Outline: Loudness Perception and Critical Bands

Detection

Audiogram

Minimum audible pressure (headphones)

Minimum audible field (loudspeakers)

Presbycusis - loss of 7 dB at low frequencies, up to 50 dB at 5 KHz and above, 1 Hz per day!

Loudness

Equal loudness contours

Phons scale - dB of equivalent 1 KHz tone

Sones scale - magnitude estimation

Stevens power law: S = k I^0.3

1 sone = 40 phon

10 dB increase is twice as loud

Temporal integration (like Bloch's law in vision, integrates over 100 ms)

Bandwidth

Total energy within a critical band

Greater summation across than within critical bands

Discrimination - Near miss to Weber's Law for tones

Loudness coding

More spikes, but: limited dynamic range of cells

More cells: recruitment of mistuned cells at high intensities

Adaptation (moderate levels) and fatigue (high intensities)

Adaptation - drop in perceived loudness while tone is present

Fatigue - can last over a day for very intense sounds