Quasi-peak detectors play an important role in electromagnetic compatibility (EMC) testing of electronic equipment, where allowed levels of electromagnetic interference (EMI), also called radio frequency interference (RFI), are given with reference to measurement by a specified quasi-peak detector.
This was originally done because the quasi-peak detector was believed to better indicate the subjective annoyance level experienced by a listener hearing impulsive interference to an AM radio station.
The peak detector is a rectifier followed by a low-pass filter to extract a baseband signal consisting of the slowly (relative to the receiver centre frequency) time-varying amplitude of the impulsive oscillation.
For example ITU-R 468 noise weighting uses a special rectifier incorporating two cascaded charging time constants.
In every case the dynamics are chosen to reflect the sensitivity of human hearing to brief sounds, ignoring those so brief that we do not perceive them, and weighting those of intermediate duration according to audibility.