Plotting Audio signal in terms of Frequency changes

Hi I use the following code to create an audio signal that moves up and down in frequency from 200-700Hz:

frequency = freq;

Fs = 8192;

T = 1/Fs;

tmax = 40;

f1 = 200; % initial frequency in chirp

f2 = 700; % final frequency in chirp

tfinal = 1/frequency; % Duration of the period

amplitude = 0.25; % Amplitude of Signal

tHALF = 0:T:(tfinal/2 - T); % Half the time function

y = []; % Creates empty matrix for our auidio signal 'y'

y = chirp(tHALF,f1,tHALF(end),f2,'linear');

I simply want to to create a new data file using my sinewave that will show me the changes from data point to data point in terms of the frequencies (200-700), i.e my new data file will show values ranging from 200-700.

I know this may be a basic question but I have not done any audio analysis before and any help would be really appreciated.

thanks in advance,

Alan