Topic: anchor sound (Read 2451 times)
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## anchor sound

##### 2015-06-14 14:52:55
hi

I want produce anchor from target sound, how can do it?

The standard anchor is a low-pass filtered version of the original signal with a
cut-off frequency of 3.5 kHz;

thanks

## anchor sound

##### Reply #1 – 2015-06-14 15:47:57
If you have fdesign:
Code: [Select]
`Fs = 44100;  % Sampling FrequencyN  = 2;     % OrderFc = 3500;  % Cutoff Frequencyh  = fdesign.lowpass('N,F3dB', N, Fc, Fs);Hd = design(h, 'butter');`

Then you can filter(Hd, your_signal).

Otherwise you can calculate a biquad low pass filter like this:
Code: [Select]
`w0 = 2*pi*fc/Fs;alpha = sin(w0)/(2*Q);b0 =  (1 - cos(w0))/2;b1 =   1 - cos(w0);b2 =  (1 - cos(w0))/2;a0 =   1 + alpha;a1 =  -2*cos(w0);a2 =   1 - alpha;b = [b0/a0 b1/a0 b2/a0];a = [1 a1/a0 a2/a0];`

You then filter with filter(b, a, your_signal). Q would be 1/sqrt(2) for butterworth.
"I hear it when I see it."

## anchor sound

##### Reply #2 – 2015-06-17 10:52:39
thanks for help

in mushra mention anchor made bellow instruction.

. The standard anchor is a low-pass filtered version of the original signal with a
cut-off frequency of 3.5 kHz;
The characteristics of the 3.5 kHz low-pass filter should be as follows:
fc = 3.5 kHz
Maximum pass band ripple = ±0.1 dB
Minimum attenuation at 4 kHz = 25 dB
Minimum attenuation at 4.5 kHz = 50 dB.
how can effect  Minimum attenuation at 4.5 kH z  and Minimum attenuation at 4 kHz  and  Maximum pass band ripple ?

## anchor sound

##### Reply #3 – 2015-06-17 11:07:41
Oh, in that case you need to change the filter design quite a bit. Look up the documentation on filter design. You can specify pass- and stopband and attenuation etc.
"I hear it when I see it."

## anchor sound

##### Reply #4 – 2015-06-17 11:11:18
ok
I look at f design low pass filter,but I see one stop band in design.
I want use two mininmum attention mention at 4 kHz and 4.5 kHz.
how can this do?

## anchor sound

##### Reply #5 – 2015-06-17 11:55:52
Depending on the filter type you'd just pick one of these for a lowpass and then increase the filter order if necessary to satisfy the other requirement.

Or just start with the cutoff frequency and fixed order which you then increase.
"I hear it when I see it."