There are, typically, three ways to acquire dialogue sound in film production: boom microphones, lavalieres and plants. Boom mics traditionally cover most of the dialogue on a movie set, followed by wireless lavalieres, mounted on each speaking actor, usually in or near the chest (though, depending on circumstances, the Sound Department can, and should, be very creative in lav placement: hairline, glasses, under the brim of a hat… you name it: it’s probably been done.)

Plants are used less frequently, typically in problematic or confined locations, when the boom operator(s) can’t reach the actors. Boom mics and lavs are used indistinctly for this purpose, depending on conditions, space and so on.

Without getting too much into the characteristics of different types of mic, those used on a boom pole (variously called “shotguns” or “boom mics”) can more faithfully capture a broader range of sounds than lavalieres. And the goal of a good sound mixer is to make the best recording possible - Harry Caul, the protagonist of the 1974 film “The Conversation,” played by Gene Hackman, said it best:

    “I don't care what they're talking about. All I want is a nice fat recording.”

(By the way, if you haven’t seen this Francis Ford Coppola film, I recommend it.) Anyway, the point is, our job is to provide the Post Department with a nice, fat wave form. And, typically, a good boom mic, aimed at the speaker, will do a better job than a pin-sized lav tucked under layers of clothing.

There’s another difference between booms and lavs: perspective. Just as you have perspective in images, you have it in sound - it’s just a bit less obvious to us, because we’re so used to think in images.

When the camera shoots a close-up, the boom operator can get the boom mic very close to the actor, whose voice will thus be very present. He or she can whisper, and the recording will sound as near as if we were standing next to the actor.

If, on the other hand, the camera is farther away and is shooting the actor head-to-toe, especially if there’s ample headroom, the boom op can only get the mic a couple of feet away. There will be more air between the actor’s mouth and the mic and, therefore, the sound will be more “airy,” more distant. It’s only natural: you wouldn’t expect someone standing ten feet away to sound as if they were whispering in your ear, right?

So, the characteristics of the sound captured by the boom mic will, by definition, change depending on how far it is from the source: just like with the camera lens, there will be more presence, more details, as we get closer to the subject.

Lavs, on the other hand, always sound the same: VERY present, all the time. Of course, it is possible for the Re-recording Mixer to lower their level, or apply some EQ to make them duller. But these are repairs done in Post, not ideal solutions - it just doesn’t sound the same.

Unfortunately, with the ubiquity of “Reality” TV where, for logistical and other reasons, lavs are the mic of choice, a whole generation of TV viewers has grown accustomed to hearing every dialogue IN YOUR FACE, regardless of the size of the shot. The subtle layers of sound that match what the lens is showing us are squashed.

It’s as if every shot were a close-up. No self-respecting cinematographer would be caught dead shooting a whole project with only close-ups. We wouldn’t expect the Sound Mixer to accept the same thing, now, would we?

Can you tell the difference between a boom and a lav?