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Hi all,

I have a question regarding subband decomposition of a sound signal. 
I was looking at a beat detection algorithm and the first step is a 
frequency filterbank that splits the signal into 6-8 frequency bands. 
However, upon looking at the code I found that they work on data in 
the time domain only. is it not necessary to perform a DFT on the 
sound input first before they can perform such subbanding?

They talk about using a filterbank of bandpass filters. I am pretty 
new to this stuff. It would be great if someone could point to a 
resource that explains the process in more detail.

I am very new to DSP and would appreciate any help that anyone can 
give me in understanding this. 

The papaer is really interesting and can be found at:
http://web.media.mit.edu/~eds/beat.pdf

Pankaj
	

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From: "daga_pankaj" <daga_pankaj@daga...>
> Hi all,

Hi!

> I have a question regarding subband decomposition of a
> sound signal. I was looking at a beat detection algorithm
> and the first step is a frequency filterbank that splits the
> signal into 6-8 frequency bands. However, upon looking at
> the code I found that they work on data in the time domain
> only. is it not necessary to perform a DFT on the sound
> input first before they can perform such subbanding?

In short, no. Filtering can just as well be done in the time domain as
in the freq domain.The reason to use the DFT in its FFT incarnation is
that it's more efficient than time domain convolution for high-order
filters, ie. long impulse responses.

> They talk about using a filterbank of bandpass filters. I am
> pretty new to this stuff. It would be great if someone could
> point to a resource that explains the process in more detail.

A bandpass filter is specified by an upper and a lower frequency, or a
center freq and bandwidth. As you would expect of a filter,
out-of-band stuff is suppressed. A filterbank consists of multiple
bandpasses in parallel whose passbands combine to cover the freq
region of interest.

> I am very new to DSP and would appreciate any help that
> anyone can give me in understanding this.

Here are some nice sources:
http://www.dspguru.com/info/faqs/index.htm
http://www.dspguide.com
http://www-ccrma.stanford.edu/~jos/filters/

If you have a question it's always a good idea to search the archives.
http://shoko.calarts.edu/~glmrboy/musicdsp/musicdsparchives.html
http://groups.google.com/groups?ie=UTF-8&group=comp.dsp

> The papaer is really interesting and can be found at:
> http://web.media.mit.edu/~eds/beat.pdf
>
> Pankaj
	Martin
	

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