At the moment I process voice recordings by the same person who tends to every so often have a huge surge in tonality/volume resulting in peaks that are usually about 3-4 times higher than his normal speech. Until now I have been fixing it up manually by locating those peaks visually, selecting and attenuating those by about -5db. I find this process very inefficient and I hope that someone who’s knowledgeable in nyquist could help me write a plugin/script to do this process automatically. I looked at a lot of the existing plugins, but none do what I need.
I’ve attached a snapshot of a sample, which demonstrates those peaks.
Have you had a look at dynamic compressors? There’s one built-in (effects menu → compressor) in audacity. Chris compressor is also quite popular, you can get it from here: http://pdf23ds.net/software/dynamic-compressor/
There are a lot of threads on the forum about dynamic compression.
You also have the leveller effect (effects menu → leveller)
The peaks are from the voice only (not background noises)
The recording machine is just an mp3 player [cowon D2 with line-in microphone], sometimes it goes through a mixer, but there is no mechanism to do anything of a kind in it. other times it goes directly from mic to recorder.
So you would like a .wav sample? how many seconds?
Thank you, I’ve tried the suggested plugins, but they don’t work to the same degree of what I’ve been doing manually.
May be I can rephrase my request: I would like to raise the volume of the whole track several times but those peaks prevent me from doing that via normalize - if I amplify the whole track I get clipping, so I need to go and manually attenuate those peaks that are usually 3-5 times of higher volume than the rest of the track. and doing this manually is very slow and inefficient - trying to find a script that will do that for me. I’d define the job as find the peaks (let’s say 4 times higher than the average) and attenuate those to the average volume.
I’m not sure what you mean “scripted”
What’s wrong with just applying the effect from the Effects menu?
or are you wanting to “batch process” multiple files?
Based on your screen shot you appear to be using a Mac. You should have a pile of AU effects in the Effect menu. If not, go to Audacity > Preferences, the Effects section and under “Enable effects” check “Audio Units”, OK the dialog then restart Audacity. You should now have the “Apple: AUPeakLimiter” in the Effect menu. The way this works is a bit odd. You set the “pre-gain”, the effect amplifies the sound by that amount then applies fast hard limiting (not clipping) at 0 dB. Based on the screen shot you could start with a pre-gain of 6 dB. If that is not enough, undo and try again with a higher setting.
If you check the time scale on the screen shot it’s about 15 seconds per centimetre, so those “spikes” are not as transient as they first appear.
There is a 5 second audio sample a few posts back that contains one of those peaks, and the peaks are not very short - the example is about 100 milliseconds duration. I’ve not tried the Apple: AUPeakLimiter (I don’t have a Mac) but using hard limiting on this audio is likely to produce unwanted distortion, so I’d recommend using a compressor - preferably one with lookahead (such as the standard Audacity compressor). Similarly my “Soft clipping limiter” and Edgars RTF-limiter are not really suitable for this job.
@Steve: This is the problem when discussing “hard limiting” - there are many different interpretations. My experience with the AUPeakLimiter is that is uses gain reduction, not clipping, with a fast attack and release (both settable), and probably some look-ahead. So in some circles it would be called a “compressor” - one with an infinite GR ratio above the threshold and very fast attack and release.
the problem is that the compressor settings changes I have to remember to manually set it to the values you gave me (since this is an ongoing process that will continue for months), so if I have a preset that I don’t need to manually change, that makes things much less error-prone. I hope that makes sense.
I just confirmed this in Audacity 1.3.12 on Mac. I used the built-in compressor, changed all settings and applied. I quit audacity, restart audacity again, different track, used the compressor again and all the parameters were still the ones I had selected before.
stasaudio, what’s your audacity version? On which OS are you running it?
Yes, sorry, I wasn’t clear. The last setting is remembered, but if I change the setting for doing a different kind of compression while working on a different audio content, I have to manually change the settings again and since it’s not just one entry, but 5 it’s not trivial. What I’m after is having a presets that I can choose from - e.g. [compressor speech type 1] [compressor speech type 2], etc.
