Perception 5 Flashcards
How is sound localised?
Based on both binaural cues and monaural cues
What are the difference between these two cues?
Binaural = requires both ears and is important for location of sound in azimuth
-ITD’s
-ILD’s
Monaural = requires only one ear and helps in elevation and distance of sound
Describe ITD’s
Interaural time differences
Amount of time that it takes for sound to reach both ears relies on azimuth location
If the sound is straight ahead then sound reaches both ears at the same time, if the sound is more to one side then one ear receives it before the other
Can differ due to speed of sound and distance between both ears
Describe ILD’s
Interaural level differences
An acoustic shadow can be created by the head, which can result in one ear hearing sound louder than the other ear
Most noticeable for high frequency sounds e.g. 6000Hz
How do these processes occur?
Binaural processing
D
Describe binaural processing
Binaural localisation cues can be found in different types of superior olive (located in brain stem)
Lateral superior olive contains ILD sensitive neurons
Medial superior olive contains ITD sensitive neurons
State the strength and weakness of this process
Strength - help to give information about where the azimuth is located e.g. the ITDs tend to work well for low frequency sounds
Weakness - lacks to tell us much about difference and creates a cone of confusion (set of points where the sound source creates identical ITDs and ILDs
Describe the monaural localisation cues
Sound hits off pinnae and the intensity of sound frequencies tend to change
Sound intensity lowers the further away it is, and so if it’s closer the amplitude will be high
People have different ear shapes and so everyone experiences complex sounds differently
Reverberation is when reflections come together to create a persistent sound and this can cause precedence effect (sound followed by another sound, echoes)
What is spectral grouping?
Linked to auditory scene analysis
Treating different frequency sounds as belonging to the same sound source
Harmonicity can occur where one component of sound is mistuned and then it appears to be a separate sound
Principle of common fate can occur
What is sequential grouping?
Combining sequences of sound over time known as auditory stream segregation; how you organise sounds into separate perceptual events
Linked to ambiguous figures and sounds
What factors can affect grouping sequences of sound?
-Similarity of pitch
-Temporal proximity
-Continuity
-Similarity of timbre
Similarity of pitch is…
Sounds of similar pitch tend to be created by the same source
Temporal proximity is…
Sounds that occur in rapid progression are created by the same source
Continuity is…
Sounds that either stay constant or change smoothly tend to be created from the same source, they are perceived as continuous sounds despite there being an interruption
