Generating high frequency sine waves - weird amplitude modulation
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florian schertenleib
on 21 Sep 2020
Commented: florian schertenleib
on 3 Nov 2020
EDIT: I added another example as a zip-file of a figure: 100Hz to 10kHz, sampled at 48.4kHz. You can see prominent amplitude dips at 8kHz and 9600kHz. These amplitude effects are getting even worse with slight deviations from common sampling rate, e.g.19.99kHz instead of 20kHz.
Dear All,
I am supposed to generate sine wave signals for auditory stimulation in a range of 100Hz to 10kHz.
This is my code so far:
fs = 44100; % sampling rate
duration = 100; % in ms
values = 0:1/fs:(duration*1e-3);
stimsignal = []; % pre-allocate variable
for i= 1:100
stimsignal = [stimsignal zeros(1,round(fs*0.01)) sin(2*pi*i*1e2*values)]; % create signal train of 100ms sine wave chunks, 100 Hz up to 10kHz
end
It works all right, but as a result, the sine wave chunks higher than 800 Hz show weird amplitude modulation patterns. Can anyone give me some explanation for this and how to avoid it? Any alternative matlab function? OR is it a result of the Nyquists sampling theorem and it's there anyways... so you can only reduce it by increasing sampling rate?
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/363904/image.png)
Thanks in advance,
Florian
2 Comments
Accepted Answer
Mathieu NOE
on 3 Nov 2020
hello Florian
seems I have answered the same question from the same person in this post :
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