s&p exam 4 pt 2

Auditory localization

Dimensions

·      Dimensions: to figure out location

o   Azimuth: left right dimensions that goes all the way around your head

o   Elevation: Vertical / up and down dimensions that go all the way around your head

§  If you know the azimuth and the elevation it covers all directions

o   Distance: Knowing how far away something is

§  If you know all three of these dimensions then you can pick out exactly where a sound is coming from

Binaural cues

·      Binaural cues: use both ears at the same time and comparing the signal from one ear to the other

   Interaural time difference, Interaural level difference

·      Interaural time difference (ITD): Difference in timing that the sound is hitting each ear

·      Interaural level difference (ILD): The difference between the two sounds in the ear

o   Your head tends to absorb or reflect high frequencies

§  Treble

§  Doesn’t travel to the other side so the other ear can’t hear it

o   Your head tends to let lower frequencies pass through

§  Example: hearing loud music playing in the room upstairs - What’s making it down here are the bases /low sounds. Low frequencies are able to travel through your head

     Acoustic shadow, Cone of confusion

·      Acoustic shadow: Head is blocking area in space where the sound isn’t as loud / intense

·      Cone of confusion: Locations in space that lead to the same binaural cues

o   Going to get same time and level differences; binaural cues can’t tell the difference between sounds that are a little above or below one another

Solution to this- Spectral cues

§  The reason dogs tilt their head: angle ears to localize sound in space

§  Owls have upper and lower ears: Helps locate sounds in space better

Spectral cues

·      Spectral cues: direction of sound changes how its reflected in pinna

o   Folds in ear bounce sounds around in different ways depending on where the sound is coming from

o   Humans use as solution to cone of confusion

§  Have learned over life the different sound frequencies to know where in space the sound was coming from to know elevation.

·      Experient: Changes shape of ear but not blocking or clogging ear

o   Spectral cues were ruined; took away ability to perceive elevation

o   Got better over time when leaving mold in for a few weeks since you learn a new way to perceive sound in your specific ear

§  When they took out the mold the participant was still equally as good as it originally was before

Processing in the brain

     Brain structures

     Jeffress Coincidence Model

·      Jeffress coincidence model: two things meeting / coinciding each other

o   Neurons are receiving signals from both the left and right ears but those signals are coming from different directions.

o   To make them fire, they have to get two signals at once

o   Looking at when those two meet in the middle, then making the neuron fire, meaning the sounds are starting at the same time

§  The two sounds are not normally coming in at the same time

o   The signal / ear that starts earlier, makes a neuron fire that is more over on the opposite side from where the sound started

·      Place code: because the location of the neuron is related to the location of the sound

o   Evidence for this model comes from neurons in owls brain stems

§  Is what you would expect if the Jeff model was happening in their brain stems

o   Problem: Found in mammals compared to owls that the mammal responds better to sounds at different locations because mammals tuning curve is too wide

§  Cell in monkey auditory cortex, responding to sounds at different locations

o   In humans- If you look at the proportion at how strongly each are firing then compare the strength of them to figure out what’s going on

           Owls vs. Mammals

   Posterior vs. Anterior belt, What vs. Where pathways

                            Then hits the auditory cortex

·      A1: Localization cells

o   not great but can generally sense location

o   simple tones

·      posterior belt area: better tuned localization

o   neurons tuned to more places in space and can pick out exactly where a sound is coming from

·      anterior belt: even better at localizing different complex sounds

·      where pathway: information helps where sound is in space

·      what pathway: figuring out what the sound is

Sound in enclosed spaces

·      When you’re talking to someone, sound waves are going from you to their ear but also to the things around you

·      When in a room, some of the sound from voice is hitting the walls and are bouncing off and back to your ear

·      The same sound is hitting your ear over and over again because its coming from different directions

     Direct vs. Indirect sound

o   Direct sounds: hear these

o   Indirect sounds: there but you aren’t perceiving them

      Precedence effect

o   Precedence effect: always hearing multiple versions of the same sound but are only perceiving the first one / the direct sound, and that’s what you use to determine the location of the sound

  Performance halls – Reverberation time, Intimacy time, Spaciousness, Bass ratio

Acoustics

·      Reverberation time: the time it takes for the sound to die out

·      Intimacy time: lag between direct sound and first indirect sound

o   How long is the gap between ....

