Sound Reasoning: Equally Important: The Equalizer

No matter how good you think your video looks, it’s only as good as the audio track that accompanies it. Case in point–say you’ve shot some awesome video at your favorite outdoor concert, and it’s time to begin the editing process. You set up your source deck to review the footage, and find you’ve got plenty of material for a great package. Then you realize something is missing–sound. You turn up the volume on your monitor to find that your audio sounds more like a concert performed by ants than by the Grateful Dead. You thought your camcorder’s built-in microphone would do justice to the music coming from a stage just 30 yards away. You were wrong.

In order to compensate for your thin, weak soundtrack, you turn to one of the best tools in your audio toolbox–the equalizer. The equalizer, or EQ, can pinpoint a range of audible frequencies and adjust the level of sounds that fall within that range. With an EQ, you can minimize noise recorded in the field, boost the weak audio recorded from a camcorder mike and add impressive clarity to a poorly-recorded soundtrack. An EQ will even allow you to create some simple audio effects.

Keep in mind, though, that an equalizer can never fully compensate for a poor recording. But if you set it up carefully, an EQ can go a long way toward restoring an otherwise hopeless soundtrack.

The Equalizer is Your Friend
Remember the rock concert recording? The limited bass response of your camcorder mike kept it from catching the fullness and power of the concert. What it did record was plenty of thin-sounding music and screaming fans. At different times during the concert, mid-to-high range frequencies overwhelmed the lower frequencies of the acoustic and bass guitars.

In order to bring down the screams and crowd noise, you could use the EQ to minimize (or cut) the mid- to high-range frequencies that overpower the soundtrack. Be careful, though–you still want to retain that “live” concert feeling. If you cut too much in the mid and high ranges, you’ll lose the clarity and crispness of the music.

In addition to reducing the upper midrange frequencies, you could boost the bass-level frequencies slightly. This will restore some of the fullness to the music soundtrack. Even though the changes are subtle, your final video package will sound that much more realistic.

When boosting or reducing high and low frequencies, use discretion. Say you want to add clarity to your audio program by increasing the treble, but you don’t want to increase tape hiss. Boosting treble in moderation is the only solution, especially if you’re working with an audio track contaminated with tape hiss.

Boosting high frequencies on your audio program early in the editing process can actually counteract tape hiss and other noise. First, use the equalizer to boost the higher frequencies as you edit from your master tape. Making your audio brighter than normal increases high frequencies before noise has a chance to set in. When making your dub from your master after editing, reduce the high frequencies by the same amount you boosted them when you started. This makes your audio sound normal again, wiping out a considerable amount of noise and tape hiss in the process. This technique, which requires a little experimentation, is especially effective if you’re editing with the somewhat noise-prone VHS-family linear audio track.

Simply adjusting an equalizer’s bass frequency knob can accentuate or reduce the effects of wind noise and mechanical vibration on audio tracks. You can apply the same procedure to clean up audio that has low frequency build-up. This type of build-up, called the proximity effect, occurs when a directional handheld mike sits too close to a speaker’s mouth. This can make him or her sound too deep and unclear. Reducing the bass will remove the unclear and boomy audio. Too much bass cutting, however, will
leave the audio sounding weak and empty.

Highs and Lows
Within the world of audio, there are several species of equalizer to choose from. Some EQs allow control over just the lower bass and upper treble regions. Other units separate the audible spectrum into as many as 30 different ranges or bands. You’ll find some EQs on audio mixers that control the level of up to four frequency bands. More advanced EQs enable you to accurately control the frequency, width and level of each band.

The method for targeting and reducing high- or low- frequency noise depends on the type of equalizer you’re using. The more frequency bands an EQ offers, the easier it is to pinpoint and compensate for the specific offending sounds.

A fixed-frequency equalizer (often bearing knobs instead of sliders) offers a predetermined number of frequency bands to choose from. You can boost or cut the level of sounds at these frequencies, but you can’t control how wide a range of sounds you affect with each knob. You’ll find this type of equalizer on many audio mixing consoles. They commonly provide adjustment in three frequency bands: low, mid and high.

Simpler versions of the knob equalizer allow for frequency selection only at the lower and higher ranges. These EQs consist of only a treble and bass knob, similar to the tone controls on your car stereo. For example, the treble knob will raise or lower frequencies above an assigned point, normally around 10kHz. The bass control knob adjusts frequencies below a certain frequency, usually 100Hz. Control over the midrange requires a third knob, which usually boosts or cuts a relatively broad range of frequencies around 1kHz.

