[LAU] Text-based sound visualisation?

[Fons Adriaensen]

On Tue, Jun 21, 2011 at 05:48:13PM -0400, S. Massy wrote:

> I thought of that: one could split up the frequency range using a bunch
> of chains with bandpass filters, but here again, how to measure and
> report in a timely, readable matter?
> 
> I'd rather go the simplest route possible, since I don't need anything
> too fine-grained.

Before you waste too much time on this: such metering is
in general pretty useless, unless you are doing sound level
monitoring to determine acoustic pollution levels to some
official standard or something similar. And in that case
you need very strictly specified hardware, filters, meter
responses and postprocessing algorithms. 

For musical (mixing) purposes such a display may give you
the illusion of providing some interesting info but it
doesn't. 

Suppose you have a meter that displays the levels in say
ten frequency bands. How would you use its output ? Try
to make the levels equal, or fit them to some template ?
If the purpose is to find which band is responsible for
some peaks you want to reduce, forget it. Either things
will be very clear and you can easily *hear* where the
problem is, or you won't get any reliable output from
your meter at all. 

The most useless of all would be a set of linearly spaced
equal bandwidth filters as provided by a standard FFT.
The least you need for musical use is perceptual filter
set such as provided by japa. Note that japa (with its
default resolution setting) computes more than 200 
overlapping bands - way too much for any text based
display.

Ciao,

-- 
FA