What would cause recordings to playback at exactly half speed?

Whether Voice Mail or System recordings, I am getting playback at exactly half speed [proven by doubling the speed using Audacity]. Since the prerecorded system announcements are playing fine, it is not really a playback problem as much as a recording problem: it is recording at double speed.

Running asterisk on a big DELL server.

This is an all SIP installation but after concerns about recording problems being caused by timing issues, I added a Digium [analog] card and it’s functioning properly.

Everything else seems to be running just fine.

What have I missed?