Manual Audio Setting

[Richard Crowley]

Setting recording levels means staying in the “Goldilocks Zone”. In other words, “not too hot and not too cold”. If your levels are too high (aka. “too hot”) then you run the very real and significant risk of clipping the signal at Full Scale. This an especially bad thing in digital recording.

At the other end, setting levels TOO LOW results in a poor signal-to-noise ratio (SNR). All equipment has noise floor levels somewhere. The noise floor is much lower in good (read: expensive) equipment, and higher in lesser equipment.

So setting recording levels from any source is a matter of keeping the signal in the comfortable zone between the noise floor and the full-scale ceiling which will chop the tops off your waveform.

Many lower-end consumer camcorders use “auto-level” which cannot be turned off, so you are stuck with it. But more sophisticated equipment allows the user to manually set the levels.

Manual level control is both a blessing and a curse. It is a blessing in that you CAN adjust the record level in a way suitable to what/how you are recording. OTOH, it is a curse because it REQUIRES you to make an informed judgement on where to set the recording level.

When recording music, it is NEVER appropriate to use auto-level control (ALC). ALC will suck the dynamic range out of almost ANY kind of music. OTOH, for many non-critical talking head or other speech recording, I have been known to use ALC which is switchable as an option on most higher-end cameras.

This is generic advice which applies to your specific situation, but also to most all kinds of audio recording. Of course you know that there are other factors involved with getting good sound beyond simply setting the record levels. Selecting a microphone suitable for the situation, and getting/keeping the microphone at the optimal place are also critical components.

And of course, you ALWAYS monitor your audio while shooting. Either with enclosed headphones (blocking ambient noise, etc.), or with ear-buds. Recording sound without listening to it is exactly like framing and focusing video without looking at the viewfinder.

[John Fishback]

To build on Ricard’s excellent suggestions, you should also listen to playback as there are times where your input audio will sound ok, but it’s in fact being recorded with distortion. Playback is the final test. Some recorders will allow you to monitor sound both at the input and “after” recording – also referred to as return from the recorder. Then, you simply periodically listen to return to assure yourself your recording is solid.

John

MacPro 8-core 2.8GHz 8 GB RAM OS 10.5.8 QT7.6.4 Kona 3 Dual Cinema 23 ATI Radeon HD 3870, 24″ TV-Logic Monitor, ATTO ExpressSAS R380 RAID Adapter, PDE enclosure with 8-drive 6TB RAID 5
FCS 3 (FCP 7.0.1, Motion 4.0.1, Comp 3.5.1, DVDSP 4.2.2, Color 1.5.1)

Pro Tools HD w SYNC IO, Yamaha DM1000, Millennia Media HV-3C, Neumann U87, Schoeps Mk41 mics, Genelec Monitors, PrimaLT ISDN