Music Perception Flashcards
What are the goals of cochlear implants?
- Detection of environmental speech
- Speech understanding (in quiet*; in noise?)
- Music?
- IMPROVED QOL**
What technological factors contribute to difficulties in music perception with a CI?
- Music is more complex in terms of spectral, temporal, and timbral aspects (as well as DR)
- Pitch is most severely degraded due to reliance on place (spectral) and temporal cues
- 22 physical elements need to compensate for functional loss of 3500 IHCs
- Incoming signal is BPF for speech signals (~250-8000 Hz)
- Spectral spread from electrical fields leads to further degradation
What surgical/anatomical factors contribute to difficulties in music perception with a CI?
- Further reduces spatial sensitivity
- Electrode proximity to nerve fibers
- Less-than-ideal electrode placement
- Cochlear abnormalities
How high is rate-pitch info in NH? CI?
- For NH, synchronized nerve firing produces rate-pitch info up to 5000 Hz, whereas CIs saturate at 300 Hz
- Increased rates needed to represent rate-pitch info above 300 Hz lead to channel interaction
- CI users also have trouble perceptually integrating rate cues with changes in signal envelope
What biological factors contribute to difficulties in music perception with a CI?
- Loss of peripheral nerve fibers/cell bodies = lead to the need for increased current levels, spread of excitation (loss of specificity)
- Loss of myelination = prolonged latencies, altered refractory periods, reduced temporal resolution, diminished neural efficacy (greater power consumption)
- Unclear how many remaining nerve fibers are needed for music appreciation
- Synaptic loss and increased response latencies in the CN and IC further decrease temporal resolution
What acoustical factors contribute to difficulties in music perception with a CI?
- Rhythm
- Tempo
- Melody
- Timbre
What is rhythm?
- Series of beats and rests that produce patterns over time
- Independent of tempo (speed) of music
- Temporal gaps and amp modulated pulse trains encode rhythmic patterns
- CI users do well with rhythm, regardless of type of music (similar to NH)
What is tempo?
- Speed or rate (beats per minute)
- Creates the effective mood of the piece
- Remains relatively intact for CI users
- Discrimination is ~4-6 bpm
What is melody?
- Sequential series of pitches that create the musical phase
- Accuracy for closed set discrimination ranges from 0 to 95% correct (for familiar melodies or real world songs)
- Generally much worse than NH controls
What is timbre?
- The feature that distinguishes 2 notes of the same pitch, loudness, and duration; “tone quality”
- Discriminating between 2 instruments
- Wide range of performance for CI users on identification task, but consistently
- Utilizes envelope and fine structure cues (NH uses both, but CI relies solely on envelope)
Is music presented as fundamental components or streams?
- Streams
- Auditory stream segregation allows us to process complex signals
- Perceptually similar sounds are grouped into a single stream
- Separate melody from background accompaniment
- CI listeners are largely effected by competing instruments for timbre and melody tasks
- Fusion vs. fission
What is fusion?
-Envelopes are similar so hear one continuous strand of music
What is fission?
-Envelopes are different enough to distinguish, can hear multiple streams of music
How do we improve music perception for CI users?
- Music rehab may improve melodic contour and timbre identification w/ subjective improvements in appraisal (degree of improvement related to amount of training)
- Music appraisal ratings and perception abilities do not generally improve with incidental exposure like speech perception does
- Melody training significantly improves abilities (similar in adults and peds)
- However, limited music rehab programs exist
What are the proposed theories of pitch perception?
- Temporal theory
- Tonotopic theory
- Combo
