Subject: Re: [linux-audio-user] recording bats?
From: Dan Mills (dmills_AT_spamblock.demon.co.uk)
Date: Tue Nov 09 2004 - 01:33:54 EET
On Monday 08 November 2004 21:01, Cornell III, Howard M wrote:
> Remember, you have to sample at a rate least twice the highest frequency
> of interest. The data suggests you need the at least 192 kHz rate to
> record 96kHz fundamental signal. Plus the special microphone.
A minor niggle but in some circumstances (and this might be one of them) it
can matter, you only need twice the Bandwidth of the signal being recorded,
NOT Twice the highest frequency!
For all practical purposes in audio applications these are equivalent, but
there are cases where subsampling a signal is interesting. For example if I
have recorded a ultrasonic source using a 192Khz SR and I know that the
source is between say 50 & 60 Khz then I can bandpass filter in the DSP and
sub sample the output of the BPF at just above 20Khz (say 24K) which reduces
the amount of data I need to store WITHOUT losing any information that was
present in the original signal.
This is kind of cool for playing with sonar where the DSP requirements for
signal correlation get really silly if you work at the input rate.
Regards, Dan.
This archive was generated by hypermail 2b28 : Tue Nov 09 2004 - 01:37:03 EET