# why should we multiply the number of samples with sound frequency to calculate the sine wave?

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joly Alipor on 6 Jul 2020
Commented: joly Alipor on 6 Jul 2020
I have a code that aims to produce sine waves for durations of interest. in line related to creating sine wave, it's written:
tone_dur = sin(2*pi*freqs*t);
t is the number of samples needed for each tone duration and freq is the tone frequence (500 Hz). What I don't get is that why should we multiply the number of samples with sound frequency to calculate the sine wave? I don't get the rational!

Geoff Hayes on 6 Jul 2020
joly - I think that t is usually a time array (in seconds). From fft examples, t can be initialized as
Fs = 1000; % Sampling frequency
T = 1/Fs; % Sampling period
L = 1500; % Length of signal
t = (0:L-1)*T; % Time vector
Then you should be able to continue as before.
If t were just the number of samples, i.e. a scalar, then tone_dur would be a scalar value as well....and I don't think that is exactly what you want.

joly Alipor on 6 Jul 2020
Now to me t is an (1*n) array describing the time. Is it right?
interval(i), say interval(1) is 0.230 s.
Geoff Hayes on 6 Jul 2020
If interval is a time i.e. 0.230 seconds, then t, which is an array from 0 to interval(k), would be an array describing time.
joly Alipor on 6 Jul 2020
That's exactly right. Thanks a lot for your great help.