Question

Write a short matlab function that modifies the volume of a wavefile. The function should have the following parameters: the input wavefile path, the signed value in dB which amplifies/attenuates the wavefile, the output wavefile. Make use of the following functions: wavread (or audioread), wavwrite (or audiowrite), plot, figure, subplot. Also use "help <function>" to see the meaning and parameters of these functions. Parse the wave samples using a for loop. Plot the input wave and the output wave on the same figure to see the difference.

Answer 1

The .wav file was downloaded from the internet. The function audioread returns the signal values as well the sampling frequency. audiowrite writes the data to the audiofile specified. The signed value is given in dB, which is converted into a decimal value and the signal is attenuated or amplified accordingly.

The matlab code is as follows:

function aud=aud_vol(in_path,sig_val,out_path);
[y,fs] = audioread(in_path); % Reading the audio file
y_1=y(:,2);
info=audioinfo(in_path); % Getting the info of audio file
t=0:seconds(1/fs):seconds(info.Duration);
t=t(1:end-1);

fac=10^(sig_val/20); % Conversion from dB as sig_val is in dB
aud=y_1*fac;
audiowrite(out_path,aud,fs) % Writing audio file

subplot(121)
plot(t,y_1)
title('input signal')

The output is obtained is as follows:

The signed value is given as 3 dB which is 1.5 in numerical terms. Hence the signal is amplified 1.5 times as we can see in the output plot in the right side.