What is SRT?
Speech Recognition Thresholds
lowest presentation level for spondee words at which 50% can be identified correctly.
What's a spondee?
a word with equal stress on each syllable
i.e. airplane, baseball, toothbrush
How is a spondee test given to a young child who cannot read?
examiner asks child to point to words when examiner says the word
What are speech discrimination scores?
percentage of monosyllabic words presented at a comfortable listening level that can be correctly repeated by the pt
What are speech discrimination scores useful for?
What should the score be to be a candidate for hearing aids?
above 50%, if a pt. has less than this, they should NOT be fitted for hearing aids
What is involved in the hearing aid fitting process?
Fitting and Verification
Evaluation of Aided Performance
What are the components of the hearing aid?
Volume control (not on all HAs)
On/Off switch (sometimes joined with volume control)
Dispenser-adjusted potentiometers - changes sound of hearing aid. Add treble, bass. In older types of hearing aids.
Telephone/Telecoil switch (see article)
What are the 5 eras of history of hearing aids?
acoustic - 1600s
Who was the first to receive a hearing aid?
Queen Alexandra got the first hearing aid in 1902, Acousticon hearing aid
She had osclerosis from having six kids, her hearing got worse and worse.
When was the carbon era and what was it?
1899 First wearable model
The carbon microphone contained carbon dust . The movement of the microphone diaphragm depended on the movement of the carbon dust. A small volt battery and magnetic receiver were also part of the HA
What improvement did the carbon hearing aid provide?
What year was the vacuum era and what was it?
Practical during 1930's
Used vacuum tubes together to create very powerful amplifiers
Very large to wear- as large as an end table or as small as a suit case
What improvement did the vacuum hearing aid provide and who was it mostly used for?
severe to profound hearing loss
When was the transistor era and what was it?
Reduction in battery size
First head-mounted hearing aids introduced as part of eye-glasses.
What are the primary styles of hearing aids?
1950's: Body Aids (BA)
1960's: Behind-the-ear (BTE)
1960's: Eyeglass (EG)
1970's: In-the-ear (ITE)
1980's: In-the-canal (ITC)
1990's: Completely-in-the-canal (CIC)
In 1960, what was the technology for the BTE hearing aid?
Integrated circuit applied
Multiple components (transistors, resistors) were combined into a single component, thus enabling HAs to get smaller and smaller
When did digital processing begin and who started it?
1960s with Bell Laboratories
When was the first commercial hearing aid introduced?
What are the 4 advantages of body aids?
1) Larger controls are helpful for elderly who have dexterity and vision problems
2) Less expensive for developing countries
3) Utilizes cheaper batteries, AA size
4) Some use solar power energy and last up to 2 weeks without recharging
What are the 6 advantages of the BTE hearing aids?
1) Less expensive
2) no special modifications and can be manufactured in advance of a placed order (Can have same-day fitting with temp earmold)
3) most powerful hearing aid style in terms of gain and output
4) compatible with many assisstive listening devices
5) larger battery provides longer operating life
6) larger use controls for elderly to handle
What is the most appropriate fitting hearing aid for children and why?
BTE because only the earmold needs to be changed as the child grows
What is the premiere choice hearing aid for severe to profound hearing losses?
BTE, because of the significant gain and output
What are the 2 advantages of the ITE (In-the-ear) hearing aid?
1) smaller styles are easier are easier to insert and remove
2) smaller are styles are less susceptible to wind noise
What are the 2 advantages of CIC hearing aids?
1) small size
2) microphone placement - natural sound, hearing aid is closer to tympanic membrane to block out background noise.
What are the disadvantages of the CIC?
1) small size makes it difficult for elderly to change battery
2) lack of directional microphone
3) More frequent repair
4) more susceptible to perspiration and wax build up
5) volume control is not available
What is an ITD hearing aid?
In the drawer, since 15% end up unused
What are the 5 most cited reasons for dissatisfaction with hearing aids?
1) poor perceived benefit
2) inability to hear in background noise
3) poor fit/comfort
4) negative side effects
5) price/cost of repairs
What are the different hearing aid technologies?
Linear - amplification goes in and out of hearing aid
Analog with improved technology
Programmable-digital (entry-level digital)
True digital/Most advanced digital
What is linear technology?
Same amount of amplification for all levels of input. Least sophisticated. Frequency shaping is none to limited.
What is peak clipping?
- occurs in linear hearing aid
- amplitude of audio signal is beyond limits of amplifier or receiver
- increase in distortion
What are POTENTIOMETERS (POTS)?
