic impact.

The final audio mix needs to fit the mood of the overall production.

10.28 NATURAL SOUND

Most video productions are made up of a series of shots, taken in whatever order is most convenient, and edited together later to form the final program. This approach has both advantages and drawbacks. As far as the program sound is concerned, there are several complications.

First of all, although the various shots in a sequence have been taken at different times, it is important that their quality and volume match when they are edited together. Otherwise there will be sudden jumps whenever the shot changes. If, for instance, a shot is taken of a person walking down a hallway, using a dose mic, and then a side view is shot of the same action, using a more distant mic, the difference in the sound, when cutting from one shot to the other, could be quite noticeable. The overall effect would draw attention to the editing.

When editing together a sequence of images shot at different times, the background sounds may not match. In the time between shooting one shot, repositioning the camera, adjusting the light, and then retaking the shot, the background noises often significantly change. Because the crew is busy, they may not notice that the background sounds are different. Sounds that we became accustomed to while shooting the scene—such as overhead aircraft, farm equipment, hammering, or typing—can have a nasty habit of instantly disappearing and reappearing when the shots are edited together.

When on location, it is a good habit to record a few minutes of ambient sound, background noise, on the recorder. It does not matter what the video is showing at this point; we are only really concerned with the audio. However, it is sometimes helpful to shoot the scene being recorded so that it gives the editor a visual reference as to where it was recorded. It is surprising how often this natural (NAT) sound or wild track comes in handy during audio editing for use as background sounds.

Even when shooting under what seems to be quiet conditions, there is a certain amount of background noise from air conditioners, equipment hum, and so on. A wild track of this natural sound can be used later to cover any periods where there is a break in the soundtrack during editing. Wild tracks also can help during those awkward moments when background sounds in successive shots do not match. They can serve as a bridge to disguise when silent and sound shots are edited together.

10.29 ANTICIPATION

Anticipation comes with experience. When something goes wrong, learn from it and prepare better next time. There are a number of ways to anticipate audio challenges:

Preparation

Check through the script or preplanning paperwork, and then pull together the appropriate equipment so that every audio situation in the production can be covered.

Check prerecorded audio inserts before the show. Make sure that each one is appropriate. Is the duration too long or too short? Is the quality satisfactory? Is the insert material arranged in the order in which it is to be used?

Check all of the equipment to make sure that it is working correctly. Don’t rely on the notion that it was okay yesterday. If additional plug-in equipment is being used, such as a portable audio mixer, have someone fade up each source (microphones or CD) to ensure that each one is working.

Go to each microphone in turn, scratch its housing (which is an easy way to test the microphone), and state its location to make sure that the microphone is working and plugged into the correct input (“this is boom A”).

Have a backup microphone ready in case the main microphone fails. If it is a one-time-only occasion and you are using a lavalier mic, it may be advisable to add a second “dual redundancy” lavalier mic too (see Figure 10.28).

Is the microphone cable long enough to allow the boom pole to move around freely?

Of course, these are all a matter of common sense, but it is surprising how often the obvious and the familiar are overlooked. These are just reminders of what should become a regular routine.

FIGURE 10.28
This lavalier clip is designed to hold two microphones, providing a backup microphone in case one fails.

10.30 ANTICIPATING SOUND EDITING

When shooting a scene, it is important to overcome the challenges of sound editing by anticipating the types of problems that will occur:

Continuity. Try to ensure that the quality and level of successive shots in the same scene match as much as possible.

Natural/atmosphere sounds. Record some general natural sounds (for atmosphere) and typical background sounds (wild track) in case you need them during postproduction.

Questions. When shooting an interview and concentrating on the guest, the questions of the interviewer may not be audible. Make sure the host has his or her own microphone, or go back and have them ask the same questions after the interview so that they are recorded.

10.31 FILTERED SOUND

Significant changes can be made to the quality of sound by introducing an audio filter into the system. It can be adjusted to increase or decrease the chosen part of the audio spectrum and to exaggerate or suppress the higher notes, bass, or middle register, depending on the type of filter system used and how it is adjusted.

