Topic Twenty-One - Auditory Localisation Flashcards
(5 cards)
Describe the mechanisms the auditory system uses to localize sound in azimuth, elevation and distance
Azimuth
- Interaural time differences
- Interaural level differences
Elevation
- Spectral differences from HRTF
Distance
- Relative loudness
- Influence of reverberation
Describe how sound localisation in the horizontal plane is achieved with reference to the cone of confusion
The Lateral superior olivary complex analyses the ILDs (above 1500 Hz)
- The sound reaches both the right and left LSO. There is inhibition and excitation that increases the difference in levels between the two sides
The medial superior olivary complex analyses interaural timing differences for localising low frequency sounds (below 1500 Hz).
- The sound reaches both the right and left MSO. There is inhibition and excitation that increases the difference in timing between the two sides
Because the interaural time differences are best for low frequencies and the interaural level differences are better for high frequencies, there is a range around 3000 hz where the sound localisation is not as good.
How do pinna cues and head-related transforms enable us to distinguish up from down and front from back?
There are interference patterns generated by reflections from the inside of the pinna which cause multiple peaks and dips in the spectrum that change with changing elevation
How do we locate sounds across the azimuth
Interaural time differences
1. There is a difference in the time taken for sounds to reach detectors that are separated in space
Interaural level differences
1. Sounds at the further ear have traveled further and are less intense
- The head produces a shadow
How is sound localization achieved in regards to distance?
The intensity of the sound becomes less intense as the distance increases
Distant sounds are more muffled due to the high frequencies being absorbed by more air
Proportion of direct versus reflected/reverberant sound
Doppler effect
