Stereo Audio for Television

Stereo sound is very natural to the listener since they already hear things in stereo through two ears. Stereo gives the viewer the ability to localize the direction of the sound and judge the distance of the sound source.

Most people are used to the constant left-right sound and picture orientation. However, some sports events do not lend themselves to this type of coverage. For example, camera coverage of gymnastics, baseball, and athletics tends to be head-on looking at the athlete, plus over-the-shoulder and wide shots. In these situations, stereo sound generally consists of an open, non-specific ambience, with sounds emerging from the left and right sides of the screen and the athlete sounds front and center. Tennis, basketball, and football easily lend themselves to a good left and right sound image.

Figure 9.1 Surround sound speaker placement.

Stereo microphones on handheld cameras have been one of the biggest improvements in stereo sound for television. They deliver close, crisp, definable field of play sport sound, while giving a depth of field and spatial orientation to the pictures.

Basic 5.1 Surround Sound

When mixed correctly, surround sound can provide a sense of envelopment, a feeling of being there. The basic requirement for 5.1 channel mixing/production is a mixing console with six discrete output buses: 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). Surround sound is obtained by the A-1 panning between the five main channels and routing to the LFE channel (see Figure 9.1). This setup offers the greatest flexibility of sound placement in the surround field. The A-1 usually mixes surround sound to the following speakers:

• Announcers’ voices are on the left front, center, and right front speakers.
• Sound effects are usually on the left front and right front.
• Atmosphere/ambience microphones are rout ed to the left rear and right rear speakers.
• Music is usually routed to the front left and right and the rear left and right speakers.
• The LFE track is usually used for rumble from the effects tracks.

The audio assignments to the surround channels as listed above are the most commonly used. However, there are also debates about how to change the various surround sound channels. A-1 Dennis Baxter suggests that the existing channel usage be entirely changed for sports events in surround. He believes that “sports television does not need the LFE channel or the center channel for dialogue—you could hear the commentators just fine in the days of stereo.” His idea is to:

Take these two extra audio channels and implement a pair of speakers above the viewer or design sport sound as a front, middle and rear combination of channels and speakers, essentially three stereo pairs. Just think about the creative possibilities!

He thinks it could be accomplished with metadata and “smart speakers.”

There are many different views on how to record surround sound. Some professionals prefer the use of separate microphones; others choose to use just one surround sound microphone. Jonathan Freed, an audio mixer for NFL and NBA events, has chosen to go with a single surround sound microphone: “I feel that this technique provides the most realistic image in space to achieve the sonic illusion of being in a virtual location in the venue. Plus, it’s easy: it’s one microphone, it has one mounting point, and it’s got all its connectors available. It’s a good timesaver.”

On the other side is Fred Aldous, a Fox Sports audio consultant/senior mixer. He believes that independent microphones allow him more flexibility in manipulating the outputs from independent microphones for levels, spatial positioning, or effects than he would with a single point microphone. Ryan Fitzgibbon, creative director at Holophone, says that: “Our microphones are not intended to replace discrete elements but to add ambience to them. Use the mic to get what the venue sounds like and then mix the individual discrete sound elements on top of that. Bottom line, it comes down to individual taste.”

Audio Levels

Audio levels are generally talked about in terms of decibels (dB). “0” decibels has been established as the standard. However, “0” on a VU meter is a relative scale. It is always referenced to some standard level such as +4 dBm or +8 dBm. The most commonly used is +4 dBm.

There are basically two groups of audio signals—line level and microphone (mic) level. Line level is “0” on the VU meter, which is +4 or +8 dBm. Most audio outputs from machines are line level.

The second type of audio signal is called mic level, and is within the range from –50 dB down to around –60 dB on professional microphones. Most microphones fall into this group. Anything more than –70 dB is generally considered to be noise.

These two different audio levels are not compatible. Mic level cannot be heard on line level and a line level would greatly distort a mic level input.

Microphone Pickup Patterns

There are two primary types of audio pickup patterns.

Microphone Sound-Generating Elements

There are basically two types of microphone sound-converting mechanisms used for sport remotes—dynamic and condenser.

Dynamic: Dynamic microphones are by far the most durable. They can withstand high sound levels without distortion or damage and they are generally the top choice of ENG/EFP production personnel. Dynamic microphones need little or no regular maintenance. However, they are not quite as high quality as the condenser microphone, mentioned below.

