how to make distance affect on attenuation factor?

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HUIHSUAN
HUIHSUAN 2024-5-11
评论： Mathieu NOE 2024-5-14
This is so far my distance effect function, but the attenuation factor(Att_linear) doens't work with input signal(inwave_lowpass) arrays have incompatible sizes for this operation, I tried to use convolve to solve it, but it will make the output (attenuated_signal) sounds like broken noise. I also tried filter(Att_linear, 1, inwave_lowpass) but it make the output sounds like broken also.
[inwave,fs]=audioread("anechoic_voice.wav");
%LOW-PASS FILTER%
% Define filter specifications
cutoff_frequency = 20000;
sampling_frequency = fs;
filter_order = 4;
%matlab lowpass filter
inwave_lowpass = lowpass(inwave,cutoff_frequency,sampling_frequency) ;
%ABSORPTION context%
%citing dissipation function by Densil C.(2015)
%alpha=absorption coeff (dB/m)
f_desired=(20:20000);
alpha = dissipation (f_desired, 20, 50,100,1);
%definie destination
r=1;
%decay factor in dB
Att=alpha.*r;
% Convert attenuation factor to linear scale
Att_linear = 10.^(Att/20);
% Apply attenuation to the input signal%
%attenuated_signal =inwave_lowpass.*Att_linear; %Problem: .*not work cuz arrays have incompatible sizes for this operation.%
attenuated_signal =conv(inwave_lowpass,Att_linear);%Problem: convolve not work for r when output.%
% Plot the frequency response of the attenuation filter
freqz(Att_linear, 1, 1024, fs);
% Play the attenuated signal
sound(attenuated_signal, fs);
Thank you for your time!

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采纳的回答

Mathieu NOE
Mathieu NOE 2024-5-13
hello again
try this corrected code :
[inwave,fs]=audioread("anechoic_voice.wav");
%LOW-PASS FILTER%
% Define filter specifications
cutoff_frequency = 20000;
filter_order = 4;
%matlab lowpass filter
inwave_lowpass = lowpass(inwave,cutoff_frequency,fs) ;
%ABSORPTION context%
%citing dissipation function by Densil C.(2015)
%alpha=absorption coeff (dB/m)
f_desired=linspace(0,fs/2,100); % frequency vector must go from 0 to fs/2;
alpha = dissipation (f_desired, 20, 50,100,1);
%define distance
distance = 1;
% Generate a FIR filter for dissipation (code copied from inside the
% function)
magnitude = 10.^((-alpha * distance) / 20);
filterlen = 16;
h = fir2(filterlen,f_desired(:)/(fs/2),magnitude(:)); % h = FIR coefficients
% Plot the impulse response of the attenuation filter
figure,plot(h);
% Apply attenuation to the input signal%
attenuated_signal = filter(h,1,inwave_lowpass);
% Plot the frequency response of the attenuation filter
figure,freqz(h, 1, 1024, fs);
% Play the attenuated signal
sound(attenuated_signal, fs);

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