Audacity Forum

Is it out of the scope of the Sound/Silence Finder to suggest adding the ability to find particular kinds of sounds? The current tools are aimed at detecting boundaries between sound and no sound, with the only fine tuning being what level is considered to be silence. I assume it's mainly designed for marking gaps between songs.

I'm suggesting adding the ability to find a sound with particular FFT characteristics. E.g. add a label at every point where a particular bandwidth has at least a particular level for at least x milliseconds.

I haven't thought much about what sort of parameters would be needed - maybe just a frequency range and a level range, perhaps a FFT window size. If you could contemplate adding this then I'll have a better think about it, otherwise I'll think about writing my own (maybe, assuming it's even possible). The kinds of things it could be used for are possibly so different to the normal use of this command that it might belong in its own plugin, and enabling it would require FFT to be calculated for the whole selection, so it could be very much slower than the normal use.

pshute wrote:The current tools are aimed at detecting boundaries between sound and no sound, with the only fine tuning being what level is considered to be silence. I assume it's mainly designed for marking gaps between songs.

I believe that the original reason for this effect and its main use is to mark tracks between songs, though there have been some widely diverging examples of its use that have come up on the forum. One user was wanting a modification that would allow him/her to distinguish between vocal sounds of animals from other environmental sounds (animal behaviour research). A marine biologist was wanting to mark sounds of killer whales in many hours of hydrophone recordings. Another user had recordings from a messaging system with "beeps" between each message and was wanting to mark the beeps. I am constantly amazed by what people use Audacity for

pshute wrote:I'm suggesting adding the ability to find a sound with particular FFT characteristics. E.g. add a label at every point where a particular bandwidth has at least a particular level for at least x milliseconds.

This sounds quite similar to the "beep detection" case. What we ended up doing there was to make a copy of the track and apply a very narrow band-pass filter to it at the "beep" frequency. This removed most of the audio other than the beeps, which were then easily detected with the (unmodified) Silence Finder.

pshute wrote:I'm suggesting adding the ability to find a sound with particular FFT characteristics.

Nyquist is capable of FFT analysis, but unfortunately my knowledge of FFT is very limited and implementing FFT in Nyquist plug-ins is rather complicated. If you are interested in investigating this area there is an FFT tutorial for Nyquist programming here: http://www.audacity-forum.de/download/e ... torial.htm

Steve,

is this a project you are actively working on? Or are you planning to develop a proposal?

Whichever way I don't think I need to transfer it to Wiki>PFR - but I will xfr it to the FR archive page here on the forum if you need it for reference - please advise.

Thanks,
Peter.