Fourier transform audio files?
SoX can do this:

play file.wav stat -freq


It will output  something like this:

file.wav:

 File Size: 191k      Bit Rate: 256k
  Encoding: Signed PCM
  Channels: 1 @ 16-bit
Samplerate: 16000Hz
Replaygain: off
  Duration: 00:00:05.98

In:0.00% 00:00:00.00 [00:00:05.98] Out:0     [      |      ]        Clip:0    0.000000  0.005858
3.906250  0.006152
7.812500  0.006272
11.718750  0.006785
15.625000  0.004786
...
In:17.1% 00:00:01.02 [00:00:04.95] Out:43.0k [    -=|=-    ]        Clip:0    0.000000  0.057157
3.906250  0.004143
7.812500  1.779299
11.718750  0.120536
15.625000  0.062992
19.531250  0.059568
23.437500  0.149960
...
In:100%  00:00:05.98 [00:00:00.00] Out:264k  [      |      ]    

    Clip:0
Samples read:             95616
Length (seconds):      5.976000
Scaled by:         2147483647.0
Maximum amplitude:     0.440094
Minimum amplitude:    -0.298309
Midline amplitude:     0.070892
Mean    norm:          0.041338
Mean    amplitude:     0.000022
RMS     amplitude:     0.064054
Maximum delta:         0.529938
Minimum delta:         0.000000
Mean    delta:         0.011127
RMS     delta:         0.025654
Rough   frequency:         1019
Volume adjustment:        2.272
Done.


The ... are omitted lines, of which there are many (thousands).

These sections:

3.906250  0.006152
7.812500  0.006272
11.718750  0.006785
15.625000  0.004786


Are a table of Frequency against Level.