Audibility

Audibility is the ability to perceive sound through the auditory system. It describes the boundary between sounds that can be detected and those that remain inaudible, given a listener, their hearing health, and the listening environment. In practical terms, audibility concerns whether a sound rises above the listener’s threshold of hearing and is sufficiently salient to be recognized.

Human hearing spans roughly 20 Hz to 20 kHz, though sensitivity varies with frequency, age, and individual health. The threshold of hearing for a young, normal-hearing listener is often cited as 0 dB SPL at 1 kHz, but thresholds differ across frequencies and listeners. Loudness perception is related to but not identical with sound pressure level; equal-loudness curves describe how sensitivity changes with frequency and level.

Audibility is influenced by several factors, including the sound’s level, frequency content, and duration; the presence of masking sounds; background noise; reverberation; and the listener’s attention and cognitive state. Masking occurs when a louder sound makes a nearby sound harder to hear. Hearing loss, age, and health conditions can raise the audible threshold, reducing audibility for many sounds.

Measurement and assessment of audibility employ psychoacoustic testing and audiometry to determine hearing thresholds, while technical evaluations use sound level meters and models of masking. Applications span audio engineering, safety signaling, environmental noise assessment, communication design, and clinical audiology, where understanding audibility informs device design, standards, and interventions.