Hearin Aids
Transcript of Hearin Aids
-
8/8/2019 Hearin Aids
1/43
Not being able to see
isolates you from objects.
Not being able to hear
isolates you from people
Immanuel Kant
-
8/8/2019 Hearin Aids
2/43
H
E
A
R
I
N
G
AI
D
S
-
8/8/2019 Hearin Aids
3/43
RESIDUALHEARING
-
8/8/2019 Hearin Aids
4/43
Overview
HISTORY
TYPES
TECHNOLOGY PROGRAMMERS
SELECTION CRITERIA
-
8/8/2019 Hearin Aids
5/43
HISTORICAL PROSPECTIVE OF
HEARING AIDS .
-
8/8/2019 Hearin Aids
6/43
Hearing Aid Types
Body Aids
Behind-the-ear (BTE)
In-the-ear(ITE) In-the-canal(ITC)
Completely-in-canal(CIC)
-
8/8/2019 Hearin Aids
7/43
Body level BTE
IN THE EAR
HEAR
ING AIDS
INDIVIDUAL HEARING AIDS
-
8/8/2019 Hearin Aids
8/43
Technology
Analog
Digital
-
8/8/2019 Hearin Aids
9/43
Linear amplification
Oldest type of hearing aid amplification
Amplifies all inputs same amount
Does not address nonlinear nature of loudnessgrowth in SNHL
Uses peak clipping to prevent reaching LDL
Causes substantial distortion at high inputlevels
-
8/8/2019 Hearin Aids
10/43
Non-linear techonology:
Compression Threshold (CT)
Compression Ratio (CR)
CR= 2:1
For every 10 dB increase in input level, outputincreases by 5 dB
-
8/8/2019 Hearin Aids
11/43
Figure 3.2 Block diagram of an analog
hearing aid (top) and a digitally
programmable hearing aid (bottom).
Analog hearing aid
microphone receiverSignal path
Programmable hearing aid
Signal
path
Digital
controller and
memory
programmer
unit
programmer
interface
Source: Dillon (2001):
Hearing Aids
Analog and
digitally-programmable
block diagrams
-
8/8/2019 Hearin Aids
12/43
Compression limiting versus peak clipping
Peak clipping: chops the tops off
sounds
Compression limiting: rapidly turns
the volume down
To prevent excessive loudness:
-
8/8/2019 Hearin Aids
13/43
Compression
Control of hearing aid output to within
dynamic range
Weak intensity inputs are amplified more thanhigh intensity
Nonlinear relationship
Cuts down on distortion and uncomfortableoutput levels
-
8/8/2019 Hearin Aids
14/43
Peak clipping versus compression limiting
Original Clipped Compressed
-
8/8/2019 Hearin Aids
15/43
Compression
0
20
40
60
80
100
quiet loud
Amount of Noise
Amplific
ation
ReducesAmplificaton
when its Noisy.
Helps you hear more
when its Quieter.Keeps it from being
Painful when its Noisy
Adjustable (manual and
automatic).Different settings in
multiple frequency bands.
-
8/8/2019 Hearin Aids
16/43
Channel versus Band
In a channel, can change gain, CR, CT, etc.
Band typically refers to ability to change gain only
Can have multiple bands in one channel
Example:In a particular hearing aid, channel onegoes from 250 to 1500 Hz. There are three bandswithin the channel centered at 500, 750, and 1000 Hz.
-
8/8/2019 Hearin Aids
17/43
Changing the CRorCRin channel one will
affect all frequencies from 250 to 1500 Hz.
Also would have the flexibility to adjust the
gain independently using the three bands (at500, 750, and 1000 Hz) within channel 1
-
8/8/2019 Hearin Aids
18/43
Microphones
Directional versus omnidirectional
Using Directional can be helpful in noisy
situations. The best hearing aids can switch between the
two.
-
8/8/2019 Hearin Aids
19/43
-
8/8/2019 Hearin Aids
20/43
Telecoil
Converts magnetic energy to electrical signal
Telecoil option only available on certain styles
Telecoil automatically activated or manual
Push button .
