Review

Question 0

Localization distance cues

Answer 0

Distance perception in audition depends on three main factors. The sound pressure
decreases proportionally to the distance between the listener and the sound source.
So if you double the distance, you decrease the pressure by 6 dB. Also, as a sound
source moves further away from a listener in an environment where there are variousobjects around that reflect sound, the ratio between the sound level coming straight
from source to the listener and the sum of all the sound levels from the same sound
bouncing off of all the objects (the reverberation) decreases. Finally, molecules in the air can absorb sound waves that are small (high frequencies), so sounds that are
further away have more and more absorption of high frequencies, or filtering. So
sounds further away sound softer, less bright and feature more echoes.

Question 1

Localization

Inter aural level difference.

Answer 1

Differences in level between the two ears are greatest for high frequencies whose
wavelengths are smaller than the diameter of the head, because the head casts an
acoustic shadow for these wavelengths, whereas longer wavelengths simply wrap
around the head. Note that the ILD is only about 8 dB at 1000 Hz and is negligible at200 Hz.