Oops. Sox fails on flac and gives only 8 seconds. A50 is correct because it encoded to wav. So I used sox to convert L5 flac to wav and regenerate spectrogram. So the correct spectrogram for L5 is the following:
So they look the same except that A50 used Mono (1 channel) and L5 seems to have recorded 2 channels.
Is there another sound processing going on after the mic picks up the sound? What happens when the sound gets in the modem? My next test will be to record the audio as listened to on the A50 through cellular and reproduce the spectrogram. I just do not know how to capture the audio on Android from this device…