Figure 9.2 Omnidirectional microphone pickup pattern.

Figure 9.3 Cardioid and hyper-cardioid microphone pickup pattern.

Condenser: Condenser microphones are very sensitive when it comes to weather conditions or physical abuse. They must be powered by a power supply, an inboard battery pack, or a phantom-powered audio board. The electric condenser microphone uses a polarizing voltage that is impressed into the diaphragm or backplate during manufacture. The charge remains for the life of the microphone. This type of microphone usually has a higher-quality audio sound than the dynamic microphone, even when placed at a greater distance from the audio source.

Condenser microphones have two other design advantages that make them ideal for sports broadcasting—they weigh much less than dynamic elements, and they can be much smaller. These characteristics make them the logical choice for shotgun, lavaliere, and miniature microphones of all types.

Types of Microphones

Audio is like a paintbrush, you have to learn the tools but then have the imagination to hear things in your head and how you want to capture it.

Bob Dixon, former Director of Sound Design, NBC Sports

Shotgun Microphone: The shotgun or line microphone, usually a condenser, is probably the most commonly used microphone on sport remotes due to its ability to pick up quality sound from a distance. It is especially used to pick up sounds from the field of play and to microphone the audience. The shotgun is very sensitive. It must always be carried in a shock mount to avoid picking up extraneous sounds made by the person holding it. This microphone is also very sensitive to wind noises so windscreens must be used when working outdoors (see Figure 9.4).

Figure 9.4 Shotgun microphones are used to capture sound from a distance. The second photo shows the microphone inside a “blimp” that is designed to reduce noise.

Figure 9.5 Handheld microphone.

Handheld Microphone: The handheld microphone, or stick mic, is primarily used by talent reporting from the field of play or conducting an interview. It can also be used in a parabolic dish. Most handhelds are designed to be held 15–30 cm from the mouth. Talent should speak across the microphone, not into it, and hold it at roughly a 45-degree angle to the mouth. Differential handheld microphones require a close proximity, allowing the talent to talk directly into the microphone. This close proximity to the microphone allows the talent to talk over loud background sound (see Figure 9.5).

Headset Microphone: The headset microphone is used by sportscasters who need to have their hands free. Headset microphones ensure the microphone will be the same distance from the announcer’s mouth at all times, allowing more freedom of movement and consistent audio quality. This microphone allows their hands to be free for working with notes (see Figure 9.6).

Lavaliere or “Mini” Microphone: The lavaliere, “lav,” or “mini” microphone is generally used by on-camera talent. It is also often used in a parabolic dish. The lavaliere is clipped onto clothing approximately 15 cm below the chin and is most often used as a wireless microphone. This microphone is popular because it is always at a consistent distance from the talent’s mouth yet is not as bulky as the headset microphone. It is important to conceal the microphone cord so that it is not seen by television viewers. Lavaliere microphones can be as small as about 3 mm (see Figure 9.7).

Figure 9.6 A wide variety of headset microphones exist.

Lavaliere microphones are also used to pick up sounds in places where the microphone should not been seen. For example, it is commonly used on basketball backboards to pick up the sounds of the ball hitting the hoop or the sound of the ball going through the hoop.

Clip Microphones: Clip microphones are used for close-microphone situations where it is imperative to place a hidden, or low-profile, microphone close to the source of the sound. The close proximity of microphones to an athlete gives a very close and personal perspective of the sport and eliminates shotgun microphones from the visible field of play. Examples of how this small microphone has been used include clipping it to a gymnastics apparatus or a net in volleyball (see Figure 9.8).

Figure 9.7 Lavaliere microphones. The second photo shows a lavaliere microphone attached to a basketball backboard to pick up the sound of the ball hitting the board, hoop, and net.
Source: Microphone photo courtesy of Audio-Technica.

Contact Microphones: Contact microphones listen to vibrations, not acoustic sounds. These microphones can be buried in the sand at sports such as beach volleyball and at events in athletics. It gives a completely different impact sound that should be subtly mixed into the program. This microphone’s sound must be layered; it cannot stand alone. The sand microphones are generally mounted on Plexiglass and buried in the pits (see Figure 9.9). Contact microphones can also be screwed into a wooden surface such as a basketball court, attached to gymnastics equipment, or frozen into the ice for speed skating.

