Exercise 10
Equalizing Audio

In these three exercises, you’ll practice using the Audio EQ tool and the AudioSuite EQ III 7-band effects to reduce hum caused by electrical interference. You’ll also apply Audio EQ Tool preset filters and create your own telephone-style filter.

Media Used: Agent MXZero

Duration: 25 minutes

GOALS

Add and adjust Audio EQ effects

Use Audio EQ with other audio tools and techniques to mix audio

Exercise 10.1: Removing a Hum with the Audio EQ Tool

In this exercise, a clip has a noticeable 60Hz hum. An ungrounded XLR microphone cable often causes 60Hz hums. XLR microphone cables have three conductors, one of which is a grounding wire that’s used to carry away unwanted electromagnetic interference. Electrical power in North America usually operates at a frequency of 60Hz, so laying an extension cable adjacent to an ungrounded microphone cable often introduces a tone to the signal at 60Hz.

You’ll use the Audio EQ tool’s preset to remove the hum.

Note: Electrical power in Europe tends to be at 50Hz, so the hum created by power mains and ungrounded microphone cables is at the 50Hz frequency.

To remove the hum using the EQ filter presets:

1. Open the AGENT MXZERO > 201 > LESSON 10 > LESSON 10 SEQUENCES > PART 1: HUM BUSTING EQ TOOL.

2. Open the AUDIO tool.

3. Play the sequence, paying attention to Turk’s clip on A3.

Turk’s clip starts at 06:51:05, although it’s the only one on A3 so it will be easy to locate. You can hear a humming sound in the background of the clips that resembles a ground fault hum. This particular hum is a simulated 60Hz hum, with partials (harmonics) at 120Hz, 240Hz, and 480Hz.

4. Open the AUDIO EQ tool, and apply the preset NTSC HUM BUSTER filter from the Audio EQ tool’s fast menu.

Caution: Always monitor the audio levels with the Audio tool to ensure that your adjustments do not overdrive the signal.

Use the remaining time in the exercise to increase the presence of the character’s vocals. Try using the Male Voice with Presence preset and notice the parametric curve displayed in the EQ tool’s graphical display. Then remove the preset and try to create a similar curve yourself.

When working on the Turk character (large man, white jacket), you’ll need to place the midpoint of the parametric curve slightly lower than when dealing with the other characters, owing to his naturally deeper voice.

Exercise 10.2: Removing a Hum with the AudioSuite Tool

Now you’re going to remove the hum again, this time using the 7-Band EQ 3 and the “search and destroy” technique, not the Audio EQ tool and its preset Hum Buster filter.

To remove a hum using the AudioSuite tool:

1. Open AGENT MXZERO > 201 > LESSON 10 > LESSON 10 SEQUENCES > PART 2: HUM BUSTING AUDIOSUITE.

2. Solo A3 to isolate the clip.

3. Mark an IN and OUT to isolate a few seconds of the clip.

4. Select TOOLS > AUDIOSUITE.

5. Select the 7-BAND EQ 3 plug-in, and click the socket to open the plug-in interface.

6. Set the LF BAND TYPE to PEAK.

7. Set the LF Q CONTROL to 10.

A narrow Q is ideal because 60Hz hum does not affect surrounding frequencies. Always change as few frequencies as possible to preserve the original integrity of the sound.

8. Set the LF GAIN CONTROL to + 18DB.

Remember, exaggerating a sound is a good way to precisely locate its frequency or frequencies. Then you can easily eliminate the sound. You’ll use the low-frequency (LF) band to isolate and eliminate the fundamental frequency of the hum.

9. Press the PREVIEW button to loop-play the section.

10. While the section is playing, choose a frequency using the LF control. Start at approximately 200Hz.

11. While still loop-playing, drag the EQ control a little farther down the frequency range, and then wait for the system to catch up so you can play the clip at the new frequency. Repeat until the hum is very pronounced. (This should occur at around 60Hz.) 60Hz is the frequency you want to adjust.

12. To eliminate the sound, set the LF GAIN to –18dB or lower. Now adjust the Q control and determine the best setting.

13. Click the BYPASS toggle button to compare the altered version with the original audio. (You can also add an ADD EDIT within the audio clip, adjust one side, and compare to the unaltered side.)

To truly eliminate 60Hz hum, you’ll need to remove the first few harmonics of 60Hz too. Use the LMF, MF, and HMF bands of the 7-band EQ 3 to eliminate overtones at 120Hz, 240Hz, and 480Hz. Once you’ve finished, you can save the effect to combat 60Hz hum in future projects.

Exercise 10.3: EQ for Creative Storytelling

In the previous exercises, you performed EQ adjustments for technical corrections. But EQ isn’t just about fixing poorly recorded audio. You can also use it for creative storytelling, because sound can also communicate information about the space in which someone is located.

Sound can reverb in a grand hall, like a church, or echo like in a canyon. Sound can also be tinny and thin, like when it’s coming through the tiny speaker of a phone or earpiece.

In this final exercise of the EQ lesson, you’ll use pre-built Audio EQ tool filters to affect sound so that it sounds like it’s coming from a phone. You’ll then remove the pre-built filter and create the same effect on your own.

1. Open AGENT MXZERO > 201 > LESSON 10 > LESSON 10 SEQUENCES > PART 3: TELEPHONE.

2. Locate the two clips containing a blue marker.

The two clips with the blue markers, located at the end of A2, contain the voice of the agent’s assistant back at headquarters. She’s monitoring the agent’s move and communicates to him through an earpiece. You’ll make the sound resemble an earpiece by applying an Audio EQ Filter preset.

3. Apply the AUDIO EQ TOOL > FAST MENU > TELEPHONE A preset to the audio clip at 01:07:26:19.

4. Play back the audio and then replace the filter with the TELEPHONE B preset.

Compare the two telephone effects, paying as much attention to how they sound as to how they look in the graphical display at the bottom of the Audio EQ tool. It’s now time to create your own, using that graphical display for your inspiration.

5. Remove the Audio EQ filter preset, which restores the Audio EQ tool’s sliders. Use the sliders to create a similar EQ filter by trying to recreate the shape of the curve from the preset TELEPHONE filters.

You’ve now learned to create Audio EQ filters for individual clips in your timeline. In the next lesson, you’ll learn to create more sophisticated high-pass, low-pass, and parametric audio EQ filters that affect the entire audio track and don’t require rendering.