Audio Level for Recording on Zoom H6 or equivalent
I'm relatively new to Creative Cow, but have spent several hours on internet searches and don't have a satisfactory (or direct) answer to a simple question I have. Perhaps I simply don't understand the available explanations and so I would appreciate someone with the patience to explain this to me.
I've read that there are general guidelines for the dB levels when recording audio. These rules of thumb differ for different recording settings (film, broadcast, dialogue etc) but generally fall somewhere in the -20 to -6 dB range. The main reason for this is to avoid clipping (which is when audio goes above 0 dB and gets distorted).
I am struggling to understand the rationale for a lower bound for the audio. Intuitively to me, the ideal would be to record at as soft a level as possible to eliminate background noise maximally, and then adjust the audio to a pleasantly audible level in post. Why then should we be aiming for something in the ball park of -20 dB? Is it because volumes below that are not audible?
I've just come off a shoot today and tried recording at -40 dB and -10 dB respectively on a Zoom H6 (different scenes, to be fair), and found that comparing the two in post, once they'd been adjusted to sound the same in terms of volume, that the recording at -40 dB was clearer (less noise). Even if it took more adjustment to arrive at a suitable audible level (it was soft when first imported).
I should mention that at the -40 dB recording, it is still possible to hear the playback reasonably clearly when the recorder's playback volume is at 100.
I'm struggling to make sense of this. Is it that:
1. Not all meters on all recorders are calibrated the same, and so -40 dB for me may be -8 dB for another recorder?
2. The logic behind 'record as soft as possible to minimise noise' is mistaken?
3. Should you be basing your judgement of a good take (volume wise) on whether it sounds right through the headphones, or a mixture of headphones and meter, or purely meter?
Thank you for your help.
Note first that there is a big difference between where we RECORD things vs. where we end up MIXING them.
Boiled down to its essence:
Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.
afaik, the recording level is usually bounded by two things, noise floor and dynamic range.
Noise floor is always there, its just at a lower volume so you don't normally hear it.
If the native noise floor of a recorder is -80db and the mic noise floor is -60, then your final noise floor is actually the poorest thing in the audio chain; in this case, the mic at -60db.
When do you start hearing hiss then? Some mics need phantom power and a lot of it to get above the noise floor. Other plugin
power mics need a strong signal to get above the noise floor. All of this is very relative. That is why you can't record something far away and simply turn up the gain.
The other extreme is distortion or voltage levels outside the parameters of either the mic or the recorder. In the digital
world, its a hard limit. analog can push a little past 0db.
So, the best way to answer your other question is that 'normally' the human voice has a certain dynamic range when it whispers, talk normally, and yells. -23db RMS is a good place to start because it lets a person talk both softly and loud without having to compress/limit or clip the audio which is probably what happened to your -10 recording). An added bonus is that the normal talking will usually automatically top out around -12/-10db making post a cince as youtube is -16LUFS and theatres are -23LUFS, all your audio will already be close to the target and be the right volume when you sit in the chair.
There's some sound devices that can analog limit though. So, you may be wondering, "why don't I just record everything at -1db and let my sound devices soft limit for me?" The answer is, beyond a certain ratio like 4:1, voices will sound unnatural. I don't go beyond 4:1 sfx and 2:1 dialogue personally but your mileage may vary. People's ears get tired when dynamic range is too large in a 2 hour movie. Perhaps you've noticed this in some independant films.