This creates ‘sort of’ chirp function:
[f1, f2, dur, fs] = deal(0, 1000, 2000, 8192);
tt=0:1/fs:dur; %Creates sampling window
m=(f2-f1)/(2*dur); %Calculating alpha/slope
s=2*pi*cos(m*tt.^2 +f1*tt);
soundsc(s,fs)
spectrogram(s,1024,[],1024,fs,'yaxis')
What do you want to create?