how to make distance affect on attenuation factor?

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HUIHSUAN 2024-5-11

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https://ww2.mathworks.cn/matlabcentral/answers/2117686-how-to-make-distance-affect-on-attenuation-factor

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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Mathieu NOE 2024-5-13

we cannot run your code because you did not provide the function dissipation

HUIHSUAN 2024-5-13

https://github.com/densilcabrera/aarae/blob/master/Calculators/Propagation/dissipation.m

oh my god totally forget it! thank you for remind! its a code from github!

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Answer 1

Mathieu NOE 2024-5-13

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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);