-
8/8/2019 Hearin Aids
21/43
Advantages
FeedbackManagement
Noise Management
Automatic adjustment between programs
-
8/8/2019 Hearin Aids
22/43
Programming Hardware and Software
Hi-Pro Box Hearing Instrument Programmer
Interface between computer/fitting software and the
hearing aid Can be a standalone unit or built within the probe mic.
system
NOAH Software platform that facilitates data storage and
transfer Information such as audiometric data can be used with
any manufacturer that has adopted this standard
-
8/8/2019 Hearin Aids
23/43
NATIONALACOUSTICLABORATORIES NON LINEAR
PROCEDURE (AUSTRALIA)
NAL NL
-
8/8/2019 Hearin Aids
24/43
Hi pro
-
8/8/2019 Hearin Aids
25/43
NOAHlinks wireless Bluetooth connection
allows for
easy fittings up to 16 feet away from yourcomputer
without the hassle of programming cables
-
8/8/2019 Hearin Aids
26/43
Noah link
-
8/8/2019 Hearin Aids
27/43
-
8/8/2019 Hearin Aids
28/43
Dynamic Range
Range in dB between threshold and loudness
discomfort level
With normal hearing, speech sounds fallwithin the dynamic range
-
8/8/2019 Hearin Aids
29/43
Wide dynamic range compression
Moderate
Weak
Intense
NormalImpaired
-
8/8/2019 Hearin Aids
30/43
-
8/8/2019 Hearin Aids
31/43
Conductive Hearing Loss
Loss of sensitivity for all sounds
No reduction in dynamic range
Need gain, once sounds are audible should do well
-
8/8/2019 Hearin Aids
32/43
Sensorineural Hearing Loss
Loss of sensitivity for low-mid intensity sounds
Complete or partial recruitment
Reduction in dynamic range
Deficits in Frequency and temporal resolution
Need increased audibility and improved SNR to
function at normal levels
-
8/8/2019 Hearin Aids
33/43
Sensorineural Hearing Loss
Normal Hearing
Uncomfortably Loud 100 dB 100 dB
5 dB
Loud, But OK 0 dB
7 dB
Comfortably, but 0 dB
Slightly Loud 7 dB
Comfortable 5 dB 57 dB
Comfortably, 0 dB dB
But slightly soft
0 dB
Soft 25 dB
ery Soft 10 dB
Dynamic Range = 100-10 = 0 dB 100- 0 = 70 dB
Indicates need for Non-linear processing
-
8/8/2019 Hearin Aids
34/43
WHAT IS SPEECH BANANA?
It has been found that when speech is presentedfrom about 1mt distance at a conversational
level, each speech sound has a different
intensity and frequency pattern though the
overall intensity of speech is 0- 5dBSPL.
The speech sounds lie in a sort of cluster. If the
border of this cluster are defined, a shape not
unlike a banana emerges. This is called as
speech banana.
-
8/8/2019 Hearin Aids
35/43
-
8/8/2019 Hearin Aids
36/43
-
8/8/2019 Hearin Aids
37/43
USES OF SPEECH BANANA
speech banana is very useful for hearing aid
fitting.
Speech banana is useful for the selection of
hearing aid.
It is very important in interpreting aidedaudiogram.
Speech banana shows acoustic
characteristics of different sounds that isconsonants and vowels in the language.
It is useful for parental counseling.
-
8/8/2019 Hearin Aids
38/43
Single versus Multichannel
With sloping hearing loss, single channelcompression may lead to inappropriate degreeof compression in certain frequency regions.
Most advanced circuits are multichannel.
Most individuals will benefit from multiple
channels because different compression valuesare needed in different frequency regions
-
8/8/2019 Hearin Aids
39/43
Button, switch, or Remote
Hearing aid need the capability to automaticallyswitch between memories depending onenvironment.
Depending on number of options, may have oneswitch, one memory button, or both.
Need to consider dexterity and cognitive functioning
of patient.
-
8/8/2019 Hearin Aids
40/43
Main contributors to earmold acoustics:
Venting
Dampers
Soundbore/horn effect
-
8/8/2019 Hearin Aids
41/43
Styles
Standard: Shell Half Shell
Skeleton Semi Skeleton
Semi Canal
Canal Tip
-
8/8/2019 Hearin Aids
42/43
BinauralAdvantage I
Improved signal clarity in many
contexts due to combination of
Binaural summation
Binaural interaction (squelch)
Minimize the Head shadow effect
-
8/8/2019 Hearin Aids
43/43