chapter 12 Flashcards
auditory space
perception of where sounds are located in space - auditory space extends around a listener’s head in all directions, existing wherever there is a sound
auditory localization
the locating of sound sources in auditory space
location cues
information created by the way sound interacts with the listener’s head and ears. the auditory information uses this information to determine location
what are the two types of location cues
binaural cues: depend on both ears
spectral cues: depend on just one ear
what are the three dimensions of sound position
azimuth: extends from left to right
elevation: extends up and down
distance: from the sound source to the listener (least accurate and works best when the sound source is familiar, or when cues are available from room reflections)
two types of binaural cues
interaural level difference and interaural time difference
interaural level difference
based on the difference in the sound pressure level of the sound reaching the two ears
acoustic shadow
the head acts as a barrier causing a difference in sound pressure level between the two ears, reducing the intensity of sounds that reach the far ear
when does the acoustic shadow occur
intensity is reduced in the far ear at high frequency sounds (greater than about 3000Hz for humans), but not for low frequency sounds
why does an interaural level difference occur for high frequencies but not for low frequencies?
because high frequency sounds have small spacing between them, meaning they are stopped by the head - whereas, low frequency sounds have large gaps in spacing, larger than the head, so are not affected
interaural time difference
the time difference between when a sound reaches the left ear and when it reaches the right ear
becomes larger as sound sources are located more to one side, and its magnitude can be used as a cue to determine a sound’s location
when is interaural time difference most effective
most effective at determining the locations of low frequency sounds
this makes it the dominant binaural cue because most sounds in the environment contain low frequency components
cone of confusion
an area extending from the ear that looks like a cone. sounds originating from different locations in this general area all have the same interaural level difference and interaural time difference, so location information provided by these cues is ambiguous
spectral cues
cues in which information for localization is contained in differences in the distribution of frequencies that reach each ear from different locations
caused by the fact that before the sound stimulus enters the auditory canal, it is reflected from the head and within the various folds of the pinnae
evidence for the pinae in determining elevation
when the inside contours of the pinnae are changed with a mold, localization for elevation coordinate is poor, but locations can still be judged along the azimuth coordinate
however, localization performance for elevation improves over time as people get used to the molds and is still good once molds come out (don’t have to readjust themselves)
jeffress model
proposes that neurons are wired so they each recieve signals from the two ears
coincidence detectors fire when signals from the left and right ears reach the neuron simultaneously - dif coincidence detectors fire to dif values of interaural time dif
itd is indicated by which itd neuron is firing
ITD Detectors
interaural time difference detectors - neurons in the jeffress model that fire when signals reach them from the left and right ears and are tuned to respond to a specific time delay between the two signals = information about possible locations of a sound source
ITD is indicated by which ITD neuron is firing
binaural localization in birds vs mammales
sharply tuned in birds: place code bc ITD id indicated by firing of neurons at a specific place in the nervous system
broadly tuned in mammals: population code bc ITD is determined by the firing of many broadly tuned neurons working together
superior olivary nucleus
first place that receives signals from the left and right ears
anterior vs posterior belt areas
two areas on either side of the auditory cortex
anterior: complex sounds/patterns of sounds - the what auditory pathway extends from the anterior belt to the front of the temporal lobe and then to the frontal cortex
posterior: localizing sounds - the where auditory pathway extends from the posterior belt to the parietal love and then to the frontal cortex
direct vs indirect sound
direct sound: sound that reaches your ears directly
indirect sound: reaches your ears after being reflected from a surface
precedence effect
when two identical or very similar sounds reach a listener’s ears separated by a time interval of less than about 50 to 100ms, the listener ears the first sound that reaches his or her ears
if the sounds are separated by a longer delay, they will hear two separate sounds
architectural acoustics
the study of how sounds are reflected in rooms - largely concerned with how indirect sound changes the quality of sounds we hear in rooms
reverberation time
the time it takes for the sound to decrease to 1/1000th of its original pressure
if reverberation time is too long: sounds become muddled because the reflected sounds persist for too long/echo
if reverberation time is too short: music sounds “dead” and it becomes more difficult to produce high intensity sounds
intimacy time
the time between when sound arrives directly from the stage and when the first reflection arrives - related to reverberation but involves just comparing the time between the direct sound and the first reflection, rather than the time it takes for many reflections to die down
bass ratio
the ratio of low frequencies to middle frequencies that are reflected from walls and other surfaces
spaciousness factor
the fraction of all the sound received by a listener that is indirect sound
auditory scene
the array of sound sources at different locations in the environment
auditory scene analysis
process by which the stimuli produced by each source are separated - hard when sounds from different sources are combined into a single acoustic signal
simultaneous grouping
the situation that occurs when sounds are perceptually grouped together because they occur simultaneously in time
sequential grouping
grouping that occurs as sounds follow one another in time
sequential grouping
grouping that occurs as sounds follow one another in time
how do we analyze simultaneous grouping?
- location
- onset synchrony (if two sounds start at slightly different times, it is likely that they came from different sources)
- timbre and pitch (sounds that have the same timbre or pitch range are often produced by the same source
- harmonicity ( when we hear a harmonic series we infer that it came from a single source because it is unlikely that several sound sources would create a fundamental and the pattern of harmonics associated with it)
how do we analyze sequential grouping
similarity in pitch (consecutive sounds produced by the same source usually are similar in pitch)
auditory continuity (sounds that stay constant or that change smoothly are often produced by the same source) - similar to gestalt principle of good continuation
experience (past experience)
auditory stream segregation
the effect that occurs when a series of sounds that differ in pitch or timbre are played so that the tones become perceptually separated into simultaneously occurring independent streams of sound
depends on pitch and the rate at which tones are presented
scale illusion/melodic channeling
when successive notes are a scale are presented alternately to the left and right ears smoothly ascending or descending scales are hears in ear ear even though each ear receives note
comes from grouping by similarity creating the illusion of smooth sequence of notes
multisensory interactions
use of a combination of senses - an example for vision and hearing is seeing a person’s lips move while listening to the person speak
ventriloquism effect/visual capture
example of vision dominating hearing - when sounds coming from one place appear to come from another place
two flash illusion
an illusion that occurs when one flash of light is presented, accompanied by two rapidly presented tones - presentation of the two tones causes the observer to perceive two flashes of light
another example of auditory visual interaction
speechreading
lip reading - lip movements provide information about what sounds are being produced
visual and hearing interactions in the brain
sensory areas in the brain are interconnected - high level of overlap between auditory and visual fields in the brain
echolocation
locating objects by listening to the echoes that bounce off them
echolocation can activate visual areas of the brain
