Frequency modulation to a digital signal

So I have a digital sound signal that i am trying to have its frequency being modulated by a sinusoidal waveform. I tried to used the following code to create the effect but then realize that all it does is moving samples around creating noise rather than creating the effect that i wish to create does anyone have any idea how to create a piece of code to apply FM to a digital audio file?

[x,Fs]=audioread('Guitar sample file.wav');
duration = size(x);
index = 1 : length(x);
time_delay = 0.04;
delay = ceil(time_delay*Fs);
Fc = 20;
a= 1;
b= 1;
modulation_argument = 2*pi*Fc/Fs
;
for i= delay+1:1:duration
    modulation(i)=sin(modulation_argument*i);
    delay2 = round(delay + modulation(i));
    d=(i-delay2);
    z(i) = a*x(d);
end;

Answer 1

[John BG]

Hi Haman

this is John BG <mailto:[e-mail] [e-mail]>

1.

do you want to use the function fmmod?

y = fmmod(x,Fc,Fs,freqdev)

https://uk.mathworks.com/help/comm/ref/fmmod.html?s_tid=srchtitle

It does the job and save you time.

Fs is the frequency of the modulating tone.

.

2.

You can shift the phase (< 1 cycle) a constant value adding the optional phase shift.

y = fmmod(x,Fc,Fs,freqdev,ini_phase)

.

3.

If interested to know more how does fmmod work then check

https://uk.mathworks.com/matlabcentral/answers/318969-fm-modulation-without-using-fmmod

.

4.

Use fmdemod to FM demodulate, either to recover signal, or just to check fmmod works ok.

.

5.

Also, perhaps you would like to switch to Simulink.

Simulink has a really powerful array of blocks for signals modulation.

.

6.

A few toolboxes that you may find interesting:

Communications Toolbox:

https://uk.mathworks.com/products/communications.html

DSP Systems Toolbox:

https://uk.mathworks.com/products/dsp-system/features.html

.

Haman

f you find this answer useful would you please be so kind to consider marking my answer as Accepted Answer?

To any other reader, if you find this answer useful please consider clicking on the thumbs-up vote link

thanks in advance

John BG

<mailto:[e-mail] [e-mail]>

[Haman Siu]

I do not have access to the fmmod function as its not included in my licence and I am working with the code for a project, so simulink is not an option for me