You can use Effect > Amplify but this will bring up the surface noise. It would have been better if the person recording the podcast had recorded it higher so that it reached fairly close to top and bottom of the waveform.
If Iâm following, I think the reason for this is that MP3 is a lossy âpsycho-acousticalâ encoding (it selects the audio to retain on the basis of it being the most perceptible). So (in Audacity, anyway, but less so in some other software), the actual peak amplitude of the exported MP3 may exceed what it is in the waveform after Amplify.
If thatâs the reasoning, this should be a negligible problem at higher MP3 export bit rates, but could be a problem at Audacityâs default 128 kbps bit rate.
The main reason Iâd call it the âparanoid levelâ or something similar⌠Picking up a âreal-worldâ analogy Iâll compare it to cooking. When I make soup (my cooking specialty) I usually put less salt than what I should. The reason for this is that adding more salt later, if necessary, is much easier than removing the salt in excessâŚ
So I wonder: is there some minimum level thatâs acceptable? Obviously, on the back end you want to get as close to 0Db as you can without distorting, but if you do have a track thatâs too quiet and Amplifying means bringing in noise, what would be the minimum to amplify to?
Not that I think thereâs one standard out there, since itâs likely dependent on the content of the track, butâŚ
If you are recording, it is reasonable to aim to peak at -6 dB. Digital audio has a wide dynamic range between the noise level and the maximum signal level. Amplifying from -6 dB to 0 dB should not bring up noise noticeably, but it will avoid the risk of clipping above 0 dB, which means in most cases that the clipped audio will be damaged.
If you already have a recording at low amplitude, the signal to noise (SNR) ratio is lower, so amplifying it will make the noise louder as well as the signal. [However, as long as you work in Audacityâs default 32-bit quality, amplifying wonât make the SNR worse].
Only you can judge where the noise subjectively becomes too loud when you amplify, but you can try Effect > Noise Removal to attenuate noise (at the possible risk of introducing artifacts into the audio). If you are encoding to MP3, noise removal artifacts could become somewhat worse because MP3 is a lossy encoding.
Iâve shot for that (-6Db peak) in my last couple of recordings, and then used normalize to get up to around 0Db, and - indeed - I donât hear an increase in noise. Iâve still got lots of monkeying around with noise reduction to do, but thatâs for the tip on peak volume; seems to work well!
Just be aware that unlike the Amplify effect which works on the stereo pair as a pair - the Normalize effect works on each stereo channel independently. Useful if your setup is not balanced properly - but if it is, then you may end up changing/damaging the balance/stereo image.