SoX puede hacer esto:
play file.wav stat -freq
Se mostrará algo como esto:
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.
Las ... son líneas omitidas, de las cuales hay muchas (miles).
Estas secciones:
3.906250 0.006152
7.812500 0.006272
11.718750 0.006785
15.625000 0.004786
Son una tabla de Frecuencia contra Nivel.