Lesson 4 of 7 · about 14 minutes
Sound on Location
You'll be able to
- Pick the right microphone for an interview, a walk-and-talk or a crowd scene
- Place a mic at a distance that keeps the voice clean
- Protect a recording from wind and handling noise
- Record room tone and sync a separate audio recorder in the edit
Viewers forgive soft pictures. They do not forgive bad sound. A slightly grainy interview with a clear voice gets watched to the end, and a gorgeous 4K shot with a voice lost in fan hum gets scrolled past in three seconds. So spend your first $25 on a microphone, not a lens.
This lesson is about getting sound right at the location. Cleaning it up afterward (noise reduction, EQ, loudness) belongs to the Audio Production module and the AV craft chapter Making a voice sound like a voice. Every one of those fixes works better on a good recording, and none of them rescues a bad one.
Distance is everything
The single rule: get the mic close to the mouth. Sound from a source drops about 6 dB each time you double the distance. Double from one foot to two feet and the voice gets noticeably quieter, but the room's hum, the fridge, the traffic and the echo off the walls stay just as loud. So the voice-to-noise ratio gets worse with every step back.
That is why the phone's built-in mic sounds fine in a selfie video (phone 18 inches from your mouth) and awful in an interview shot from across a room (phone eight feet away). The mic did not change. The distance did. The SoundStudio theory page has more on why in its section on noise.
Which mic
| Mic | Best for | Watch out for |
|---|---|---|
| Phone's built-in | Selfie-style pieces to camera at arm's length. Scratch audio for syncing. | Useless past about three feet. Picks up your hands on the case. |
| Wired lav ($15 to $30) | Sit-down interviews. The default choice. | Cable runs to the phone, so subject cannot move far. Clothing rustle. |
| Wireless lav kit ($40 to $150) | Interviews, walk-and-talks, standing in front of a building. | Batteries. Occasional dropouts. Check the receiver is actually recording. |
| Shotgun on a boom pole | Multiple speakers taking turns, scenes where a lav would show, events. | Needs a second person to hold it. Still needs to be within two or three feet, pointed at the mouth. |
| Shotgun mounted on the phone | Better than the built-in for run-and-gun B-roll and short street questions. | Mounted on the camera means it is as far away as the camera. Not a fix for distance. |
For most civic video work, one wireless lav kit with two transmitters covers almost everything: interviews, two-person conversations, and you talking to camera.
Placing a lav
- Clip it to the center of the chest, about a hand's width below the chin. Shirt placket, tie, or the edge of a jacket lapel.
- If the person will turn their head toward you (the interviewer) on one side, clip it slightly to that side.
- Keep it away from necklaces, ID lanyards, scarves and anything that rubs. Rustle is the lav's main enemy.
- Make a small loop in the cable just below the clip and tape it down. The loop absorbs tugs so they do not knock the mic.
- Hiding it under clothing is a skill; start with it showing. Nobody in a news piece minds a visible lav.
Levels
Record a test sentence and play it back with headphones. Every time. Not on the phone speaker, which hides hum and rustle. Speech peaks should land around a third to a half of the meter on most apps, well clear of the top. Too low is fixable later with some added noise; too high clips, and clipping is permanent. The SoundStudio theory sections on decibels and clipping cover the numbers.
Have the speaker talk at the energy they will use in the answer. People always say "testing, testing" quietly and then laugh loudly in the answer.
Wind
Wind physically pushes the mic's diaphragm and overloads it, creating low rumbles and pops that EQ cannot fully remove. Outdoors:
- Put a furry windscreen (a "dead cat") on the mic. Lav kits usually include little furry covers; use them.
- Turn the subject so their body shields the mic from the wind.
- Move behind a building, a truck, a hedge.
- A high-pass or low-cut filter, if your recorder has one, trims some rumble. It helps; it does not replace the windscreen.
Room tone
At the end of every interview, say "Room tone, thirty seconds, everybody hold still," and record the silence. Mic in the same place, same settings.