Surround Sound Microphone: Inside the larger microphone casing is a microphone array capable of recording up to 7.1 channels of discrete surround sound without additional processing. This one microphone terminates into eight XLR microphone cable-ends (left, right, center, low frequency, left surround, right surround, top, and center rear) (see Figure 9.10).

See p. 110 for some suggestions for using a surround sound microphone from Holophone:

Figure 9.8 Clip microphones can be attached in out-of-sight locations such as this gymnastics horse. They capture the sound without being seen.
Source: Microphone photo courtesy of Audio-Technica.

Figure 9.9 A contact microphone being buried in the sand at a long jump competition. The microphone picks up the vibration of the landing.
Source: Photos by Dennis Baxter and Andrew Wingert.

1. Give the mic the best seat in the house and let it do its work.
2. Use the mic to provide the “base” ambient surround sound for your mix.
3. When mixing surround mic tracks with other audio tracks for broadcast, including for voice-over or sportscaster talent, try to mix the dialogue not only into the center channel, but also place the dialogue slightly in the left and right and to some degree the surround channels for increased spatial realism.
4. For sports broadcasting in most field sporting events, and for fixed installations such as arenas, it is desirable to place the surround mic either near the center of the field, or else near a main camera position off to the one side that will work in conjunction with the main camera angle of the broadcast. Mounting the mic on a side of a field or rink opposite to the main camera angle would seem backwards and unnatural.
5. For track sports, including motor sports or running events with multiple camera angles on corners, hills, or jumps, you can employ multiple surround mic units with an audio switcher from unit to unit. Use this configuration in conjunction with a camera switcher to match the changing perspectives of the cameras.

Figure 9.10 Holophone surround sound microphone.

Figure 9.11 Digital processing microphones can cut out specific frequencies.
Source: Photo by Dennis Baxter.

Digital Processing Microphone: Digital processing microphones use an analog microphone capsule with digital processing of that capsule. The microphone can reject certain frequencies, allowing it to pick up a specific sound, such as the kick of a ball, the punch of a boxing glove, or the landing of the shot put (see Figure 9.11).

Boundary/Pressure Zone Microphone: While the pickup technology is very different, these two microphones are used similarly. This type is especially useful for being a low-profile microphone that has the capability of picking up quality ambient sounds. These microphones can be mounted on a hard surface to increase the pickup distance (se Figure 9.12).

Figure 9.12 Boundary microphone.

Figure 9.13 Commentator’s noise-cancelling ribbon microphone.

Commentator’s Noise-Cancelling Ribbon Microphone/Lip Microphone: Designed by BBC engineers in the mid-1950s, the “lip ribbon mic” is used for reproducing high-quality commentary from noisy surroundings by cancelling out a high degree of background noise. Although this is probably the highest-quality commentary microphone, it must be handheld, unlike the headset microphones that allow the commentator to use both hands for papers. Another disadvantage is that the microphone obscures the commentator’s mouth, which is not great for television (see Figure 9.13).

Specialty Microphones: Just as specialty cameras are designed to cover specific sports situations, specialty microphones are created to fit unique audio events. Existing microphones can be adapted or rebuilt to capture audio that cannot be heard in any other way. Figure 9.14 shows a specialty microphone that was specifically designed by Audio-Technica to capture the sounds of yachting at the Olympics. The wireless and waterproof microphone was mounted on a buoy in the water.

Figure 9.14 Specialty microphone designed specifically to capture the sounds of yachting.

Phantom Power

All types of microphones can be “phantom” powered. Phantom microphones require voltage that is supplied to them through an audio mixer, recorder, or camera. There are two different types—P and T. The P, phantom/ simplex standard, requires a balanced 48 volts. The T, often referred to as A-B powering, is unbalanced 12 volts. These two types of microphones are not interchangeable and will not work if the incorrect voltage is attached. In fact, microphone components may be damaged if interchanged. The T standard was created primarily for television so that a camera head, which had trouble supplying 48 volts, could supply the power to a microphone. Some manufacturers actually put a T or P as part of the microphone model number for easy identification.

