[LAU] Analysis of monophonic audio signals on the commandline

Fons Adriaensen fons at linuxaudio.org
Sun Feb 27 09:50:29 CET 2022

On Sun, Feb 27, 2022 at 01:06:25AM +0100, Jeanette C. wrote:

> I am looking for tools to analyse bird song. I have many recordings, which
> can probably be cleaned up enough to have single calls as good as isolated.
> On the other hand there are quite a few sonograms of bird calls, used to
> identify species.

The sonogram is probably the tool of choice here. Mathematically it's quite
simple (compared to some other methods), but the entire interpretation is
left to the eye and brains of the user. It's little more than a transformation
that makes this interpretation easier.

If probably also does not reveal anything that you couldn't just hear,
just allows to put some numerical values on those features.

> What I am looking for is a kind of mathematical analysis tool to get an idea
> of frequency and volume, perhaps with an estimate of curves. I suppose that
> requires statistical analysis.

I think there are three aspects to this:

1. Understanding the maths. Some signal analysis methods are simple, some
are absolutely not.

2. Finding a tool to do the maths. This is probably the easiest part. 
My preference for that has been python + numpy + scipy for a long time.
The advantage of those is that you have a general purpose programming
language as well as tools for signal processing. This can make the 
third part a lot easier.

3. Present the results in way that is accessible to you. This will very
probably mean some data reduction, or algorithms that look for specific

A sonogram is a 2D picture. Curves for e.g. frequency or amplitude as
a function of time can be reduced to 1D, probably making the presentation

I know of experiments with a 2D 'bed of needles' (like a Braille display
but 2D) that with some training allows blind people to 'see' images.
This is probably beyond reach.

How useful would it be to present a relatively low-res image as ascii-art ?
Or a function of time as one line of ascii ? Other formats ?



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