How can I find the actual frequency given a normalized frequency? Suppose that we have  some sample:

y =

   31.2241
   -5.9830
   22.6058
   -2.2309
  -42.8272
   29.2850
   -6.2652
   20.8502
   -2.4639
  -44.7525
   30.1104
   -6.0180
   21.4476
   -1.5089
  -45.1826
   29.2744


and somehow I know that it is obtained via a sinusoidal method which contains two sine functions at different frequencies and amplitudes, so I apply the music method:

pmusic(y,4)


and obtain the plot:



I know the location of peaks at the normalized peaks, but I don't know the actual frequency.  How can I find it? 

I know the formula is $\frac{\text{normalized frequency}*f_s}{2}$, but what about $f_s$?  Can I find it?
[Y,FS,NBITS]=wavread(FILE) returns the sample rate (FS) in Hz and the number of bits per sample (NBITS) used to encode the data in the music file.

After that, [S,F] = pmusic(Y,4,F,FS) to compute the pseudospectrum at frequencies F in Hz.