m usic through a cochlear implant Dr Rachel van Besouw Hearing amp Balance Centre ISVR What a cochlear implant CI is and who can have one What a CI sound processor does How CI hearing compares to normal hearing ID: 467398
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Slide1
More From Music
m
usic through a cochlear implant
Dr Rachel van Besouw
Hearing & Balance Centre, ISVRSlide2
What a cochlear implant (CI) is and who can have one
What a CI sound processor doesHow CI hearing compares to normal hearing
Why music is particularly challenging for CI usersHow to get More From Music…
What will I learn in the next 25 minutes?Slide3
A CI is a surgically implanted device that electrically stimulates the auditory nerve fibres in the inner ear
Image courtesy of AB
What is a CI?Slide4
Ear canal
Pinna
Ear drum
Ossicles
(hammer, anvil & stirrup)
Image courtesy of AB
Cochlea
Auditory nerve
What is a CI?Slide5
Microphone(s)
Sound processor
Transmitter coil
Receiver coil & stimulator
Electrode array
Image courtesy of AB
What is a CI?Slide6
People with severe-to-profound
hearing loss in both ears
Due to abnormalities in the cochlea
Image courtesy of AB
Cochlea
Who is it for?Slide7
Aging
NoiseCertain medicines
Viral and bacterial infection (rubella, measles, meningitis) Ménière’s
diseaseGenetic origin
Premature birth
Head injury
Abnormal cochleae
Micrographs:
Keithley
, E.M. in: Ryan, A.F.
PNAS
2000;97:6939-6940
What causes this type of hearing loss?Slide8
What a cochlear implant (CI) is and who can have one
What a CI sound processor doesHow CI hearing compares to normal hearing
Why music is particularly challenging for CI usersHow to get More From Music…
What will I learn in the next 25 minutes?Slide9
What does a CI sound processor do?
microphone(s)
sound processor
transmitter coilSlide10
Sound processing stages
Pre-emphasis
(boosts frequencies important for speech
)
Automatic
gain control
(compresses the loudness range
)
Speech
enhancement
(reduces unwanted background noise)Slide11
Sound processing stages
Splits the sound signal into frequency bands
(the number of bands depends on the number of available electrodes)Slide12
Sound processing stages
Generates the pulse sequences for each electrodeSlide13
Sound processing stages
Sets the amplitude range for each electrode
(ensures that the amplitudes of the pulses are above threshold, but below the most comfortable loudness level)Slide14
Sound processing stages
Turns the data into a radio frequency (RF) signal for transmission to the implant Slide15
What a cochlear implant (CI) is and who can have oneWhat a CI sound processor
doesHow CI hearing compares to normal hearing
Why music is particularly challenging for CI usersHow to get More From Music…
What will I learn in the next 25 minutes?Slide16
decibels
120
110
100
90
80
70
60
50
40
30
20
10
0
-10
Loudness & Dynamic Range
loud
soft
How does a CI compare to normal hearing?Slide17
decibels
120
110
100
90
80
70
60
50
40
30
20
10
0
-10
Loudness & Dynamic Range
loud
soft
~20 dB range
How does a CI compare to normal hearing?Slide18
Pitch
How does a CI compare to normal hearing?Slide19
l
ow pitch region in cochlea
l
ow pitch info
high pitch info
high pitch region in cochlea
CI input
CI output
Pitch
How does a CI compare to normal hearing?Slide20
What a cochlear implant (CI) is and who can have one
What a CI sound processor doesHow CI hearing compares to normal hearing
Why music is particularly challenging for CI usersHow to get More From Music…
What will I learn in the next 25 minutes?Slide21
A visual analogy…
Why is music particularly challenging?
Image courtesy of Alan
OlleySlide22
Over the Rainbow
(Piano Only)
Some
where over the rainbow way up high
…
time
amplitude
Music…Slide23
Over the Rainbow
(Piano Only)
Some where over
the
rainbow way up high
…
frequency
(high
)
(low)
…is complexSlide24
Over the Rainbow
(Piano Only)
Over the Rainbow
(Piano Only)
Some where over
the
rainbow way up high
…
Filtered into >= 22 channels…
frequency
(high
)
(low)Slide25
… and turned into pulse sequences
Some where
ov
-
er
the rain-bow way up high…
Over the Rainbow
(Piano Only)Slide26
The normal cochlea has ~16,000 hair cells and many more nerve fibres, which provide fine pitch cues at different locations
Cochlear implants have between 12 and 22 electrodes and these can produce different pitches depending on their location
(the further into the cochlea, the lower the pitch)Some electrodes may sound the same, resulting in even fewer place pitch cues
Limited ‘place cues’ for pitchSlide27
The rate of the pulses delivered by the electrodes is
fixed and is usually too high to provide timing or ‘temporal’ cues about pitch
Temporal pitch cues from the envelope of the pulse sequences are there, but they are weak.Limited ‘temporal cues’ for pitchSlide28
More electrodes will not necessarily
result in better pitch perception due to:
current spread (each electrode affects a large area)the condition of the cochlea
(auditory nerve fibres may have degenerated)
What if we used more electrodes?Slide29
What a cochlear implant (CI) is and who can have one
What a CI sound processor doesHow CI hearing compares to normal hearing
Why music is particularly challenging for CI usersHow to get More From Music…
What will I learn in the next 25 minutes?Slide30
Whilst it is true that pitch is important for melody, melody is not essential
for musicRhythm is conveyed very well by the implant
Loudness cues (although compressed) can convey the dynamics of musicGross changes in the frequency spectrum are also conveyed by the implantMusic ≠ MelodySlide31
Music with clear changes in pitch
Music with a clear rhythm
Music will a simple arrangement
Appropriate volume
Quiet listening environment or direct input (TV/Hifi audio cable)
Clues for interpreting music (visual aids, lyrics
etc
)
Training & repetition…
?
What can help?Slide32
Interactive music awareness programme
24
x 30 min structured sessions Interactive software applications enabling users to manipulate music to suit their implant
Uses subtitled
video tutorials and written instructions
To be launched free online with a user forum ~Jan 2014 @
www.MoreFromMusic.orgSlide33
More From Music
Email us for further information…
Rachel:
rvb@isvr.soton.ac.uk
(project info, research collaboration)
Ben:
b.oliver@soton.ac.uk
(compositions, stems, software
)
Sarah:
s.m.hodkinson@soton.ac.uk
(professionals’ training)
Mary:
mlf@isvr.soton.ac.uk
(workshops for patients)o
r visit the music focus group websitewww.soton.ac.uk/mfg