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phonometry

Psychoacoustics

By José M. Requena Plens · Published , updated

Psychoacoustics replaces the question “how many decibels?” with “what does the listener perceive?”. Its base quantity is loudness: a perceptual magnitude in sones, computed by auditory models that account for the ear’s filtering, masking and compression. On top of loudness sit the sound quality sensations that distinguish two equally loud sounds: sharpness (high-frequency emphasis), tonality (audible discrete tones), roughness (fast modulation) and fluctuation strength (slow modulation). And on top of those sits a combined annoyance metric that weighs them into a single scalar.

Loudness is the foundation page. It covers the three model families phonometry ships (Zwicker per ISO 532-1, Moore-Glasberg per ISO 532-2/3, and the Sottek Hearing Model of ECMA-418-2) together with the ISO 226:2023 equal-loudness contours that anchor the perceptual scale for pure tones. Sound Quality Metrics adds sharpness per DIN 45692 and the ECMA-418-2 tonality, roughness and fluctuation strength that share the Sottek front-end.

Tones in noise get two dedicated pages because two different questions are asked of them. Prominent Discrete Tones (ECMA-418-1) answers a product-noise question: is this tone prominent by the tone-to-noise and prominence-ratio criteria used in IT-equipment declarations? Objective audibility of tones in noise (ISO/PAS 20065) answers an environmental one: by how many decibels does the tone exceed its masking threshold, the audibility that feeds the tonal penalty of ISO 1996-2.

Psychoacoustic annoyance and fluctuation strength closes the chain with the Fastl & Zwicker model, which combines loudness, sharpness, roughness and the slow-modulation sensation of fluctuation strength into a single annoyance value. Read it last: it consumes everything the other pages define.

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