Headroom and recording level

[steve]

The important thing about headroom is that the peak level never reaches 0 dB.

The suggested peak level of -6 dB (6 dB headroom) is usually sufficient to ensure that the peak level never reaches 0 dB, though it depends what you are recording.

Live music recordings can be problematic, especially with amateur performers, who frequently get much louder once they get going than they do during the sound check. In such cases it can be wise to allow more headroom.

When recording things like records and tapes, the peak level is usually fairly predictable, so it's easier to guestimate the recording levels required to ensure that the level never reaches 0 dB.

The number of tracks is not relevant to setting recording levels. If there's more than one track, you may need to reduce the "track gain" so as to prevent the mix from overloading. The track gain may be adjusted either with the Track Gain slider (https://manual.audacityteam.org/man/aud ... .html#gain) or with the "Mixer Board" (https://manual.audacityteam.org/man/mixer_board.html)

[Jebbers]

I select Show Clipping and do some premixing along the way to see how all the tracks peak when mixed. Is there some reliable math? I understand that 10dB + 10 dB = 13 dB, an addition of 3 dB. Is that correct? And how would the math be for 3 tracks of 10 dB? 16 dB?

[steve]

I select Show Clipping and do some premixing along the way to see how all the tracks peak when mixed. Is there some reliable math?

Except for special cases where the tracks being mixed are related to each other, there is no way to accurately calculate what the peak level of the mix of multiple tracks will be.

An example to illustrate the problem:

1. Generate a tone
2. Duplicate the track
3. Select both tracks and "Mix and Render".
   Note that the mix track is about 6.02 dB higher than the original track
4. Undo the Mix and Render step
5. Select only the second track
6. Apply the "Invert" effect
7. Select both tracks and "Mix and Render".
   Note that the mix is silent.