Advancements in electronics and computer technology allow devices to reproduce amplified sounds and speech for individuals with hearing loss with considerably higher fidelity and output levels than ever before
Only 1 in 4 people who could benefit from a hearing aid actually wears one
Audiologists have the formidable task of informing the general population about amplification products and services and dispelling many of the misconceptions that currently exist today
Hearing Aid Components
Behind-the-ear (BTE) instruments also require an ear mold or slim tube/receiver unit and dome to channel the sound into the ear canal.
Parts of a Hearing Aid
Hearing Aid Technology
Hearing aid circuits can be either analog (mostly a thing of the past) or digital (more advanced and more common)
Digital processing, introduced commercially in 1955, is the current standard
Two key components, the microphone and the receiver, however, are the same for both digital and analog technology
Analog hearing aids sound different then the digital ones. For people who have severe to profound hearing loss will ask for an analog because they admit loud harsh sound.
The advantages of digitally programmable technology:
BETTER SOUND QUALITY
The way the hearing aid processes sound can be adjusted and tailored for the individual patient
Manufacturer computer software can be upgraded and new features can be retrofit to existing hearing aids
Audiologists (and patients) can be the decision makers
Compression is a feature which controls the maximum output of a hearing aid. Compression also has the ability to package sounds into a certain range that is both audible an comfortable for the patient.
Input compression controls the sound before it reaches the amplifier. This helps keep sound within a patients dynamic range.
Output compression controls the sound after it reaches the amplifier. This helps limit the overall volume for loud sounds.
Most digital hearing aids have both input and output compression on the digital chip - like a small computer
A popular category of compression is termed wide dynamic range compression (WDRC). It is available in all the current digital products and is especially useful for providing audibility of soft speech. Keeps speech within the individuals “Dynamic Range”.
Microphone technology has been an area of huge research and development for hearing aid manufacturers.
Omnidirectional microphones vs. directional microphones
The goal is to increase the SNR for the hearing aid user.
Technology Frequency Specific Gain
The frequency range is separated into individual“bands” or “channels” which can be individually adjusted.
Allows more specific fitting for individual hearing loss
Allows for fitting of unusual configurations (ex. rising)
Better suited for precipitous losses with large changes between frequencies.
Signal to Noise Ratio
allows hearing only in front of your head. Great for loud rooms / areas
research only proves that directional microphones increase SNR by 6 dB
allows hearing all around your head - great for quiet rooms
Can any technology bring down the overall background noise
Technology Gain control
User adjusted wheel, switch, toggle, remote control
Automatic gain control (type of input compression), digital
studies show that people are bad at adjusting their volume and therefore automatic adjustment better
there are newer HA that have artificial intelligence which allows them to learn and train the HA to auto adjust based on characteristics of sound input
Technology Digital Noise Reduction
Steady state noise can be filtered (gain reduced) to help reduce the“annoyance” of these sounds
Must be a “noise” not speech
Technology Digital Feedback Control
Reduce acoustic feedback, without reducing the gain(volume) at that frequency
the more power you need, the worse the feedback
this allowed us to fit HAs that help patients with high frequency hearing loss
Technology Frequency Transposition
Manipulate the frequency of amplification, so that “dead regions” of sound are moved to a functioning frequency band (functional hair cells).
Styles typically are referred to by their location in theear.
Behind-the –ear (BTE)
Traditional BTE and open fit BTE or mini BTE
Half Shell (ITE or HS)
% of hearing aids used
BTE (≈ 50% of market today*)
Large variety of power (gain) available (& larger battery)
Separate the microphone form the receiver (decrease fdbk)
Separate the mechanics of the instrument from the ear canal environment (decrease breakdowns)
Children- earmolds can be soft, earmolds can be remade forlittle cost, earmolds can be washed
Earmolds can be modified on site
Option to stock the instruments to fit on demand (or loan)
Hearing Aid Validation Electroacoustic evaluation (EAA) (step 4 in book)
Hearing aids are assessed, both at the manufacturer and in the clinic by EAA (using 2 cc coupler)
The results are used to determine if the hearing aid meets a set of established specifications
These results do not assure that the hearing aid is appropriate for a given patient
validate that it is functioning as it should
Hearing Aid Orientation
Cleaning and maintenance
Service, warranty, and repairs.
Hearing Aid Verification
can include the following
informal patient judgments of quality and intelligibility
measures of speech understanding
Loudness scaling (rating of loudness)
self-report measures (daily use time andsatisfaction/benefit) and data logging
REL - real ear measurements
Hearing aid Verification The Probe Microphone
When prescriptive fitting procedures are used, probe microphone measures are the preferred method for determining if desired gain and output values have been achieved.
When fitting hearing aids to infants and children, it’s important to remember that because of their small ear canals, the output of the hearing aid will be greater than with adults. Probe-microphone measures (real ear measurements) can be used to determine this difference value.
listens to sound after amplification and before it hits the ear drum
infants and young children - output of HA will be greater than with adults
In addition to hearing aids, many individuals can benefit from assistive listening devices (ALDs) or hearing assistive technologies (HATs)
Special listening situations (e.g., amplifier for the telephone)
FM or Infrared for the classrooms or large auditoriums
Device for listening to the TV
Alarms and other alerting devices
you can ask for accommodations for HL if needed
you can ask for a hearing impaired room at hotels
New Level of Performance
manufacturers are working to improve function and performance of digital HA