When I do a spectrogram in matlab / octave I can create a swept signal that looks like the RED plot line below. But how can I create a swept signal like the BLUE line in the 1st plot using the equation below.
thanks to Daniel and David for getting me this far with the code is below
startfreq=200; fs=44100; endfreq=20; dursec= 10;%duration of signal in seconds t=(0:dursec*fs)/fs; %Time vector alpha=log(startfreq/endfreq)/dursec; sig = exp(-j*2*pi*startfreq/alpha*exp(-alpha*t)); sig=(sig/max(abs(sig))*.8); %normalize signal wavwrite([sig'] ,fs,32,strcat('/tmp/del.wav')); %export file specgram(sig,150,400);
How can I fix the the equation in the variable sig to get it to look like the BLUE line in the 1st plot?