Complex Sound Perception Flashcards
What are interaural level differences?
Move azimuth off to one side
One ear falls into sound shadow
Intensity difference between ears used as location cue
Difference may be as large as 30 dB
Affects higher frequencies
What is a sound shadow?
Sounds ae bent around the head, or are diffracted by the edge of the head
What are interaural time differences?
Difference in arrival times of the sound to each ear
neurons found in the auditory cortex and the superior olives that respond to certain interaural times differences
Affects lower frequencies
What are phase differences?
Difference in phase between two waves at a point in time
Works better for lower frequencies
What is the role of the pinna in auditory localization?
Delays/amplify some frequencies coming from certain directions/elevations
May decrease intensity of some mid-range frequencies but only if the source is behind the head
What is the precedence effect?
Present two identical sounds from two speakers in different locations
At shorter delays, two sounds are fused into one
At longer delays, two separate sounds are perceived (echo threshold)
Facilitates hearing in a complex environment
What is echolocation?
Some animals sound out ultrasonic waves and the reflections off of objects are used to locate obstacles and prey
Can people utilize echolocation?
Visually impaired people do
With practice, any blindfolded participant can do it as long as they aren’t wearing earplugs
What is reverberation?
Reflection of sound by walls, ceiling, and floor
Increases the duration of sound, also aids in localization
What is reverb time?
Time for sound to decrease to 1/1000th of original pressure
What happens if the reverb time is too short?
Music sounds dead
What happens if the reverb time is too long?
Music sounds muddy
What reverb time should concert halls have?
1.5-2.0 seconds
What is the initial time delay gap?
Reflections of sound should start to follow direct sound by no more than 20-30 ms
What happens if reflecting ceiling panels are too small and disperse?
They absorb too much low-frequency sound
What is the seat-dip effect?
Significant deterioration of bass reverberation as sound passes over rows of seats
Why are concave walls bad for concert halls?
They cause echoes and distortions
What is primitive grouping?
Continuous flow of sound is analyzed into separate chunks and groups
What are the important variables to include in a primitive grouping?
Intensity, temporal change, frequency change, location, timbre
How does primitive grouping occur?
According to:
-similar patterns over time (sequential)
-similar frequency spectra (simultaneous)
What does primitive grouping result in?
Separate auditory streams: groups of sounds that seem to belong together
What is schema-driven grouping?
Higher level knowledge guides the grouping and listening processes
Sound input is analyzed for particular patterns
What is absolute pitch?
Extreme accuracy (>90%) in identifying an isolated musical note without a reference tone
How did music evolve?
With culture