Every room has a hum: HVAC, a refrigerator, distant traffic. When you cut out an "um" or a cough, that hum disappears for a moment and the cut becomes audible. A piece of room tone laid under the gap fills it. Room tone is also what noise reduction tools learn from. It is the cheapest insurance in video, and the step everyone forgets.
Separate recorder and the sync clap
Many lav kits record into a separate box, or you record audio on a second phone with a voice memo app near the subject. That frees you from a cable and often sounds better. The cost is that picture and sound live in two files, and you have to line them up.
The clap does it:
- Start the camera. Start the recorder.
- Hold your hands in frame, in front of the subject's mic, and clap once, sharply.
- Let the camera keep its own sound running. That scratch audio is your guide.
In the edit, put the video (with its scratch audio) on one track and the good audio on another. Find the clap: a tall spike on both waveforms. Slide the good audio until the spikes line up, check the video frame where the hands meet, then mute or delete the scratch audio. Many editors also sync by matching waveforms automatically; the clap makes that reliable.
Two gotchas. First, record both at 48 kHz if you can choose; that is the video standard, and YouTube lists 48 kHz in its recommended upload settings. Second, on long takes (20 minutes and up), cheap recorders and phones can drift a fraction of a second apart. If the end of a long interview slips out of sync, clap again at the end, or start a new take every 15 minutes or so.
Example: a two-person interview, one phone, one wireless kit
Cordell Ames of the Tarrow County road committee and a farmer whose lane floods each spring. One transmitter on each, receiver plugged into the phone, both on separate channels if the kit allows. Phone on a tripod in 4K for a two-shot, so each person can be cropped into a single later. Headphones on the reporter. Clap at the top. Room tone at the end, with the window AC unit left running because it ran during the interview too.
Try it
- Record the same paragraph three ways: phone across the room (eight feet), phone at arm's length, and a lav or wired earbuds' mic clipped to your chest.
- Record 30 seconds of room tone after each.
- Open them in SoundStudio and look at the waveform: how far above the room tone does the voice sit in each?
- Bonus: record video on one phone and audio on another, with a clap. Sync them on a timeline in AVPrep3 by lining up the spikes.
Checklist
- Mic within about a foot of the mouth (lav: a hand below the chin)
- Headphones on, test sentence played back
- Peaks well below the top of the meter
- Windscreen on outdoors
- Jewelry and lanyards away from the lav
- Clap at the start if recording separately
- Room tone recorded at every location
- Spare batteries for the wireless kit
Check yourself
1. For a sit-down interview with one person and a phone, which cheap mic usually gives the cleanest voice?
A lav sits a few inches from the mouth, so the voice is loud compared to the room. Distance is the enemy, and the lav beats it.
2. You move a microphone from one foot away to two feet away from a speaker. Roughly what happens to the direct voice level?
Doubling the distance from a source drops its level about 6 dB. The room's noise and echo do not drop with it, so the recording sounds roomier and noisier.
3. What is room tone?
Every room has its own hum. When you cut out an 'um', you need that hum to fill the gap or the audio drops to dead silence and the cut is obvious.
4. Why clap once on camera at the start of a take when using a separate audio recorder?
The clap shows as a spike on both waveforms and a visible moment on video. Line up the spikes and picture and sound are in sync.
5. Outdoors on a breezy day, what is the first fix for wind noise?
Wind rumble overloads the mic itself. A furry cover and blocking the wind with the subject's body stop it before it is recorded.
6. When does a shotgun mic make more sense than a lav?
A shotgun on a boom pole, pointed down from just out of frame, can catch whoever talks. It still has to be close; a shotgun is not a long-range mic.
Terms in this lesson
- Lavalier (lav)
- A tiny clip-on microphone worn on the chest, wired or wireless.
- Shotgun mic
- A long, directional microphone that picks up mostly what it points at and rejects some sound from the sides.
- Room tone
- A recording of a location's background sound with nobody talking, used to fill gaps in the edit.
- Sync clap
- A single sharp clap at the start of a take, used to line up separately recorded sound and picture.
- Dead cat
- Slang for a furry windscreen that slips over a microphone.
- Scratch audio
- The camera's own sound, used only as a guide for syncing, not in the final mix.