R help - Dec 2003 - sound library

I'm collaborating with and electronic musician to experiment on the
production of music from number sequences. As I'm an R user I started
playing around with the sound library and I found it very useful. However there
are several things I do not understand (I'm not an expert in acustic nor
audio signal treatment).

The first thing I'd like to understand is: let s be a normalized sample and
suppose it generates a waveform with non audible frequencies. Then if I play it
trough the function "play" (I'm using an R-window version) I
won't hear anything. Then I play: play(10000*s) and I can hear something.
What is happening to the audio sample?

I saved as wave files both s and 10000*s and then with my musician friend we
looked at the waveforms we got.
They are totally different from each other and we couldn't fidure out which
transformation of s generated the 10000*s waveform.

Can anyone explain what is going on?

Thanks in advance

Giovanna Jona Lasinio

giojona at libero.it wrote:
> I'm collaborating with and electronic musician to experiment on the
production of music from number sequences. As I'm an R user I started
playing around with the sound library and I found it very useful. However there
are several things I do not understand (I'm not an expert in acustic nor
audio signal treatment).
> 
> The first thing I'd like to understand is: let s be a normalized sample
and suppose it generates a waveform with non audible frequencies. Then if I play
it trough the function "play" (I'm using an R-window version) I
won't hear anything. Then I play: play(10000*s) and I can hear something.
What is happening to the audio sample?
Looks like it is not checked whether the generated "sound", i.e. a
wave
file, is valid. Using 16 bit resolution, you cannot have more than 2^16 
integers, but 10000*s contains invalid integers for the wave representation.

> I saved as wave files both s and 10000*s and then with my musician friend
we looked at the waveforms we got.
> They are totally different from each other and we couldn't fidure out
which transformation of s generated the 10000*s waveform.
Since you are writing invalid values to the file, those are interpreted 
in the "wrong" way and you might get something different.

> Can anyone explain what is going on?
Two more comments:
"sound" as is does not pass Rcmd check on Windows (because Media
Player
is not available on the system I do compile on, etc.) and has some more 
deficiencies. It's only available as a Windows binary on CRAN because of 
my personal interest in the package.
The author of the package, Matthias Heymann, has been informed, but he 
is not going to fix the bugs in the near future, unfortunately.

I am planing to write a package for the analysis of music (including 
loading / playing / saving wave files) next year myself.

Uwe Ligges


> Thanks in advance
> 
> Giovanna Jona Lasinio
> 
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