Improving the Clarity of Sound
Even under the best recording circumstances, occasionally your audio needs tweaking. Maybe you picked up some background noise you’d like to reduce, perhaps the room you recorded in had an unpleasant resonance, or more commonly, the audio is just a bit thin, or muffled. Equalization, usually called EQ for short, allows you to accentuate or attenuate specific parts of a sound, which can often improve the clarity of the sound, or reduce some unwanted characteristic of the original recording.
Equalization can get very complex, but sometimes a few simple tweaks can make large improvements. There are many optional EQ plug-ins that can be used in most Digital Audio Workstations, but sometimes the simplest ones can do the job.
The EQ plug-in that comes as part of the Hindenburg editing program looks very simple, even limited, but has hidden complexity, making it a very useful tool for improving your audio. Many of these same techniques can be used with any EQ plug-in, although the specific ways of adjusting settings will differ.
The way Hindenburg employs EQ is to apply it to a track, rather than processing individual clips. So all clips on a track will be affected by the EQ you add, by clicking the “effects” button (next to the Mute and Solo buttons, at the left of each track), then choosing EQ in the grid that pops-up.
Because the EQ (and other effects) are applied to all clips in that track, you need to be careful about organizing your session, so that only clips that require the same processing are placed on the same track. That’s generally a good organizing principle in any case: for instance, creating a separate track for each person speaking, perhaps even a different track for the same speaker if they were recorded in a different environment.
Common problems you’re likely to encounter are boomy rumbles from machinery, traffic, wind, or handling noise on your microphone. Those are problems in the low-frequencies, which can often be mitigated by reducing specific frequencies in the lower part of the audio spectrum. One of the most effective tools for reducing low-frequency problems is a low-cut filter, sometimes called a “high-pass” filter because it allows the higher frequencies to pass, while stopping the low frequencies.
The Hindenburg EQ always puts a low-cut filter on by default, it’s indicated by the blue line in the EQ display that slopes down on the left. That filter can fairly effectively reduce rumbles, but you may need to adjust the specific frequency where it kicks in: you can click on the vertical part of the blue line and drag it to the left or right, to make the reduction start at higher or lower frequencies as needed. Set it too low and it won’t do much, too high and you’ll sound thin and tinny like you’re on the telephone.
You can turn off the low-cut filter by clicking the little blue box on the left side of the EQ display.
Recently, while doing some nature recording, I encountered really nice cricket sounds, but there was a distant low-frequency rumble from nearby machinery, perhaps a generator. By using a low-cut filter, and sweeping the position of the curve, I was able to reduce the distracting noise, while keeping most of the character of the sound I wanted.
The low-cut filter can also be very helpful in fixing P-Pops: see the Transom article about Plosives for specific techniques.
Low and High Shelving EQ
There’s also a low “shelving” EQ, which is pretty easy to picture: it raises, or lowers, everything below a certain frequency equally. Turning up the low can warm stuff up, turning it down can clear your sound up if it’s dull and boomy.
On the other end, there’s a high shelving EQ: turning that up raises the high frequencies, which can add “air” and brighten the sound. Turning it down can reduce shrillness and hiss (but also can reduce intelligibility of voices, so be careful to not turn that down too far!). Like with all the adjustments in Hindenburg, it initially appears that you can’t adjust the frequency with the knobs on the screen, you’re stuck with the frequencies assigned by default, but in fact you can adjust the shape and position of the EQ curves by clicking and dragging on the blue line in the EQ display.
Hindenburg’s “Mid” EQ uses a bell-shaped curve that’s called a “Parametric” EQ, which can be used to make broad, or very specific, adjustments. That kind of EQ curve is best for zeroing in on a particular frequency that’s causing trouble, like an S with too much whistle, or a ringing room resonance.
A good way to start with that EQ is to turn the mid control UP, then play the audio and click on the resulting bump in the blue line. Drag that bell-shaped lump to the left and right, until it amplifies the problematic frequency, making it sound extra-bad. Then drag the curve down, below the zero line, to cut the frequency that’s bugging you. For instance, if you had to record in a room that accentuated certain frequencies of the voice, you could use a parametric EQ to reduce the ringy, resonant tone of the room.
