Duilio,

Depending on what frequencies you are trying to filter out and those of
interest........
You could implement a lowpass, highpass or bandpass filter.
This could be done quite simply with an op-amp and approximately 2 resistors
and 2 capacitors for the lowpass or highpass.  Double the hardware just
mentioned and combine the two for a bandpass filter.
This is all for a single voltage power supply.
If you have a dual polarity power supply you could do a bandpass filter with
just one op-amp.

David


----- Original Message -----
From: Duilio Foschi <foschid@SHUTTLE.ETRURIA.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, March 09, 2000 7:47 AM
Subject: recording w/o noise


> I am preparing a tutorial for my new application using Lotus' ScreenCam.
>
> I have done all the video recording and now have to add the voice track.
>
> This is easily done (at least in theory) using the mic attached to the
> sound card of my PC.
>
> The problem is:
>
> all sort of noises enter my room from down the street and in all the tests
> I made the noise is well audible in the recorded track.
>
> Still I have all my things here and would hate to migrate to a different
> place.
>
> Also I guess that if I don't rent a professional recording room - what
> would be expensive and troublesome - I will find noise - more or less -
> everywhere.
>
> Is there a hw solution (a special mic ?) to filter out the noise when
> recording and/or a sw solution (Goldwave ?) to filter out the noise from
> the WAV file after the recording ?
>
> Thank you
>
> Duilio Foschi
>