Generate acoustic signal with difference rise time and fall time

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BoWen Han
BoWen Han 2022-3-11
评论： Scott MacKenzie 2022-3-15
Hi
Can someone help me for this one? I would like to plot a signal that can be similair with acoustic emission signal with difference rise time and fall time. There is not specific parameters but I just want to know if there's a way to generate?
Thanks
  2 个评论
Scott MacKenzie
Scott MacKenzie 2022-3-11
Just to clarify, by "rise time and fall time", do you mean adding an envelope to an existing signal so the amplitude rises from 0 to max over some period time at the beginning of the signal and falls from max to 0 over some period of time at the end of the signal?
BoWen Han
BoWen Han 2022-3-14
Hi sorry for late reply. Yes that is exactly what I mean and thanks for your advise for envelope !

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Scott MacKenzie
Scott MacKenzie 2022-3-14
编辑：Scott MacKenzie 2022-3-14
Ran in:
Here's a simple approach that provides separate control for the rise or attack time (n1), the sustain time (n2), and the decay or fall time (n3):
f = 440; % Hz (cycles per second)
duration = 2; % seconds
sRate = 8192; % default
sInterval = 1/sRate;
% vector for values of t at each sample point
t = 0:sInterval:duration;
n = length(t);
% build the waveform vector
y = sin(2*pi * f * t);
% build envelope (tweak as desired)
n1 = 100; % attack
n2 = 200; % sustain
n3 = 500; % decay
n4 = n - (n1 + n2 + n3); % off
attack = linspace(0,1,n1);
sustain = ones(1,n2);
decay = linspace(1,0,n3);
off = zeros(1,n4);
envelope = [attack sustain decay off];
% apply envelope to signal
y = y .* envelope;
% play it
soundsc(y, sRate); % NOTE: sRate not needed if 8192 (default)
% plot the first few cycles of the waveform
plot(y(1:1000));
set(gca, 'ylim', [-1.5 1.5]);
title('Envelope Demonstration');
xlabel('Time'); ylabel('Amplitude');

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