A Little Goes a Long Way
There’s no absolute rule, but a good place to start is to make cuts, rather than boosts, to problematic frequencies. But EQ is weird: boosting one frequency range has the same effect as cutting other frequencies, and vice-versa — cutting the low-end can make the high-end sound brighter. So, listen as you make adjustments, because adding or cutting one frequency can impact the audio in ways you don’t expect.
In most cases, gentle cuts or boosts, of only a few dB, will sound best: save the dramatic curve shapes for addressing specific serious problems. A whistle-y S sound, or simple excess sibilance, that sizzle-y S sound that certain microphones may exaggerate, can be addressed with EQ, and in that case, you may want to be very specific about the frequency and make a fairly dramatic cut.
In true Hindy fashion, the midrange parametric EQ looks overly simple, and limited, but there’s actually some hidden power under the hood: if you click on the curve, and then hold the shift key as you drag up and down, it will change the width of the curve, adjusting what is called the “Q” value. Dragging up will increase the Q, which makes the curve narrower and more precise. Dragging down will decrease the Q, making a more gradual curve.
A Rule and Variations
As a rule of thumb: wide curves (low Q), and small boosts or cuts will sound more natural. But sometimes a dramatic, narrow curve is needed, especially a narrow cut, called a “notch” to knock back a very specific problem frequency. And after you’ve made your EQ adjustments, be sure to play the audio and turn the EQ on and off (blue button on right side of plug-in) while it’s playing, just to make sure it’s actually improving things!
Some third-party EQ plug-ins extend additional control by offering more simultaneous bands to adjust, and allowing you to change the shape of most of the bands to parametric, shelving, or high or low pass. The basic Hindy EQ, between the low cut, the two shelves and one parametric, is like a 4-band EQ, it just has some of the bands fixed in their most common positions and shapes.
You can stack up EQs, using more than one EQ plug-in on a channel. That way you can apply multiple bands of parametric EQ that can work in concert with each other.
If you’re using additional processing, the order of the plug-ins can make a difference. If you’re using compression on a track, it’s usually better to place the EQ before (above) the compression in the processing chain. That way, any problematic frequencies you may be adjusting won’t trigger the compressor in extreme ways.
Finding the right EQ settings requires some experimenting, and careful listening, but there are some common places to start. If a recording sounds dull and boomy, try reducing frequencies around 100-200 Hz with a Low Shelf, or a wide parametric EQ. If your audio seems shrill and screechy, try reducing around 1000 Hz with a parametric EQ.
If a speaker’s S sounds are overly present, creating a sharp, piercing sound every time an S is pronounced, you may be able to mitigate that with a narrow-shaped curve with a parametric EQ. The proper frequency to cut varies widely among different speakers, ranging from around 3 kHz up to 7 kHz, depending on how the speaker pronounces the S sound. Try sweeping the EQ around by clicking on the blue line and dragging to the left and right, as shown above, and you’ll probably find a spot where it sounds better to cut a few dB with a fairly narrow curve. A specialized processor called a “de-esser” combines an EQ and a compressor and can do an even better job, but sometimes a simple EQ can make significant improvements on its own.
The Voice Profiler
When working with a voice, Hindenburg has a unique feature called the “Voice Profiler” that can automatically make EQ and compression settings. It won’t work for every voice in every setting, but it’s always worth a try, to see if that algorithm can improve the sound of your voice recording. Hindenburg Pro allows the user to make custom profiles for specific voices, but even the generic profile included in the basic version of the software is often helpful. Make sure to only have one voice on the track, then apply the profiler by clicking the small triangle next to the effects button (at the left of the track), and choose “Apply Profile.” Hindenburg will analyze the audio on the track, and apply a custom EQ. Like with the regular EQ plug-in, the blue line indicates what frequencies are being boosted or cut, and like with the EQ, you can click and drag on the blue line to make additional tweaks if you desire. The profiler is not going to improve every voice recording, but if you don’t happen to like what it does, you can just turn it off! Even if you don’t end up using the Voice Profiler, sometimes it can give you helpful hints about where to boost or cut with the standard EQ plug-in.
Always About the Ear
The regular Hindenburg EQ sounds good and is pretty easy to use once you get used to it. The one major downside is that you can’t save custom configurations, and another is that you can’t cut and paste settings. But it’s usually not too hard to re-create an EQ that you like. So, do some experimenting. In the end, it’s all about listening carefully.