This signal is what is sometimes called XM (ENIGMA oddity designation), Backwards Music, or Whales. Recently I also saw it called (tongue in cheek I am pretty sure) Backwards Whales. There are several theories on what it is, ranging from encrypted traffic to simple feedback.
The signal can show significant variation from source to source. Antenna bearings suggest many locations have been the source for this signal. It is sometimes noted on USN frequencies, and so that is one theory for source, but it can also show on freqs the USN is not known for using. If the signal is accidental that could confuse things even more, since it might be from multiple sources at different times and folks often try to tie a signal to one source.
This signal shows up periodically, and has for many years. Sometimes it is on a freq for a few minutes or hours, other times it will be on a freq for days or even weeks. It had been on the freq you recorded for at least 2 days before your recording.
Personally I think it is feedback, a transmitter or open microphone monitoring a receiver tuned to its own transmit frequency, either via a remote or local. Although very uncommon, background noises have occasionally been noted on the signal.
T!