Microphone Accessories

Wireless: The wireless could be considered as a type of microphone, however almost all of the microphones we have mentioned can be wireless. Lavaliere microphones are probably the most commonly used wireless microphones because they allow the talent to have unrestricted movement while speaking. The wireless lavaliere is great for capturing an athlete’s words or breathing during a competition or for picking up the calls from a coach or referee. Wireless microphones actually work on radio frequencies (RF) and many are “frequency programmable,” allowing the audio personnel to select the best transmission frequency for a specific location. Some wireless microphones can transmit as far as 305 m. However, it is essential that audio personnel test the various locations where a wireless will be used in order to check for dead spots that either deteriorate or block the audio transmission. It is also occasionally possible to pick up other transmitting devices, such as police radios, or have interference from other wireless microphones. Since these microphones operate on batteries, it is important that new batteries be installed before each production and that crew members have spares available during the production (see Figure 9.15).

Shock Mounts: Shock mounts reduce mechanical noise transferred to a microphone through its mounting hardware or physical contact (see Figure 9.16).

Parabolic Dish: A parabolic dish uses an omnidirectional microphone aimed directly at the focal point of the dish, providing an extremely narrow pickup pattern (see Figure 9.17).

These work well to screen background ambience in a venue, allowing the audio personnel to pick up the sounds generated by the athletes during a competition. Handheld or lavaliere microphones can be used with parabolic dishes. A wireless microphone is especially useful since the dish may need to be moved up and down the field of play. Although the quality of the audio is not always the highest, it works well for background or ambient sounds. It would not be good to use a parabolic dish for commentators. The keys to obtaining good sound with a parabolic dish are:

• Find a position that provides a clear path to the field of play. The microphone must be aimed directly at the field since the dish cannot pick up sound through a crowd of people.
• Stay alert and focused on the action occurring on the field of play.
• Listen closely to the microphone so that it can be finely tuned (aimed at the sound). Sounds will be very clear when the “beam” is in the right place.

Figure 9.15 Wireless microphones.

Figure 9.16 Microphone shock mount.

Figure 9.17 Parabolic dish.

Windscreen: Windscreens protect the microphone sound-generating elements from the wind or air generated by the talent’s mouth. When working outside, windscreens are essen tial for every type of microphone. While windscreens cannot protect the microphone from all wind noises, they can significantly reduce unwanted rumbling sounds. Wind screens take a variety of forms from foam rubber to the shaggy variety known as the windjammer (see Figures 9.4 and 9.18).

Figure 9.18 Microphone furry windscreen attached to camera.

Figure 9.19 Handheld microphones are usually used for interviews at sports venues.

Microphone Placement

My production philosophy is if you see it, you should hear it.

Peteris Saltans, Senior Audio

The key to microphone placement is finding the location that will allow you to capture the specific audio you want. Considerations include analyzing the sport from a sound perspective, the type of microphone, sound sources, whether the microphone can be seen by the camera, and whether sounds are present that you do not want to record. When determining microphone placement, place the microphones as close as possible to the audio source to ensure the highest-quality sound. The farther the distance between the microphone and the audio source, the poorer the sound quality, and the possibility of picking up unwanted sounds is increased. Christopher Lyons, senior audio engineer, Shure Audio, recommends that the lowest number of microphones possible be used: “People sometimes have a tendency to over-mic a shot, using three or four microphones when one or two would be sufficient. Excess mics mean more background noise pickup, greater chance of feedback or tin-can sound, and more levels for the operator to keep track of. If additional mics don’t make things sound better, then they will probably make things sound worse.”

Camera-Mounted Microphones: Camera micro phones, generally shotguns, are attached to the camera so that the viewer will hear exactly what they are seeing from that camera (see Figure 9.18).

Talent Microphones: Talent, meaning anyone who appears on camera, uses specific microphones for different situations:

• In a broadcast booth, commentators usually use headset microphones to keep their hands free for notes and to have the ability to keep the microphone at a consistent distance from their mouth.
• Lavaliere microphones are generally used for interview situations or when the talent is on a set. The lavaliere’s prime advantage is that it is small and unobtrusive.
• Handheld directional microphones are especially popular for interviewing on the field of play. The handheld gives the interviewer the ability to control the interview by directing the microphone at the subject. Handhelds are valuable because they can be placed very close to the mouth when there are loud background noises. They will help pick up what the commentator is saying and diminish background sound (see Figure 9.19).

Figure 9.20 Fixed microphones are placed in select locations at a venue in order to pick up specific sounds.

