Pitch Scaling

Pitch scaling is a technique used to change the pitch (the highness or lowness of a sound) of an audio recording without changing its tempo (speed). This can be done by increasing or decreasing the frequency of the audio signal.

Activity 5

Pitch Scaling

% Read in audio file

[y,fs] = audioread('sarigamapa.wav');

y = y(1:1000,1);

% pitch scaling factor

% 0.5 for half speed 2 for double speed

pitch_factor = 0.5;

% Length of the audio signal

n = length(y);

% Find the pitch scaling factor in samples

pitch_factor_samples = round(pitch_factor * n);

% Initialize output signal

y_pitch_scaled = zeros(n,1);

for i = 1:n

y_pitch_scaled(i) = interp1(1:n, y, i/pitch_factor);

end

sound(y_pitch_scaled,fs);

Spectrum of Orginal Signal

n = length(y);

y_fft = fft(y);

f = (0:n-1)*(fs/n);

power = abs(y_fft).^2/n;

plot(f,power,'LineWidth',1.2);

xlabel('Frequency');

ylabel('Power');

grid on

Spectrum of Pitch Scaled Signal

n = length(y_pitch_scaled);

y_scaled_fft = fft(y_pitch_scaled);

f = (0:n-1)*(fs/n)*pitch_factor;

power = abs(y_scaled_fft).^2/n;

plot(f,power,'LineWidth',1.2,"Color",'r');

xlabel('Frequency');

ylabel('Power');

grid on