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How to design a graphic equalizer

Started by dingke1980 August 27, 2005
I am doing a software project about a ten-band graphic equalizer. Is there
any solutions about how to design it? Currently, I have the following
ideas:

1.Use FFT, apply different gains to each frequency bin. But for low
frequency band like 31.25Hz, 62.5Hz, 125Hz, there are few frequency bins
even using large length FFT. The frequency precision is roughly
influencing.

2.Use FIR filter bank. Design ten band-pass filters, apply gains in each
band, then sum then together in time domain. But still for low frequency
band like 31.25Hz, 62.5Hz, 125Hz, the filter length will be very very
large. I don't know how to cope with this problem.

3.Use IIR filter bank. Which may greatly reduce the filter length. But
another concern appears. IIR filter is not a linear phase filter.
Furthermore, it may unstable after processing many audio frames.

Hope DSP experts can help me. :)

Thanks a lot!

		
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"dingke1980" <dingke1980@hotmail.com> wrote in message 
news:ke-dnfBT26Oi3o3eRVn-jw@giganews.com...
> > I am doing a software project about a ten-band graphic equalizer. Is there > any solutions about how to design it? Currently, I have the following > ideas: > > 1.Use FFT, apply different gains to each frequency bin. But for low > frequency band like 31.25Hz, 62.5Hz, 125Hz, there are few frequency bins > even using large length FFT. The frequency precision is roughly > influencing. > > 2.Use FIR filter bank. Design ten band-pass filters, apply gains in each > band, then sum then together in time domain. But still for low frequency > band like 31.25Hz, 62.5Hz, 125Hz, the filter length will be very very > large. I don't know how to cope with this problem. > > 3.Use IIR filter bank. Which may greatly reduce the filter length. But > another concern appears. IIR filter is not a linear phase filter. > Furthermore, it may unstable after processing many audio frames. > > Hope DSP experts can help me. :) > > Thanks a lot! > > > This message was sent using the Comp.DSP web interface on > www.DSPRelated.com