Fixed Microphones: A variety of fixed microphones are used to capture specific sounds:

• Shotgun microphones may be used when trying to capture specific sounds on the field of play.
• Handheld microphones are generally used to capture ambient sounds. Avoid placing the microphone where it will pick up specific people or the public address system.
• Due to the small size of a lavaliere microphone, it is sometimes used when the micro phone needs to be hidden. For example, if the A-1 wanted to catch the sound of hands on the rings during a gymnastics competition, the lavaliere could actually be mounted on the chain holding the rings (see Figure 9.20).

Soccer Sidekick

Mixing board manufacturer Calrac has introduced a new surround sound audio tool for soccer called Soccer Sidekick. It is an iPad app that is an assistive mixing tool designed to simplify tracking the audio during a soccer game. The iPad’s screen shows a soccer pitch. The A-1 defines the location and direction of each of the microphones and places them on the iPad’s soccer pitch. Once defined, the A-1 can touch the corresponding area of the field of play on the iPad. Soccer Sidekick then calculates the optimal contribution from each microphone to best capture events at those locations and moves the appropriate faders on the desk. The operator can take manual control of the faders at any time, maintaining complete control.

(Photo courtesy of Calrec)

Wireless Microphones: Wireless microphones can be used with umpires or referees, in parabolic dishes, and anywhere else that audio cables would get in the way or be difficult to run (see Figure 9.15).

(Note: See Appendix III for examples of audio microphone placement diagrams)

Gamestime Audio

My goal has been to paint a picture with the sound, not just cover the action. Theater of the mind, just close your eyes and feel the boxer’s pain with each punch. Experience the thundering sound as you hit 200 miles per hour in a Formula 1 car. Good sound accentuates the soundtracks of life.

Dennis Baxter, four-time Emmy Award winning sound designer

The types of microphones being used and microphone placement is determined during the planning phase. Microphones are cabled and placed during the setup phase. Therefore, at production time, the A-1 or senior audio person should be ready to mix the event. Audio inputs come from a variety of sources, which may or may not include:

• multiple talent;
• public address system;
• field-of-play microphones (including camera microphones);
• ambience microphones;
• crowd microphones;
• audio player/recorder;
• player/coach/referee wireless microphone; and
• multiple types of video players.

The A-1 is responsible for mixing all of these audio signals into a clear representation of what is actually occurring at the event (see Figures 9.22 and 9.23).

The A-1 must concentrate on which camera is being called for by the director, as well as know which talent is going to speak. Then, he or she can “pot up” the corresponding microphone in order to provide the audience with the sound from the proper source.

During the production, the A-2 or audio assistant’s responsibilities include hand-holding microphones, making sure that wireless microphones have good batteries, changing batteries, keeping the appropriate microphone flag on the microphone, and troubleshooting any problems with the microphones and cables. Sometimes a microphone or cable may need to be changed during the broadcast.

Figure 9.22 The A-1 is responsible for mixing all of these audio signals into a clear representation of what is actually occurring at the event.

Figure 9.23 The A-1 has a large variety of audio signals coming into the mixer that they must manage.

Communications (Intercom) Systems

While microphone signals flow to the OB van for the on-air program, communication between producers, camera operators, and other television engineers is accomplished through another set of wires that make up the intercom. This television intercom communications system utilizes equipment that functions very similarly to a telephone. The A-1 is responsible for the intercom system for the remote production crew and routes the various channels to the appropriate personnel.

To communicate from production and engineering to field operators, a headset and intercom box is plugged into a cable that runs to the OB van. This cable is plugged into an intercom channel so that operators can talk to the truck.

Intercom systems may comprise many different types of intercoms and subsystems. The three basic systems can be categorized as party-line, matrix and wireless systems, as well as any combination of the three types. This information is adapted from Handbook of Intercom Systems Engineering.

Wired party-line systems involve a number of participants in the same conversation. Everyone can speak to and hear each other in a “public” conversation. This system may be referred to as party-line (PL), two-wire (TW), referring to the two wires required, or a conference, denoting the type of activity taking place in the conversation.

A wired matrix system is an intercom system in which a large number of individuals have the ability to establish private individual conversations from point A to point B at the same time. The matrix system is not limited to simple point-to-point communications. Like telephone systems, they also have other functions and capabilities, including conference, call waiting, and busy signals. This type of system is also referred to as a cross-point intercom, point-to-point system, private line, or some of the various brand names, such as McCurdy, Adam™, Zeus™, and others.

