I use sox
Example:
sox ./OldPhone.mp3 -n stat[quote]Samples read: 442367
Length (seconds): 10.030998
Scaled by: 2147483647.0
Maximum amplitude: 0.618559
Minimum amplitude: -0.568570
Midline amplitude: 0.024994
Mean norm: 0.083623
Mean amplitude: -0.003463
RMS amplitude: 0.117218
Maximum delta: 0.628859
Minimum delta: 0.000000
Mean delta: 0.028367
RMS delta: 0.045607
Rough frequency: 2730
Volume adjustment: 1.617
[/quote]