[LAU] Recording with TimeMachine

I've been using TimeMachine to record late night music radio programmes. I'm pretty sure I didn't do anything different, but one recording is significantly quieter than the others and the quiet one shows up as of type 'Unknown (model/x.stl-binary)' in Nemo file manager, whereas the good ones are of type 'Binary (application/octet-stream)'. 'file' says they are all Sony Wave64 RIFF data, WAVE 64 audio, stereo 48k sox (-n stat) seems to show significant differences: Good Quiet Samples read: 676507136 666574336 Length (seconds): 7046.949333 6943.482667 Scaled by: 2147483647.0 2147483647.0 Maximum amplitude: 0.999969 0.999969 Minimum amplitude: -0.920116 -0.999969 Midline amplitude: 0.039927 0.000000 Mean norm: 0.154645 0.051673 Mean amplitude: -0.000065 -0.000022 RMS amplitude: 0.199364 0.066460 Maximum delta: 1.421344 1.754726 Minimum delta: 0.000000 0.000000 Mean delta: 0.090457 0.034210 RMS delta: 0.134921 0.048614 Rough frequency: 5170 5588 Volume adjustment: 1.000 1.000 Any idea what could have gone wrong? What would be the right way to calculate the value to use with sox -v to get the volume level somewhere near that of the 'Good' recording? -- Thanks, John.