Audiophonic degradation
Audiophonic degradation was a measurement by which a repeating communication degraded over time. It could be used to estimate how long a message had been being transmitted.

Investigating a red burst deep in the Beta Quadrant in 2257, the  came across a Human settlement on the distant planet Terralysium transmitting an obsolete distress call. Based on the audiophonic degradation of the message, Commander Saru was able to ascertain that the message had been playing on a loop for two hundred years. ()
Communications technology