Tone (low cut, high cut, peak shift)
Output limiting (AGC-O, MPO)
Input limiting (AGC-I)
What are compression circuits?
handles loudness tolerance problems without distortion
What are compression limiting circuits?
linear amplification for low intensity sounds.
Once the incoming sound reaches a predetermined intensity level, called the 'kneepoint', the gain is reduced
What does compression do?
Gain stays below saturation point bc if not there will be distortion
What are the automatic signal processing circuits?
BILL and TILL
Bass and Treble are adjusted in response to input levels
What is K-AMP?
takes narrow dynamic range and opens it up
What is WDRC?
Analog technology WDRC-wide dynamic range compression adds all sounds to be in comfortable zone.
attempting to put all speech sounds at individual's 'comfort zone'
What is expansion?
Analog technology—reduce unwanted continuous 'soft' background noises (like the humming of a fan or computer noise)
What are the benefits of programmable hearing aids?
1) advanced signal processing (gain) - softer sounds are amplified more than louder sounds based on the sound reaching the microphone
2) Compression- constantly adjusts gain, so softer sounds can be heard and loudness level (kneepoint) to adjust
3) Multi-channel Frequency
4) Multi-memory capability
5) Multi-microphone capability
What is the difference in advanced signal processing and traditional hearing aids?
Advanced signal processing automatically adjusts amount of amplification (gain), based on what hits the microphone
Traditional linear hearing aids have a set amount of gain, regardless of the loudness reaching the microphone.
What is compression?
hearing constantly adjust the amount of gain, so softer sounds are amplified and louder sounds are more comfortable
What is recruitment?
loudness discomfort at softer than normal noise levels
How often should hearing aids be purchased?
every 5 years
What is frequency response?
amount of gain a hearing aid provides at each pitch or frequency
What is multichannel frequency?
dividing frequency response into 2 or more channels of control
allows hearing aid to respond differently to high pitched and low pitched sounds
What is multi-memory capability?
ability to store multiple frequency responses or programs. (may include meetings, restaurant)
can be controlled using remote control
audiologist and pt. decide which programs to set
Who can benefit from multi-memory capability?
those who communicate in many different listening situations
or who have fluctuating hearing loss
What is multi-microphone capability?
one microphone picks up sound from broad area
other microphone picks up sound from a narrower range
hearing aid user can choose which microphone to use depending on situation
What are the costs for programmable hearing aids?
4X costs of traditional hearing aids
What is the difference between artificial intelligence hearing aids and digital hearing aids?
AI continuously adjusts to changing sound environments
AI is real-time with parallel signal processing
Digital has serial signal processing
What are specialty hearing aids?
What are CROS hearing aids?
Contralateral Routing of Signal
unaidable hearing loss in one ear
normal hearing or aidable in the other ear
- good hearing in one ear and the opposite ear cannot benefit from amplification
What are BICROS hearing aids?
Bilateral Contralateral Routing of Signal
one ear is unaidable
some degree of aidable hearing loss in other ear
- 2 microphones: one near the better ear and the other near the poorer ear
-signals are delivered to one receiver, output goes to best ear.
What are multicros hearing aids?
Client-operated switch, he/she can switch between CROS, BiCROS or Monaural.
What are transcranial cros hearing aids?
Powerful hearing aid worn deep in the canal of the "bad" ear (when person has less than 50%)
How does the transcranial or bone conduction hearing aid work?
The sound travels to the "good" ear via bone conduction
a vibrator is placed behind the ear and over the mastoid bone
Who are bone conduction hearing aids for?
those who have congenital atresia (missing or incomplete ear canals)
For use with medical untreatable conductive hearing losses
chronic infection of the middle or outer ear
middle ear damage
What are the disadvantages of a traditional bone conduction hearing aid?
Cumbersome and uncomfortable
High frequency attenuation as sound passes through skin
Who is BAHA (bone anchored hearing aid) for?
For patients with unilateral sensorineural hearing loss, also known as single sided deafness (SSD)-- as an alternative to using CROS
conductive and mixed hearing losses
Have to have a good ear
What is the difference between BAHA (bone anchored) and bone conduction?
Similar to bone conduction but it is more comfortable, less cumbersome
Some studies report better word discrimination/word identification with BAHA as compared to traditional bone conduction.
What is MEI and who uses it?
Middle Ear Implant
for conductive and sensorineural losses
Where is a MEI placed and how does it work?
