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Psychoacoustics: loudness, frequency discrimination, temporal resolution and masking
Psychoacoustics measures what the ear can tell apart: how loud a sound seems (phons and sones), the smallest difference in frequency or level, how short a gap can still be heard, and how one sound hides another. These normal values are the basis for understanding what goes wrong in cochlear loss.
Why it matters in the exam
The bank asks for normal values: the difference limen for frequency (DLF) is a few hertz at 500–1000 Hz (about 0.2–0.3% of the frequency), grows in hertz as frequency rises, and improves as level rises; the difference limen for intensity is roughly 0.5–1 dB. Adults with normal hearing detect a silent gap of about 2–3 ms in broadband noise. Temporal integration: threshold improves as a sound gets longer up to about 200–300 ms, by about 10 dB per tenfold increase in duration, and beyond that stays flat.
The second part is loudness and masking. An equal-loudness contour links tones across the frequency range that a listener judges equal in loudness to a 1000 Hz tone; the contour's phon value equals the SPL of that reference tone. The phon is the unit of loudness level, and the sone the unit of loudness — 1 sone is 40 phons, and every further 10 phons doubles the sones. The dBA scale roughly follows the 40-phon contour and discounts low frequencies, and dBC is flatter. Upward spread of masking: a loud low sound hides sounds above it more than the reverse, because its travelling wave passes through the basal region; so low-frequency noise damages consonant perception. In cochlear loss the auditory filters are broader, there is recruitment (a narrow dynamic range), and temporal resolution is often weaker.
Key points
- DLF of a few Hz at 1000 Hz; DLI of about 0.5–1 dB.
- Gap detection of about 2–3 ms.
- Integration up to about 200–300 ms, about 10 dB per tenfold.
- Phon — loudness level; 1 sone = 40 phons; dBA follows the 40-phon contour.
- Masking spreads upward; broad filters in cochlear loss.
Summary table
| Measure | Normal value or definition | Change in cochlear loss |
|---|---|---|
| DLF | A few Hz at 1000 Hz; grows with frequency, improves with level | Poorer; broad tuning |
| DLI | Roughly 0.5–1 dB | May be small because of recruitment |
| Gap detection | About 2–3 ms in broadband noise | Longer; linked to trouble with fast speech |
| Temporal integration | Improvement up to about 200–300 ms, about 10 dB per tenfold duration | Often less improvement (a flatter function) |
| Phon and sone | Phon — SPL of an equally loud 1000 Hz tone; 1 sone = 40 phons | Recruitment: loudness grows fast |
| dBA and dBC | A follows the 40-phon contour; C is flatter | Used in occupational noise measurement |
| Upward masking | Loud low sound hides high sounds | In low noise, high consonants are swamped |
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Sources
- Moore, An Introduction to the Psychology of Hearing, 6th edition (2012) — Loudness, frequency selectivity, temporal processing
- ISO 226, 2023 — Acoustics — Normal equal-loudness-level contours
- Gelfand, Hearing: An Introduction to Psychological and Physiological Acoustics, 6th edition (2017) — Psychoacoustic methods and results
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.