What is a lavalier microphone, and how to get a clean track from one

A lavalier microphone, also called a lav, tie clip or body mic, is a miniature capsule worn on the talent. It sits a hand's width from the mouth, so it stays close and consistent no matter how the actor moves or where the camera is.

Omni or cardioid

Most film lavs are omnidirectional. Because they are so close to the source, they do not need directivity to reject the room, and an omni is far less sensitive to being knocked off axis when the head turns. Cardioid lavs exist mainly for loud stage use, where spill and feedback matter more than natural tone.

Where to place it

• Centre of the chest, roughly 20 cm below the chin, is the default.
• Higher gives more presence and more breath, lower gives more chest and less intelligibility.
• Under a shirt placket, in a tie knot, in hair or on a hat brim, depending on wardrobe.
• Avoid anything that moves against the capsule: collars, scarves, jacket zips, necklaces.

Killing the rustle

Rustle is mechanical, not acoustic, so no plugin fixes it well. Cage the capsule so fabric touches the mount and not the mic, use loops of tape sticky side out, anchor the cable with a strain relief loop, and tape the cable to the body along its whole run. Test by having the actor move the way the scene needs, not by tapping the mic.

Living with a lav in post

A lav is bright, close and dry. A boom is open and matches the room. Most scenes cut best from the boom with the lav underneath for intelligibility, or from the lav when the boom cannot get in. Cut between them at breath points, and roll off below 100 Hz on the lav to remove chest thump.

On a poly WAV, boom and lavs live on separate channels of the same file. Split them into mono stems, audition each, and level them before they hit the timeline.