Middle ear crystal
Stimulate middle ear through mechanical vibrations of piezoelectric and electromagnetic delivered to the ossicles
What is a reason patient may be dissatisfied with their voice?
Why would a person get a MEI?
For patients dissatisfied with own voice
Past discomfort with traditional Has
Multiple HA repairs
Multiple office visit
Sensitive ear canal
Exostosis- bony growths block sound, swimmer's ear
What are the advantages of MEI?
Theoretically can improve high frequency signal -no insertion loss.
Reduction in acoustic feedback
No occlusion effect
Who is a candidate for MEI?
Over 18 yrs of age
Moderate to severe SNHL
Patients having had experience with traditional HA desiring alternate devices/solutions
Speech identification scores at least 50%
Medically approved middle ear function
How does a MEI work?
In summary, Microphone—electric charge—crystal bends—causes bones to vibrate—transduce sound
Two options: own eardrum acts as microphone or an actual small mic is inserted in the ear canal wall
What are the 2 methods of transduction for MEIs?
How does piezoelectric method of MEIs work?
when placed in the bones of the middle ear the crystal flexes and bends as a small electric current flows from the microphone
How does electromagnetic method of MEIs work?
Similar process to the crystal but instead of using a crystal the microphones communicates with a coil of wire (within the ME bones) creating a magnetic field. The ME bones vibrate in synchrony with the magnetic field
What is the major advantage of piezoelectric implementation over electromagnetic implementation?
Who are disposable hearing aids for?
Used for patients who do not yet 'own' their hearing problem, that is, used as starter HA.
Or for those not willing to commit to a 'real' hearing aid (younger adults).
What are the advantages of disposable hearing aids?
Good to get people to accept their hearing loss initially
What are the disadvantages of disposable hearing aids?
- Not custom made, may not fit well
- Amount of money you spend monthly is cost of buying over 6 years
- Can take 1-3 months to get used to hearing aid technology
What are the 5 advantages of binaural amplification
1) Eliminate head shadow
2) binaural squelch (improved hearing in noise)
3) localization is improved
4) Loudness summation (3dB better with binaural amplification, can be up to 6dB)
5) Wide dynamic range
What are the 4 monaural advantages?
1) Unaidable ear
2) Physical limitations of user
3) User preference
4) Poorer speech discrimination binaurally than monaurally - may have poor fusion, therefore just amplify one ear
What is an earmold?
couples the hearing aid to the user's ear via a tube
What are the acoustic effects of earmolds and hearing aid shells?
can be modified to amplify signal by:
- TUBE DIAMETER
- TUBE LENGTH
- LENGTH OF EARMOLD CANAL
- BORE DIAMETER AND LENGTH
- OPEN VS. NON-OCCLUDING
- FILTERS (NOT REALLY USED ANYMORE)
How can low frequencies be modified?
drill small hole into the canal of earmold
How does venting effect low frequencies?
larger the vent, the more low frequency reduction (attenuation)
AKA Open fitting
What are 3 primary reasons earmolds are vented?
1) allow unwanted amplified low frequencies to escape from the ear canal
2) release pressure to avoid a plugged ear sensation
3) allow normal input of unamplified sound
How can you modify mid-frequency?
What do acoustic dampers do?
placed within tubing
Smooth out peaks of the frequency response
How can high frequencies be modified?
increasing the internal diameter (2mm-4mm)
What does increasing the diameter do?
An acoustic horn will crease gain in the 3000-4000 Hz region, where many of the speech sounds are
What is used to measure real-ear output?
AKA 'real ear', or in-situ measurement
The greater the hearing loss, the more....
closed the vent needs to be
What are the standards electroacoustic performance characteristics of hearing aids?
American National Standards Institute
ran by volunteers
What tool measures the output of a hearing aid i.e. electoanalysis?
microphone known as a 2cc coupler
2 cubic centimeters
2 styles: HA-1 or HA-2
What 6 items are assessed when conducting an electroacoustic analysis?
1) Output Sound Pressure level
2) High frequency range (GAIN)
3) High frequency average full-on Gain (Gain and volume turned at loudest level)
4) Frequency Range
5) Total Harmonic Distortion
6) Equivalent Input Noise
How can you verify hearing aids subjectively?
Functional gain--aided vs. unaided sound field measures of hearing levels for tones and speech (with & w/out haids inside booth)
How can you verify hearing aids objectively?
Aided vs. unaided real-ear measures of gain and output using probe microphone in ear canal.
What are the 3 most important factors to consider when qualifying a person for a hearing aid?
