Chapter 2 of Moore (1989)

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Loudness Perception

Scope

The Extremes of Loudness Perception

The rms pressure variation at threshold for a 3000 Hz tone: 40μPa, or 0.00625 nm in displacement.
The maximum intensity without damaging the hearing is about 120 dB.
The dynamic range of 120 dB corresponds to an intensity ratio of 1: 1000,000,000,000 !

Methods for Determining Thresholds

As to how the physical intensity is measured: (1) minimum audible pressure (MAP). (2) minimum audible field (MAF).
As to how the response is collected (at all levels): (1) magnitude estimation. L= kI 0.3 (40 dB SPL 1000 Hz = one sone) (2) match the loudness of a given tone to that of a standard. (when the standard is a 1000 Hz tone, the unit is called 'phon').

Audibility Curves and Equal-loudness Contours

Audibility Curves: See Fig. 2.1
Possible reasons for midrange sensitivity: (1) Outer ear enhancement (1-9kHz, 15 dB gain at 3K Hz). (2) Middle ear transmission efficiency.
Equal-loudness Contours: Fig. 2.4
Why your stereo has a 'loudness' button?
Sound level meters: A (40 phons); B (70 phons) and C (no weighting).(Caveats: for steady, narrow band sounds only; in SPL.

Dependence of Loudness on Duration

Perfect temporal integration: I * t = k.
In reality: (I-IL) * t = IL * t = k.
Think about it: Fig. 2.5 What causes the rising and the falling phase of the curve? (a point we shall return in the next session)

Detection of DI and the Coding of Loudness

For wideband or bandpass noise, Weber's law generally holds over a wide range of intensities.
Why we are equally sensitive to DI across all levels?
Spread of excitation theory. Fig. 2.6. How to test it? Bandstop masking noise.
Phase locking theory.
Recent accounts: Why we are doing so poor instead of so excellent a job in loudness discrimination?

Weber's Law and the Near Miss

DI/I = k or constant j.n.d in dB (10 log [(I+ DI )/I])
For pure tones, the more intense the sound level, the smaller the DI becomes.
Possible reasons: (1) Nonlinear growth of the high frequency side of the excitation pattern (Fig. 2.7) . (2) Pooling of channels.

Adaptation and Fatigue

Are they referring to the same thing? Maybe not.
Fatigue as seen in TTS is affected by (1) Intensity of fatiguing stimulus, (2) Freq. of the FS (Fe), (3) Freq. of the TS (Ft), (4) Duration, (5) Time to measure. Fig. 2.8, 2.9

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