·      Spaciousness: fraction of all sound reaching the ear that is indirect

·      Base ratio: how the different frequencies are bouncing around

o   The ratio between how many low frequencies you’re getting vs how many high you’re getting

Auditory scene analysis

·      Separating different sound sources

·      Taking all soundwaves that are hitting your ear at once and splitting them up from the source its coming from

     Auditory stream segregation

·      Auditory stream segregation: grouping a series of sounds together

o   Techniques:

    Location, Onset time, Harmonicity, Timbre

Location

§ Interaural time difference (ITD)

§ Interaural level difference (ILD)

§ Spectral cues

Onset time

§ Notes were coming at two separate times from the trumpet and saxophone which helps you distinguish that they are coming from two different things, even when you can’t notice the location difference

Timbre

§ .....

Proximity & good continuation

§ Grouping things together because they’re close together

§ See something as two overlapping curve lines, not two v shapes

            Scale illusion

o   Scale illusion: grouping notes together based on proximity and good continuation

o   Auditory continuity: sound that is continuing in the background

§ Similar to vision where if you see something with something blocking it, you still perceive it as the same shape

o   Top down processing: prior experience are changing how you group sounds together

Multisensory interactions

·      vision and hearing are interacting and influencing the other

o   when sound is adding it gives you extra information

§ example: when two balls cross each other in an X with no sound compared to the same thing but with a clink sound it changes what you think you’re seeing to the two balls hitting in the middle and bouncing off each other

·      receptive fields

o   neuron responding to this same thing in space no matter if it is visual or auditory

      Echolocation

·      Echolocation: bats use it but humans can also learn how to use the techniques

Music perception

Purposes of music

·      Pitch

·      Melody

·      Timbre

·      Temporal structure

·      Harmony

o   Consonance & Dissonance

·      Emotional & physical response

Universal characteristics of music

·      Perceptual

o   Similar pitches are grouped together

o   Octaves are perceived as similar

·      Physiological

o   Music elicits emotions

o   People move with music

·      Social

o   Performed in social contexts

o   Caregivers sing to infants

Music & memory

    MEAMs (Music-evoked autobiographical memory)

Music-evoked autobiographical memory (MEAM)

Alzheimer patients vs. healthy controls

·      “recount in detail an event in your life”

Timing in music

·      Music: an art form and cultural activity whose medium is sound organized in time

o   Beat: Steady pulse of the music

o   Rhythm: Onset times of the notes

o   Meter: Repeating groupings of beats (in 2s, 3s, 4s, etc.)

    Beat, Rhythm, Meter, Syncopation

Beat

·      Basal ganglia

o   Greater activation for beats

o   Greater connectivity for beats

·      Premotor cortex

o   Strong activation for tapping

o   But also some just for listening

·      Brain waves

Rhythm

Syncopation

           Brain responses to beat

            Meter

              Accents; Interpretation – movement, vestibular stimulation, language

Meter

Accent

·    Duple meter

·    Triple meter

·    Don’t necessarily need accent

Movement

·    Even blindfolded

·    But NOT just watching

Melody

Melody: a series of tones that relate to each other

     Intervals, semitones

·      Intervals: the distance between two tones

o   Semitones:

o   Large intervals are rarer but are more likely to be up

o   Gap fill: Large intervals likely to be followed by motion in opposite direction

          Patterns in interval size, Phrases

      Tonality

·      Phrases: smaller series of notes

o   Likely to have longer pauses at the end

o   Likely to have larger interval after

o   Trajectories

·      Tonality: organizing notes around a key

o   How well do different notes fit into the key?