Say you found a weird bird on the street & wanted to record it’s call. How would you remove wind & traffic noise?
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The simplest way is to filter by frequency. It’s fairly easy for even a basic hobbyist to build a filter with purely passive components that will exclude certain frequencies from a signal. Actual audio equipment can manage it much more precisely.
You can also use samples to exclude specific sounds. We can develop a mathematical model for what wind “sounds like” in terms of not just specific frequency spectrums but how those spectrums change over time. Then we match the model to our recording and figure out the highest likelihood filtering method.
We can use similar methods to identify doppler patterns – which enables us to discriminate between moving and non-moving audio sources.
If we can control the microphone, we can also use different hardware to control direction/range so that we’re primarily recording a specific point in space.
If we have multiple microphones, we can use the known properties of attenuation to isolate specific points in space and track movement in time.
From the practical standpoint of “hey, I’ve got my phone and want to record this bird…”, you’re either going to need to learn a lot of mathematical techniques (many of which are classified since the task you’ve set yourself is basically the same as trying to detect submarines) or you’ve going to want to download an app that incorporates many of those techniques.
Note: Audio engineers/producers don’t isolate sounds from recordings. They use devices invented by other people – other people with enormously more education than them about how sound works – to prevent noise from occurring in the first place. There’s a reason auto-tune was invented by a guy whose day job was studying seismic anomalies and not the guy who ensures Taylor Swift’s latest album bops.
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