[Audacity-nyquist] Reducing the volume on part of a sound.

[RACHAEL MAREE,H. <rm...@wa...>]

Hi,

Before subscribing to the list I sent this email to the list and was =
"awaiting moderation"... I'm a bit impatient, and joined a couple of =
days later. Here's hoping that I don't get a double post.

I am a beginner to Nyquist / Lisp. That said, I am attemping to write an =
Audacity "filter" / plugin. (Hehe!)=20

Ideally I would like to select 1-2 seconds of stereo audio in Audacity, =
tell the plugin a start time (within the sample i.e. 0.5 seconds in), a =
volume reduction in %, and a reduction length. The plugin would check =
whether the start time and reduction length fall within the bounds of =
the sample then reduce only that section of sound.

Is this even possible?

Now, I know that Audacity stores the selected sound in the s variable, =
and that I'd have to write a function to do this. However, there are a =
few things I don't know...
  * I can use the (loud) function to reduce the volume, and (scale-db), =
but neither seem to work in percentages. Is there a way to find how loud =
a sound is in decibels?
  * How do I reduce the volume of a part of a sound? Do I have to change =
it to an array / vector? If so, what is the relationship between array =
members and time?

Thanks in advance for your help!

Rachael.