Lecture 17 Flashcards
Azimuth
The angle of a sound source relative to the centre of the head
Interaural Time Differences
The difference in time between a sound arriving at one ear versus the other
-listeners can detect interaural delays of as little as 10 microseconds
Physiology of ITD
Coincidence detector neurons in the superior olive are tuned to detect different ITD’s
-These neurons will only activate action potentials if they receive a neural signal from the right and the left at the same time
Interaural Level Difference (ILD)
The difference in level (intensity) between a sound arriving at one ear versus the other
-Problem : can’t tell us how far away an object is on a given azimuth
Inverse Square Law
The intensity of sound decrease as a function of the inverse of the square of the distance
-if you double the distance (x2), you divide the sound by 4 (./. 4)
-sound decreases with distance
Spectral Composition of Sound
Changes with distance
Distal sounds have more reverbarated than direct energy
-long wavelengths are always more resistent to obstacles
-sources that are far away are likley to have encountered more obstacles
-the intensity of higher frequencies decreases as a function of distance
Cones of Confusion
Makes us realize ITD isn’t that precise
-Solution 1: moving your head will change the ‘‘cones of confusion’’. The only point that will retain its ITD and ILD is the ‘‘real source’’
-Solution 2: the pinna slightly distorts the amplitude of certain frequencies as a function of elevation
Directional Transfer Function (DTF)
A measure that describes how the pinna, ear canal, head, and torso chaneg the intensity of sounds with different frequencies tha arrive at each ear from different locations in space
Auditory Stream Segregation
The perceptual organization of a complex acoustic signal into separate auditory events for which each stream is heard as a separate event
Grouping by frequency (pitch)
Tones that have similar frequencies will tend to be grouped together
Grouping by Time
Tones that are close together in time will tend to be grouped together
Grouping by Timber
Tones that have similar timbre will tend to be grouped together
Grouping by Onset
When sounds begin at different times they appear to be coming from different sound sources
Continuity Effect
In spite of interruptions, one can still ‘‘hear’’ a continuous sound if the gap is filled with noise. In that case the sound is perceived as continuing behind the noise. However, if the gaps aren’t filled with noise, the sound is perceived as separate ‘‘chunks’’
Restoration Effect
In spite of interruptions, one can still ‘‘hear’’ a sentence if the gaps are filled with noise. In this case, higher-order semantic/syntaxic knowledge is used to ‘‘fill in the blanks’’
