Exercise 11
Working with Real-Time AudioSuite Effects

The sequence in this exercise contains a lot of audio problems, from hums to muffled voices, to hisses and rumbles. It has the making of a perfect audio mixing storm, and your goal is to make it ready for primetime.

You’ll fix many of the audio problems using the RTAS EQIII 7-Band effect. You’ll also practice the audio mixdown workflow, which allows you to manage the 16 voices available within Avid Media Composer.

Media Used: Agent MXZero

Duration: 30 minutes

GOALS

Use RTAS filters effectively

Improve the tonal balance of an actor’s voice

Create a low-pass EQ filter to remove hiss

Create a high-pass EQ filter to remove rumble

Mixdown the tracks into a new mono track

Apply a Normalize RTAS effect to a mixed down track

Exercise 11.1: Removing Interference and Restoring Vocal Presence

In this exercise, you’ll fix a problem with Agent MXZero’s voice: It’s muffled! There’s also some interference. All it takes is one RTAS and your skills to fix all the problematic clips.

1. Open AGENT MXZERO > 201 > LESSON 11 > LESSON 11 SEQUENCES > PART 1: RTAS EQ.

2. Listen to the sequence.

The audio for the sequence is entirely on track A1. This is typical for dialogue scenes supplied by offline editors. RTAS effects are applied on a track-by-track basis, and must be applied to the entire track, so it’s important to separate the audio of each performer onto separate tracks.

3. Create two new mono tracks: A2 and A3.

4. Use the LIFT/OVERWRITE SEGMENT tool (red arrow) while holding CMD/CTRL+SHIFT to move the audio clips to the following tracks:

A1: Agent MXZero

A2: Mysterion

A3: Turk

5. Solo A1 - AGENT MXZERO and play the sequence.

Agent MXZero’s audio has interference at 4200Hz, possibly caused by cheap circuitry inside the microphone preamps used during recording, or possibly some sort of wireless interference, such as microwave ovens, neon signs, and so on. To eliminate the problem, you first have to locate the exact frequency that is causing the problem, and then attenuate that frequency with a very sharp (narrow) Q.

6. Apply a RTAS EQIII 7-BAND EQ EFFECT to TRACK A1, INSERT A.

Three ways to apply RTAS effects include: right-clicking an insert and using the contextual menu; clicking on an insert and adding the effect from the RTAS window that opens; or dragging an effect from the Effect palette to the track.

7. Open the EQIII 7-BAND EQ effect.

To locate the frequency of the interference, do the following:

8. Choose one band on the EQ, such as MF.

9. Set the Q as narrow as possible, and boost its frequency by +12DB.

10. Slowly sweep the frequency across the spectrum from the lowest to the highest point.

The problem frequency(ies) will jump out of the speakers when the boost crosses it. When the problem is at its loudest and clearest, you’ve located its fundamental frequency, which can now be attenuated.

11. Attenuate the problem frequency once it has been identified.

12. (Optional) If some of the tone remains, the Q can be widened a touch. Make small, refined adjustments to the Q so as not to remove any of the non-problem frequencies.

You can repeat Steps 9–10 if there are overtones remaining, such as in removing a 60Hz hum. You can use the other bands in the EQIII 7-Band EQ effect, or you can apply a new EQIII 1-Band or 7-Band effect to one of the remaining inserts, b, c, d, e or f.

Now the interference is gone, but the sound isn’t quite right—there’s a lack of clarity and it sounds muffled. Although your first thought might be to begin by brightening the high frequencies, it might be better to start by attenuating the low frequencies. A low-cut (high-pass) filter would work, but will also remove the richness from the voice, leaving it thin.

1. Within the EQ III 7-BAND effect, create a low shelf at about 120Hz and attenuate until the low parts of the voice sound even again—between 6 and 8dB.

2. Now that you have removed all the excess and unwanted frequencies, you can boost some of the lacking ones. Create a high-shelf filter to boost the high frequencies from about 5kHz by approximately +5dB.