Wireless systems encompass all sorts of systems, from the most basic pair of walkie-talkies, to mobile phones, to dedicated professional intercoms. The most basic feature of wireless intercoms is that they are not tethered by wires. Wireless intercom systems are employed where their limitations—interference, battery life, lack of range, and lack of security—are outweighed by the freedom of being cordless. A wireless intercom can be designed, installed, configured, and operated in PL or matrix configurations, and may be connected to a hard-wired PL or matrix intercom system at some point. They can range from a simple single pair of units talking to one another, to a system in which 24 or more different portable units are dynamically switched between conversations.

There are basically two types of intercom user stations. These include belt packs and master stations.

Belt Pack: This portable single or two-channel intercom headset box is designed to be worn on a user’s belt, but is often fastened to the underside of consoles, taped to a structure near the user, or mounted on a piece of equipment. The intercom headset plugs into the belt pack, as does the connection to the rest of the intercom (see Figure 9.24).

Master Station: The master station allows a director to access multiple channels. This allows different crews to be monitored, cued, or updated. The master station includes both an intercom user station and an intercom system power supply combined in one package.

Cables should be organized so that the intercom signal flows in the direction of the male connector. This is the way the equipment that you must attach to the wire is usually designed. Microphone signals flow toward the truck or camera. Intercom signals flow away from the truck.

Most mobile units/OB vans have from 12 to 24 channels of intercom and an additional 12 interruptible fold-back (IFB) channels that are used to communicate to on-air talent. In most cases, only the producer, director, and possibly the spotters will need to communicate with the on-air talent.

It is not uncommon to have backup transmission equipment actually transmitting the same program on a different microwave link or satellite. That way, if something happens with your primary transmitter, the production still gets to the intended distribution source. Although backup plans may seem like an unnecessary expense, if a problem occurs you will have saved yourself the cost of losing the production.

The producer will determine which crew members need to talk to each other and whether they should use an intercom channel or a two-way radio. Most of the time, the producer will be talking with the director, assistant director, font coordinator, technical director, and tape and RF camera operators. The intercom will be programmed so that the producer can talk to all of them or individually. Also, producers will have an “all call” switch that allows them to talk to everyone on IFB.

The director will primarily want to talk with the camera, graphics, and video recording operators. The technical director will want mainly to listen to the director and talk with camera operators, videotape operators, and the A-1.

Prerecorded Audio

Pregame, post-game, and half-time productions offer a myriad of challenges for audio. There are a number of areas that require quality sound, making it almost impossible to only go with “live” sound. The concept of prerecorded audio can be a bit controversial and is highly debated, even among professional audio designers. Anti-prerecorded audio designers often feel that you are not being truthful about the audio. Pro-precorded audio designers state that sports is entertainment, and movie entertainment always dubs in the audio at a later time. Prerecorded audio is often used to supplement and sometimes completely replace live sound. The following is a list of some of the reasons prerecorded audio was used during the Barcelona Olympic Games Opening Ceremony. At this event, prerecorded audio was used for every aspect of the ceremony—from the roar of airplanes crossing the sky, to opera singers, to the applause of the spectators.

Figure 9.24 Intercom belt pack and an intercom headset.

1. Prerecorded sound allows for near perfect synchronization of the technical aspects of the spectacle, offering the ability to link sound, lights, camera movement, and other enhancements.
2. Prerecorded sound ensures optimal quality for television, allowing for stereophonic sound (stadium spectators only hear monophonic sound), as well as mixed enhancements.
3. Prerecorded sound allows a better experience or sense of proximity to the event for television viewers. For both television and stadium spectators, prerecorded sound also can direct attention to specific events happening in a very large stadium in a way that live sound cannot.
4. Unforeseen weather conditions, such as the rain or the wind, do not affect the prerecording but can affect live music leading to irreparable distortions in a live broadcast.
5. Unforeseen noises, such as friction between the microphone and the actors’ clothes, movements of the announcers in respect to the microphone, or various feedback effects, can be avoided.
6. The use of prerecorded sound can be more comfortable for the performers in the stadium, especially for the opera singers, some of who, in fact, preferred that their music be prerecorded.
7. There were also several microphones strategically placed in the stadium in order to pick up spontaneous sound during the event, in the form of applause, booing, and cheering.