I have made two files to test the problem I alluded to earlier:
Both files are just a 440 Hz sine wave for 5 minutes.
Here is the experiment: transfer both files to your phone. Start playing the 44.1 kHz one, turn off the screen. It sounds the same with the screen off and on, right?
Now try with the 48 kHz file. As soon as I turn off my screen, the sound starts to crackle and pop!
As some podcast-producers distribute 48 kHz-files, this is quite annoying; and it took me a while to find, because it only starts when the screen is turned off.
I wonder where the correct place to report this bug is?
A comment in the first report notes that if you turn on the equalizer (in the "Play Music" app, choose "Sound Effects" in the top menu), the problem disappears. This work around works on my phone, but...