1) Degree of hearing loss
2) Amount of communication skills
3) Motivation to use hearing aids
What qualifies a person for hearing aids?
1) if speech frequencies of 3000-4000 Hz are affected
2) Below 85% on the Audibility Index
What are the 3 preselection measurements for pretesting a candidate for hearing aids?
1) Pure tone thresholds
2) LDL (loudness discomfort level)
3) Speech in noise testing
What do pure tone thresholds measure?
- used to calculate the hearing aid gain requirements and predict LDLs
- used to determine if there is a conductive component to the hearing loss
What are the important aspects in hearing aid selection?
1) hearing aid style
2) Gain and frequency response
3) multiple channels (signal processing through frequency range)
4) multiple memories (different listening environments)
7) Directional technology
8) bilateral fittings
What is gain and frequency response?
Gain is calculated using the person's thresholds and LDL
What is the audiogram interpreted in?
HL - hearing level
What do manufacturers and audiologist program and speak in?
SPL- sound pressure level
A hearing aid is ________ by the audiologist
A cochlear implant is _________ by the audiologist
What is compression?
WDRC - wide dynamic range compression allows hearing to be within the dynamic range
What is dynamic range?
the difference between a listener's LDL and threshold signal (either PTA or speech)
What is expansion?
compresses signals below the kneepoint and allows pt. to use the gain necessary to make soft speech audible without negative side effects of ambient noise
What is the most effective method to improve signal to noise ratio?
directional microphone technology
What is the improvement of directional hearing aids?
- can improve speech understanding by 50%
What does probe-tube microphone measure?
objective measurement of unique acoustic properties of the ear and earmold coupling
What is REUR?
- real ear unaided response (REUR) is the SPL, as a function of frequency, at a specified point in the unoccluded ear canal, for a specified soundfield.
- demonstrates individual's ear canal resonances.
- Can serve as indicator of abnormalities of the ear canal
What is REOR?
- real ear occluded response (REOR) is the SPL, as a function of frequency, at a specified point in the ear canal, for a specified soundfield,
- with the hearing aid in place and turned off
What is REOR used for?
- to determine venting characteristics
- Determine individual's loss of 'natural ear-canal resonances'
What is REAR?
real ear aided response (REAR) is the SPL, as a function of frequency, at a specified measurement point in the ear canal, for a specified soundfield
- with the hearing aid in place and turned on
What does REAR + REUR= ?
REIR Real Ear Insertion Response
difference, in decibels as a function of frequency, between the REUR and the REAR measurements taken at the same measurement point in the same soundfield
What is the purpose of REIR?
- To determine whether a particular hearing instrument setting has achieved a particular insertion gain prescriptive target (e.g., NAL_R, DSL, FIG 6.)
- Without a prescribed target, REIG becomes meaningless
What is REIG?
- real ear insertion gain
- value in decibels of the REIR at a specific frequency
- used to customize 2cc cupler
What 3 things are verified with a hearing aid prescription?
1) Correct Gain
2) Frequency Response
3) Signal processing characteristics
How is prescription verified?
1) informal rating of speech quality and intelligibility
2) speech recognition or intelligibility (HINT and QUICKSIN tests)
3) Loudness Scaling
4) Probe-microphone measurements
How is loudness scaling tested?
present connected speech at 45dB SPL, 65 dB SPL, and 85 dB SPL
make adjustments as necessary to gain, compression, and/or output
What do we look at when selecting amplification for a person?
2) Ear size, anatomical structures
3) Lifestyle needs
4) Family considerations
5) Adult or child
6) commitment to better hearing
What are ALDs?
Assistive Listening Devices
What are the 2 most common ALDs?
Sound Field Systems
How do ALDs help? 3 ways
1) They cut down on background noise.
2) They make faraway sounds seem closer to the child.
3) They help the child hear in a large room, like an auditorium.
What are the benefits of an FM system?
easy to operate
can be used indoors and outdoors
can be simultaneously in adjacent rooms
electromagnetic interference is not a problem
doesn't require receiver be in direct line of sight with receiver
What is the limitation of FM systems?
possible radio interference
What is the limitation of soundfield FM systems?
How can a soundfield system help?
help all children in the class hear the teacher's voice better.
for children who are hard of hearing or have mild to moderate hearing loss or cochlear implants
What is an assistive device for a telephone?
telecoil or tcoil
When fitting pediatric infants, what should be considered?
Use probe microphone to assess increased output of the hearing aid due to the smaller ear canal residual volume, known at RECD. Real ear coupler difference