Topic Twenty - Loudness and Temporal Processing

Question 1

Describe loudness and its relationship with amplitude

Answer 1

Loudness is the subjective impression of the magnitude of a sound.

It is a perceptual dimension that increases with amplitude. However, this increase is not 1:1.

Loudness tends to increase more slowly than it does intensity.

Loudness doubles with every 10 dB increase in level above 40 dB SPL. Below 40 dB SPL loudness grows more rapidly.

Question 2

What are equal loudness contours and weighting scales?

Answer 2

An equal loudness contour is a family of curves that represents the required intensity for a frequency needed to match the perceived loudness of a 1 kHz tone at a certain dB SPL. Unit = phon

Weighting scales allow us to compare the equal loudness contours at different phon.

Question 3

What is loudness summation and difference limens for level?

Question 4

Describe Moore’s model of loudness perception

Answer 4

1. Stimulus
2. Stimulus is filtered for transfer from free-field to eardrum
3. Filtered for transfer through the middle ear
4. Transformed into an excitation pattern
5. Transform excitation pattern into specific loudness
6. Calculate the area under specific loudness pattern

Question 5

What is the effect of cochlear hearing loss on loudness?

Answer 5

1. Elevation of absolute threshold
   - Loss of IHC and OHC function results in the sound level needing to be increased to reach a detectable level of vibration
2. Reduction/loss of the compressive non-linearity of the BM
3. Loss of frequency selectivity
   - Broader excitation patterns
4. Reduction or complete loss of IHCs or functional neurons at certain places within the cochlear

Question 6

What are the temporal properties of sounds and their psychophysical measurement

Question 7

What is amplitude modulation and its perception

Answer 7

Amplitude modulation is when a carrier is multiplied by another sine wave

The modulation produces new spectral components called sidebands

Question 8

What is temporal resolution and the effects of hearing loss, ANSD and APD

Answer 8

Temporal resolution is the ability to detect changes over time.

Temporal resolution depends on:
- Analysis of the time pattern occurring within each channel
- Comparison of the time patterns across channels

For individuals with HL, ANSD and APD, they tend to show reduced temporal resolution