# Click in the beginning and end of pure tone

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Dominik Deml on 15 May 2023
Commented: Les Beckham on 21 May 2023
I am wondering why there is a kind of clicking sound in the beginning
but especially in the end of a pure tone.
What I am doing:
spl_rms = 60;
spl_p0 = 20e-6;
spl_max = spl_p0 * 10^(60/20) * sqrt(2);
fs = 20000;
fsig = 1000;
n = 0:1*fs - 1;
t = n/fs;
sig = spl_max*sin(2*pi*fsig*t);
sound(sig, fs);
What is the reason for this clicking sound in the end?
What can I do against it, so how can I modify `sig` to improve this?
##### 2 CommentsShow 1 older commentHide 1 older comment
Dominik Deml on 18 May 2023
Sorry, my fault. It is not because of Matlab, it is because of my audio device BUT I want to use Matlab to fix this problem.

Les Beckham on 15 May 2023
Edited: Les Beckham on 15 May 2023
Try adding ramps at the beginning and end to avoid the discontinuities of starting and stopping the tone.
spl_rms = 60;
spl_p0 = 20e-6;
spl_max = spl_p0 * 10^(60/20) * sqrt(2);
fs = 20000;
fsig = 1000;
n = 0:1*fs - 1;
t = n/fs;
sig = spl_max*sin(2*pi*fsig*t);
ramp = linspace(0, 1, 200);
sig(1:200) = sig(1:200) .* ramp;
sig(end-199:end) = sig(end-199:end) .* flip(ramp);
tiledlayout('Horizontal', 'TileSpacing', 'compact')
nexttile
plot(sig)
xlim([1 500])
grid on
nexttile
plot(sig)
xlim([19500 20000])
grid on
% sound(sig, fs);
Les Beckham on 21 May 2023
You are quite welcome.