Sound Track: The Built-in Mike

Answers to some common questions about the built-in mike.

Depending on how you look at it, your camcorder’s built-in mike is either a great convenience or the ultimate compromise. On the plus side, the built-in mike is always properly plugged into your camcorder, it has no batteries of its own to run out of juice and it doesn’t take up extra room in your camcorder bag. Negatives? The built-in mike doesn’t sound all that great most of the time, you can’t swap it out for a better design and it’s never any closer to your subject than your camcorder is.

In the next few pages, we’ll answer some common questions about built-in microphones. If you’ve got a burning question that you don’t see answered here, mail it to us (or email to editor@videomaker.com)--we’ll address it in a future "Tech Talk" column.

I’m really unhappy with the sound of my camcorder’s built-in mike. Is there any way to modify or replace it for better sound?

Unfortunately, there’s no simple way to improve the sound of a camcorder’s built-in mike by changing the hardware. Most camcorders integrate the microphone into the case itself, making it virtually impossible to access the mike element without completely disassembling the camcorder. Even if you could tear into the camcorder, you still face several problems. First off, what would you replace the existing mike element with? If you had a different mike element to put in, there’s an extremely good chance it wouldn’t fit, or couldn’t be mounted to the chassis, or wouldn’t have the right type of wiring or wouldn’t sound better after all...

I’ve heard that I’m stuck with my camcorder’s built-in mike. How do I get the best possible sound from it?

First off, let’s pinpoint where most built-in mikes fall short. Though it may come as a surprise to many, the main limitation to the quality of a built-in mike’s sound is not the mike itself. It’s quite possible that a $200 condenser mike mounted atop your camcorder would give you little improvement in sound quality over your built-in mike.

How can this be? Simple--the real culprit behind the washed-out sound of a built-in mike is too great a distance between the mike and your subject(s). The cardinal rule of good sound is to get the mike as close as possible to the sound source. In the world of all-in-one camcorders, however, the best distance to capture images is rarely the best distance to record sound. Few videographers set up their shots based on what they’re hearing in their headphones. Instead, we usually get the best visuals we can and leave the mike to fend for itself.

To get the best possible sound from your built-in mike, try favoring your mike instead of your lens. Experiment with getting closer to your subject, shooting things at wider zoom settings. If you don’t need to be 40 feet from your subject, move in. Not only will this give you more crisp, up-close sound, but you’ll enjoy steadier handheld images to boot.

Why does my built-in mike seem to pick up every little gust of wind, and what can I do about it?

Designing an effective wind filter into a mike requires a fair amount of room for foam or other wind-absorbing materials. Few camcorders have the space for such a luxury, so most built-in mikes get wrapped in little more than a thin layer of foam. Any wind above a light puff goes right on through, where it can then manhandle your camcorder’s mike diaphragm.

As an after-the-fact "solution," many camcorders include a wind-filter switch. This filter simply throws away your bass frequencies (where we hear wind noise the most), leaving your audio with a thin, tinny sound. Unless you like your audio to sound like it’s coming through a cheap transistor radio, this is no solution at all.

The best way to avoid wind noise is to avoid wind. Try to shoot as little as possible on really windy days. If you can’t avoid windy conditions, try to position yourself behind the shelter of trees or buildings. If you must shoot in high winds, rotate your camcorder until you find an angle where the wind noise is least severe. For some camcorders, this will be where the wind is blowing across the mike instead of directly into it.

If your built-in mike sits atop the camcorder, you may be able to wrap the mike assembly in a blanket of light, open-cell foam. On all-in-one models, some folks have had good results taping a layer of foam over the mike. Attached with black electrical tape, a small piece of charcoal gray foam may be nearly invisible on your camcorder.

It’s easy to tell if a piece of open-cell foam will work for wind protection without muffling your recordings. First, hold the foam a few inches from your mouth and blow through it. If you can feel breath on the other side, the foam is too porous. Next, put the foam right up to your lips and blow again. If it offers a lot of resistance, the foam may be too dense. Finally, cover one ear with the foam and listen through it. If you can hear a noticeable dulling of sound (your own voice, for example), the foam will have the same effect on your recordings.

My camcorder’s built-in zoom mike sounds really strange as I’m zooming. Why is this?

You can think of most camcorder "zoom" mikes as two mikes in one. One mike is stereo, pointing out to the left and right sides of your camcorder. The other is a directional mono mike, which points straight ahead. As you zoom, the camcorder adjust the balance between these two mikes. Zoom in tight, and the camcorder progressively turns down the stereo mike. Zoom out, and the balance shifts away from the mono mike until all you’re hearing is the stereo mike.

Frankly, this sounds strange because it is strange--there’s no natural precedent for this stereo (two ears) to mono (one ear) transition. Our eyes have grown used to the similarly unnatural visual zoom; our ears are still caught off-guard by an "aural" zoom. For this reason, many folks find the zoom mike to be a gimmick that ransacks the continuity and realism of recorded sound.

To make matters worse, there’s really no such thing as a "zoom" mike. No microphone--not even the best shotgun mike--can approach the selectivity of the camcorder’s zoom lens. For more on the difference between directional mikes, see last month’s feature "The External Mike."

If you can disable your camcorder’s zoom mike, try shooting in the "wide" position only. This will give you spacious stereo sound regardless of your lens’ zoom setting. If you can’t shut off your zoom feature (or prefer not to), try to zoom only between shots. This will improve the look as well as the sound of your videos.

Why does my camcorder’s mike pick up more and more room noise when my subject stops speaking?

This is not so much a problem with your camcorder’s mike as it is with its record electronics. Most camcorders have an auto gain control (AGC) circuit, which tries to put a strong audio signal on tape at all times. When someone is speaking, the circuit adjusts the record level for that sound. When it hears "silence," the circuit keeps increasing its sensitivity until background noises become a dull roar.

If you can set your record levels manually, this is the best solution. Manual record levels disable the AGC, preserving the difference between sound and silence. Unfortunately, there’s no simple solution apart from using manual record level controls, and most consumer camcorders do not have these. As a last resort, you can always run your sound through an audio mixer as you edit, compensating for the action of the AGC circuit with the mixer’s fader.

My camcorder’s built-in mike picks up lots of noises from its own motors and buttons. What can I do to eliminate these sounds?

This problem is closely tied in with the previous question. As your camcorder’s AGC struggles to put something on tape, it often begins picking up zoom- or focus-motor noises, transport noises or the click of fingers on buttons. Apart from disabling the AGC, there are a few tricks you can use to compensate.

For starters, try using manual focus. Even if you’re shooting a stationary subject from a set distance, most autofocus systems continually make fine adjustments to the image. This creates unwanted noise, unnecessary wear on the motors and needless draining of the battery. Likewise, if you can avoid zooming during quiet sections, you’ll get less motor noise on tape. Lastly, try to refrain from pushing buttons on your camcorder until there’s an appreciable amount of sound for the mike to pick up.

Putting your camcorder on a tripod--and not touching it--will also go a long way toward eliminating unwanted noises.