APP2	AirPods Pro (2nd generation)
APP3	AirPods Pro (3rd generation)
HA	Hearing aid
HL	Hearing loss
RECD	Real-ear-to-coupler difference
REUR	Real-ear unaided response
REAR	Real-ear aided response
REIG	Real-ear insertion gain
MPO	Maximum power output
SSPL90	Saturation sound pressure level for a 90 dB input
SPL	Sound pressure level
SNR	Signal-to-noise ratio
NAL-NL2	National Acoustic Laboratories—Non-Linear 2 prescription
NR	Noise reduction
FDA	U.S. Food and Drug Administration
OTC	Over-the-counter