How can I generate audio chirp signal ?

Hi, I need to find a frequency response of the system. I want to generate chirp audio sound from 200Hz to 10Khz. I can't understand how do it. Could you help ?

Answer 1

[Star Strider]

Try this:

t = linspace(0, 4.8, 4.8E+4);
f0 =   200;
f1 = 10000;
Fs = 1/mean(diff(t));
x = chirp(t,f0,t(end),f1);

sound(x, Fs)

figure(1)
plot(t, x)

[Alex Dashevsky]

Could you explain ? I don't understand 't' vector and Fs. Why Ts=mean(diff(t)) ?

[Star Strider]

For the time vector ‘t’ and sampling frequency ‘Fs’, see the documentation for the chirp (link) function.

The ‘Ts’ variable is the sampling time interval (time between samples, assumed to be constant). Taking the mean of the differences is one way to calculate it. The sampling frequency, ‘Fs’, is 1/Ts.

[Alex Dashevsky]

I can't understand it. I want to understand what delta of frequency of chirp. why 4.8 ?

[Star Strider]

The Answer I originally designed that code for wanted a 10 kHz sampling frequency to last for 4.8 seconds.

The code I posted is simply an example of how to produce an audio sweep ‘chirp’ signal, that is what you said you wanted.

Change the sampling frequency and other parameters to do what you want.

Example —

t = linspace(0, 5, 2.1E+5);
f0 =   200;
f1 = 10000;
Fs = 1/mean(diff(t));
x = chirp(t,f0,t(end),f1);

sound(x, Fs)

figure(1)
plot(t, x)

[Alex Dashevsky]

The frequency start from 200Hz. What is the next frequency ? Can I change the next freq ? How can I set time of play. Give me example please.

[Star Strider]

It goes from 200 Hz to 10000 Hz, as you requested.

You can set the time of play by multiplying the sampling frequency by the time you want, and putting that as the third argument to linspace.

Fs = 44100;                             % Sampling Frequency (Hz)
Tmax = 5;                               % Duration (sec)
t = linspace(0, Tmax, Tmax*Fs);
f0 =   200;
f1 = 10000;
x = chirp(t,f0,t(end),f1);

sound(x, Fs)

figure(1)
plot(t, x)

[Andrew Moss]

What is t(end)

[Star Strider]

The last element in the ‘t’ vector.

[Javier]

How would you export it to be a .wav file?

Answer 2

[Sulaymon Eshkabilov]

Just using audiowrite(), e.g.:

t = linspace(0, 4.8, 4.8E+4);
f0 =   200;
f1 = 10000;
Fs = round(1/mean(diff(t)));   % Has to be integer and thus, it has to be rounded up!
y = chirp(t,f0,t(end),f1);
sound(y, Fs)
filename = 'Chirp_Sound.wav';
audiowrite(filename,y,Fs); % Chirp_Sound.wav file is created
clear y Fs   
%%  Test the recoded *.wav file
[y,Fs] = audioread(filename);
sound(y, Fs)