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Resample recordings

Is it possible to resample a recording (as opposed to downsampling). If for instance I record at a rate of 250000 thinking there may be some high frequency bats, but in fact there are none, but there are some bird calls of interest. Then to save space and to listen to the recordings at correct pitch I would like to convert file to 48000 (just as if I had recorded at that rate in the first place). My go-to software for listening / processing audio is Adobe Audition and that does not support playing files with sample rates above 192000 - so I can't just listen to these high sample files with that. Well I am sure it must be possible, but I am not sure what software to use. I have Adobe Audition, but that will covert to a lower rate by stretching out the file. And the AM tool reduces pitch.

13 comments

13 Comments

j.j.lloyd

Jul 24, 2022

Thanks Alex

I don’t think that does what I want ?

So I recorded at 250000 to see if there were high frequency bats in the area. In fact there was not much of interest at high frequency but there was some bird calls at a few kHz. So I want to just discard the high frequencies and keep the lower frequencies- just as if I had sampled at 48000 to start with. So making a smaller more manageable file, without any pitch shift.

is that possible?

sorry if I have misunderstood

jim

Alex Rogers

Jul 24, 2022

Replying to

Yep, that’s the use case for the downsampling tool in the Configuration App and in the Filter Playground. Select 48kHz and it will generate a recording as if you had recorded at 48kHz originally on the AudioMoth rather than at 250kHz. There is no pitch shift. It resamples the higher frequency data and generates a 48kHz recording with the same over sampling that the AudioMoth would perform.

The Filter Playground also allows you to playback at a reduced speed, but that is in addition to the downsampling options.

This is a frog recording originally made at 48kHz. All the frequencies in the call are really low so this high sample rate isn't really necessary.

This recording is then downsampled to 8kHz in the Filter Playground where you can see the effect instantly.

The oversampling at 8kHz also reduces the self-noise so the background sound level is lower. The Filter Playground will let you export the WAV file at the downsampled rate so you can see what it looks like in other tools. For processing lots of files the Configuration App is easier to use and does the same thing.