Complex sound Perception Flashcards
What are Interaural Level Differences in auditory localization?
if a sound comes from the right side, it will be LOUDER on our right ear and quieter on the left, this tells our brain where the sound is coming from
the difference may be as large as 30dB
this is effected by high frequencies
In terms of Interaural Level Differences, what is the “Azimuth”
the angle of a sound source
0 = in front
90 = right side
180 = behind
270 = left
What is a sound shadow
In terms of Interaural level differences, a sound shadow is the area of your head where high frequency sounds are blocked or reduced
What are Interaural Time Differences>
Where difference in arrival times tell us where a sound is coming from (if a sound reaches one ear slightly before it reaches the other, our brain will figure out where it is coming from)
Affects lower frequencies
there are neurons found in the auditory cortex and superior olives that respond to interaural time differences
What are phase differences?
Where the difference in phase times between two waves tell us about sound.
Eg, if arrival times differ by 0.5ms, the phase differnce is 180 degrees
works better for lower frequencies
What is a prime example of how the Pinna can delay or amplify some frequencies coming from certain directions/elevations
Wearing Headphones
The Pinna may DECREASE intensity of some mid-range frequencies, but only if the source is what?
Behind the head (because they kind of face forward)
Explain the Precedence Effect
If you present two identical sounds at different times we hear different things:
- at shorter delays, if its 2ms or less, the two sounds “fuse” together
- if sounds are 5-20ms of delay, sound is perceived to be coming from the leading source only
- at longer delays (35ms) we percieve the two sounds like an echo
What does precedence effects help with?
facilitates hearing in a complex acoustic environment
eg. in a cave where sounds bounce
What is Echolocation?
where an animal (or even a human) uses sound echos to locate objects
- used by visually impaired people
Explain the study done by Ammons, Worchel, and Dallenbach
-blindfolded participants
- told them to walk towards obstacles ranging from 6-30 ft
- with practice, they could locate and avoid obstacles (the obstances were moved every time)
- but not when wearing earplugs
Explain the Kellogg experiment
- a wooden disk was placed 20 ft away from participants
- the disk was moved further and closer and blindfolded participants had to guess where it was, they were allowed to make noise to determine the distance
- differences of 2 feet were reliably made
What is Reverberation?
Reverberation (or reverb) is the persistence of sound in a space after the original sound has stopped, caused by the sound bouncing off surfaces like walls, ceilings, and floors.
aids in localization
What does it mean by “reverb is less as sound source is approached”
people closest to the actual source of the sound would hear the more direct sound and not the reverb
What is a “reverb time”
the time for a sound to decrease to 1/1000th of original pressure
What happens if the revert time is too short, and if its too long?
Too short - music sounds dead and doesnt sound lively
Too long - music sounds muddy and mixed up
concert halls should have reverb time of 1.5-2.0 seconds
Bolt, Beranek, and Newman designed the Lincoln Centers Philharminic hall. They believed intimacy of sound depended on initial-time-delay-gap. Music sount terrible, why?
Seat-Dip effect = as sound passes over rows of seats, bass reveberation decreases as our bodies absorb it
Celiling panels were also too small and dispersed = absorbed too much low frequency sound
What is Primitive grouping?
Different sounds are grouped together for organization.
variables include: intensity, temporal change, location, timre, etc.
Eg, In a noisy restaurant, you can automatically group the waiter’s voice across background chatter
What is the difference between Temporal Segregation and Spectral Segregation
Temporal segregation = Sounds with similar timing patterns are grouped together. If they start and stop in sync or have a steady rhythm, your brain assumes they’re from the same source.
Spectral Segregation = Sounds with similar frequencies (pitches) are grouped together.If two sounds are very different in pitch, your brain may separate them into different “streams.”
What is Schema-driven Grouping
when your prior knowledge, expectations, and attention help you decide which sounds to focus on and group together. (top-down process)