You have now performed a multi-band EQ correction to fix multiple problems. Thanks to real-time AudioSuite, the adjustment is applied to all clips on track A1, and no rendering is required.

In the next exercise, you continue working with this sequence by moving your attention to track A2.

Exercise 11.2: The Royal Rumblesssssssssss

Your sequence continues to be plagued by problems on tracks A2 and A3. In this exercise, the audio on A2 is suffering from a problem of the extremities: hiss in the high-end and rumble in the low-end. These extra sounds inject extra frequencies into the soundscape and detract from the clarity and intelligibility of the speech. Your mission, should you choose to accept it (and hopefully you will), is to eliminate the hiss and rumble.

You’ll begin with the hiss:

1. Continue with the sequence from Exercise 11.1: AGENT MXZERO > 201 > LESSON 11 > LESSON 11 SEQUENCES > PART 1: RTAS EQ.

2. Solo A2, which contains Mysterion’s audio, and play the sequence.

Mysterion’s audio has a consistent hiss in the high frequency range. You’ll eliminate it by using a low-pass (high-cut) EQ filter, which allows low frequencies to pass and eliminates the high frequencies. (Remember: In a high-cut filter, the low frequencies are allowed to stay, but the high frequencies don’t make the cut. Out they go.)

3. Apply a RTAS EQIII 7-BAND EQ effect to TRACK A2, INSERT A.

You’re now ready to apply the low-pass (high-cut) filter. The EQ III 7-Band effect does not enable the low-pass filter nor the high-pass filter when the effect is applied. You must enable those by clicking the IN button. The IN button is shown as part of the previous lesson in Figure 10.14.

4. Enable the LOW-PASS FILTER (LPF) by clicking its IN button, as shown in Figure 10.14 of the previous lesson.

A low-pass filter removes the high frequencies above a certain frequency that you specify using the LPF FREQ dial in the EQ III 7-Band EQ effect. But high- and low-pass filters don’t usually harshly cut all frequencies above that level. That would sound odd for any frequencies that move above and below the cutoff point.

Instead, the high- and low-pass filters apply attenuation to their affected frequencies according to a slope: The frequencies closest to the cutoff are attenuated less than those farther away. The value of Q is used to specify the slope of the cutoff curve. When Q is used with the high- and low-pass filters, its value isn’t just octaves, it’s decibels per octave, such as 6dB/Oct or 12db/Oct.

Setting Q to 12dB/Oct will create a steeper curve than a 6dB/Oct. A steeper curve means the reduction happens quicker, so fewer frequencies remain above the cutoff value. Turning the LPF Q dial fully clockwise will create a very sharp dropoff.

5. Adjust the LPF FREQ and Q values to attain maximum hiss removal while retaining the most of the original high signals from Mysterion’s dialogue.

The hiss has been reduced, and Mysterion is now easier to hear, but there’s still a rumble in the background. When audio is recorded outside of a sound booth, background sounds from fans and air conditioners or wind are often picked up. Your brain filters them out, but the microphone does not. You need to filter them from Mysterion’s dialogue.

6. Use the same technique from Steps 4 and 5, but this time, work with the HIGH-PASS FILTER, HPF, which cuts the low frequencies.

Exercise 11.3: Creating a Mixdown

In this exercise, you’ll continue with the previous exercise and use a mixdown to reduce the voice-count requirement for the sequence.

1. Using the techniques from the previous exercise, improve the audio for the other characters by applying EQ effects to their tracks.

2. Follow the techniques in the section entitled “Understanding RTAS Mixdown Workflows” to mixdown the tracks into a new mono track.

3. After mixing down your clips, apply a NORMALIZE RTAS effect to the mixed down track.

This is also a good opportunity to explore some of the other RTAS effects beyond EQ.

Next, perform a common audio finishing task—limiting. The purpose of a limiter is to reduce the dynamic range, allowing you to maintain a strong audio signal throughout the program without exceeding broadcast specifications.

There are several limiters in the RTAS Dynamics category. Try using the Compressor/Limiter Dyn 3 after mixing down all of your audio tracks to a stereo track.