The simplest “tone control” progressively reduces higher notes during reproduction. A more flexible type of audio filter is called an equalizer, which can boost or reduce any segment(s) of the audio spectrum by changing the slider pots.

Here are typical ways in which filtering can enhance the subjective effect of the sound:

Cutting low bass can reduce rumble or hum, improve speech clarity, lessen the boomy or hollow sound of some small rooms, and weaken the background noise from ventilation, passing traffic, and so on. Overdone, the result sounds thin and lacks body.

Cutting higher notes can make hiss, whistles, tape noise, sibilant speech, and other high-pitched sound less prominent. However, if you cut them too much, the sound will lack clarity and intelligibility.

If the bass and top are cut, the sound will have a much more open-air quality—a useful cheat when shooting an “exterior” scene in a studio.

By slightly increasing the bass, the impression of size and grandeur of a large interior can be increased.

The clarity and presence of many sounds can be improved by making them appear closer; do this by boosting the middle part of the audio spectrum (such as 2 to 6 kHz).

Filtering can make the quality of sound recorded in different places more similar (such as shots of someone inside and outside a building). It can help you to match the sound quality of different microphones.

10.32 REVERBERATION

As we saw earlier, most of the everyday sounds we hear are a mixture of direct sound from the source itself together with “colored” versions reflected from nearby surfaces. The quality of that reflected sound is affected by the nature of those surfaces. Some surfaces absorb the higher notes (curtains, cushions, carpeting). This reflected sound may even be muffled. Conversely, where surroundings reflect higher notes more readily, these hard reflections will add harshness (edginess) to the final sound.

This is a reminder that the room tone will depend on its size, shape, carpeting, drapes, easy chairs, and similar factors. Where there are no reflections, as in open spaces away from buildings or other hard surfaces, the resulting sound will seem dead. The only way we can simulate dead surroundings within a building is to use carefully positioned sound-absorbing materials. On the other hand, if there is too much reverberation, the result is a confused mixture of sound that reduces its clarity.

In practice, the appeal of many sounds can be enhanced by adding a certain amount of real or simulated reverberation to them. Today, the most commonly used method of adding some “liveness” is to use a reverberation unit that digitally stores the sound and is selectively reread over and over to give the impression of reflected sounds.

10.33 PROGRAM MUSIC

The role of music in television programs is so established that we don’t need to dwell on it here. Musical themes often remain in the memory long after the program itself has faded from the mind.

Music can have various purposes:

Identifying. Music associated with a specific show, person, or country.

Atmospheric. Melodies that are intended to induce a certain mood, such as excitement.

Associative. Music reminiscent of, for example, the American West or the Far East.

Imitative. Music that directly imitates, such as a bird song, or music with a rhythm or melody that copies the subject’s features, such as the jog-trot accompaniment to a horse and wagon.

Environmental. Music heard at a specific place, such as a ballroom.

10.34 SOUND EFFECTS

Sound effects add depth and realism to a video production. They significantly impact the audience’s experience. Interestingly, if a production is shot in a real location yet is missing the everyday sounds that occur there, the audience will perceive that it is a contrived location. However, if the same scene is shot in a well-designed television studio setting but is accompanied by the appropriate sound effects, the audience can easily be convinced that it was shot on location. The barely heard sounds of a dock ticking, wind whistling through trees, bird song, passing traffic, the barking of a distant dog, or whatever other noises are appropriate bring the scene to life.

Sound effects can come from a number of sources:

The original sounds recorded during a scene. For example, a person’s own footsteps accompanying the picture, which may be filtered, reverberation added, and so on.

Reused original sounds. Examples would include the sounds of wind, traffic, or children at play that were recorded during a scene and are copied and mixed with that same scene’s soundtrack to reinforce the overall effect.

Foley. Creating sounds in a studio that can replace the original sounds. For example, introducing sounds of your own footsteps for the original ones; keeping in time with those in the picture.

Sound effects library. Effects from a commercial audio effects library on CD or DVD.

Digital processing or sound sampling. Computer software offers a plethora of options for creating and manipulating sounds. With the use of a keyboard, these effects can be repeated and changed in an endless variety of ways.