How can I use the chirp function to create a linear sine sweep from a given starting and ending frequency within a given time frame?

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Tyler Bisson 2016-12-13

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https://ww2.mathworks.cn/matlabcentral/answers/316757-how-can-i-use-the-chirp-function-to-create-a-linear-sine-sweep-from-a-given-starting-and-ending-freq

评论： Greg Dionne 2018-1-29

How could I, for example, make a 3 second sine sweep starting at 40 Hz and ending at 10 kHz?

The examples given in the help section for chirp have not been useful.

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David Barry 2016-12-13

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https://ww2.mathworks.cn/matlabcentral/answers/316757-how-can-i-use-the-chirp-function-to-create-a-linear-sine-sweep-from-a-given-starting-and-ending-freq#answer_247074

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% create time signal
freqSamp = 1e6;
tStart = 0;
tEnd = 3;
t = tStart:1/freqSamp:tEnd;
% create swept sine
freqStart = 40;
freqEnd = 1e4;
phaseInit = -90;
method = 'linear';
y = chirp(t, freqStart, tEnd, freqEnd, method, phaseInit);

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Atilla Golan 2018-1-29

It does work perfectly, I have two questions: 1- What is the role of phaseinit? I changed it to different values and nothing changed. 2- It is up-going linear, how we can make down-going one?

Greg Dionne 2018-1-29

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Try something like this:

t=0:0.001:2;                    % 2 secs @ 1kHz sample rate
y=chirp(t,200,1,100,'linear');  % Start @ 200Hz, cross 100Hz at t=1sec
spectrogram(y,kaiser(128,18),120,128,1E3,'reassigned','yaxis');
title('Linear Chirp: start at 200Hz and cross 100Hz at t=1sec');