The graphic equalizer offers a series of set frequency bands. These bands are equally spaced according to musical intervals, usually in octaves. (An octave represents an even doubling of frequency.) For example, an “octave band” graphic equalizer may have 10 equalization controls spaced at octave intervals: 20Hz, 40Hz, 80Hz, 160Hz, 320Hz, 640Hz 1.25kHz, 2.5kHz, 5kHz, and 10kHz. The actual equalization controls for the various bands are vertical sliders arranged side by side. The position of the sliders gives you a “graphic” representation of the tonal correction being applied. Increasing the high and low bands, for example, gives the graphic EQ an inverted bell shape.

Because the graphic equalizer can have between 3 and 30 bands, it offers great control over an audio signal. By dividing the audio spectrum into 10 bands, the graphic equalizer has control over much narrower frequencies than would a normal 3-band “knob-style” EQ. A 30 band–or “1/3-octave”–EQ has control over even narrower bandwidths. This type of EQ is great for reducing noise in one band without affecting audio in another.

Most graphic EQs are stand-alone units and are available from a variety of audio electronics manufactures. DOD of Sandy, Utah offers the 830 Series II, a stereo 15-band graphic EQ ($250). For the same price, Alesis (Los Angeles, California) makes the M-EQ 230, a stereo unit with independent 30-band graphic EQs for the left and right channels.

Parametric EQs give you the most extensive sound control possible, because the center frequency of each band is continuously adjustable. This allows you to pinpoint a specific sound or range of sounds with great accuracy. A parametric also offers you control over the bandwidth, which affects how wide a range of frequencies you’re adjusting.

Parametric EQs can adjust a much narrower band of frequencies than graphic equalizers. Parametric EQs offer the best of both worlds–you can make broad tonal changes like the simplest bass/treble knob equalizers, or select a very tight band of frequencies and change its level.

Due to their flexibility and performance, parametric EQs have become the standard compliment to most modern recording and audio production consoles. Furman, of Greenbrae California makes the PQ-4 4-band parametric EQ ($380). Rane, of Mukilteo, Washington offers a 5-band parametric EQ with
studio-quality specs. Called the PE-17, it retails for $499.

Set Up
Now that you’ve decided which EQ will suit your needs, you’re ready to add an external equalizer to your editing system. Most external EQs have 1/4-inch phone or RCA connectors. If you’re not using a mixer, place the EQ between your source and recorder. This will give you control over the audio signal as it travels directly from your source, through the EQ, and out to the recorder.

If you do have a mixer, where you place your EQ in the system will depend upon your needs. In order to equalize a single sound source without affecting the others, you’ll have to place your EQ between the audio signal source and the mixer. If you want to equalize all of your sound sources, place your EQ between the mixer and record deck.

Tricks of the Trade
In addition to fixing problems, an EQ can also create simple sound effects that add to your soundtrack’s realism. Some character voices can sound either too bold or too weak; try reducing higher frequencies in order to add fullness to a whining or raspy-sounding voice. Reducing high frequencies (or boosting lower ones) will also make your tough characters sound more believable and threatening. Likewise, boosting treble and midrange around 1kHz or 2kHz makes a character sound annoying and “in your face.” Cutting high frequencies mutes machinery and traffic noise, simulating sound coming from within buildings or traveling from a distance.

During close-ups or chase scenes, you might want to create a sense of nervousness or high tension. Try boosting the treble or upper mid-range frequencies while slightly lowering bass frequencies. By doing so, your characters will sound like they’re closer to the viewer.

Increasing bass-level frequencies is the key to emphasizing size and power. Instead of sounding like a toy airplane, your 747 jumbo jet will sound massive and robust with adequate bass boost. Sound quality determines the age and personality of voices as well. Treble boost emphasizes younger, immature or nervous voice patterns. Increasing bass frequencies simulates a deeper, older or more trustworthy voice.

EQ Rules
Lastly, here are a few suggestions for effectively applying EQ to your soundtracks. When trying to achieve a certain aural effect, remember to cut before you boost. If you reduce the undesirable portions of your audio signal you will achieve the same effect as boosting those elements you do want. The advantage is, you’ll do it with less distortion of your signal.

In the beginning, apply only the minimum amount of correction and listen to the results. Any EQ can add noise or distortion to your signal if you overuse it. Moving adjacent bands on a graphic EQ in opposite directions will often result in distortion. Use headphones to monitor the effects of your EQ closely. If you first listen to your recorded audio through a good stereo system with a graphic equalizer, experiment with EQ settings before you begin editing. Often, this will save you time in the actual editing process.

Above all, never hesitate to experiment with an equalizer. Try using different settings to locate that “just right” sound. Whether you’re using your EQ for tonal correction or to create special sound effects, experimentation is often the key to a good-sounding audio track.

The Videomaker Editors are dedicated to bringing you the information you need to produce and share better video.

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