CDO 431 AuD Rehab Amplification

• Many choices in amplification devices
• 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

• microphone
• amplifier
• receiver (speaker)
• battery
• 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.

• 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.

• 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
• Advanced features: feedback control, noise reduction, automatic, connectivity...

Loud sound --> compressed sounds

Loud sound --> no compression

• 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.

• 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

NO

• Volume 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

• Steady state noise can be filtered (gain reduced) to help reduce the“annoyance” of these sounds
• Must be a “noise” not speech

• Reduce acoustic feedback, without reducing the gain(volume) at that frequency
• Phase cancel
• the more power you need, the worse the feedback
• this allowed us to fit HAs that help patients with high frequency hearing loss

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
• In-the-ear (ITE)
• Half Shell (ITE or HS)
• In-the-canal (ITC)
• Completely-in-canal (CIC)
• 

• 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)
• Room available for added features

• BTE
• Large
• Exposed to external environments (moisture)
• Microphone external (wind noise, reduced pinnaeffect)
• Dexterity
• Earmold maintenance (tubing replacement)

• Slim tube: Acoustic transmission of sound through a small (slim) tube. Receiver is still located within the BTE case (similar to standard BTE). Uses a dome.
• 
• Receiver-in-the-canal (RIC or RITE): Electrical Transmission of sound through a small wire to the receiver which is attached to the wire and located in the ear canal. Uses a dome.
• 

• Smaller than traditional BTE
• Fits mild to moderately severe HL
• Fits HF hearing loss very well
• More comfortable (“lite”)
• Reduced occlusion (“open” ear canal)
• Can be stocked for instant fit (or loaned)
• Room for features (directional mics)
• Can be repaired easier in house (compared) to traditional BTE

• Need good dexterity for insertion/removal
• Can not stay truly “open” for more severe HL
• Exposed to external environments (moisture)
• Microphone external (wind noise, reduced pinnaeffect)
• Dome maintenance (filter and dome replacement)
• Available in “standard” sizes

• ITE or HS
• Smaller than BTE*
• Variety of gain options (can fit mild to severe)
• One part (less dexterity needed to insert and remove)
• Large enough for added features (directional mics etc.)* Phone use (T-coil)
• Microphone placement better than BTE
• *common-=recognizable, acceptable

• ITE or HS
• Not small enough
• Exposed to the ear canal environment (wax)
• Occlusion (venting options limited)
• Repairs require whole unit (no loaner option)

• ITC
• Smaller
• Still can fit directional microphones
• Fits mild to moderately-severe HL

• Can’t fit more severe HL
• More dexterity needed, due to smaller size
• Battery size decrease - hard to handle for older people
• Phone use (T-coils typically not available)
• Exposed to the ear canal environment (wax)
• Occlusion (venting options limited)
• Repairs require whole unit (no loaner option)

special part for using the telephone and for looped environments

place that have built in technology to link a t-coil hearing aid to the microphone being used

• a tab is pulled to allow air into the HA and charging the battery
• can be bought with no mercury, but these ones need 20-30 minutes of air before they can be put in and functional

batteries and we need to be sure the elderly patients are able to operate a smaller HA and change the battery

• Smallest custom instrument!
• Fits mild to moderate HL well
• Good with phone (no T-coil needed)
• Best microphone placement (less wind noise, increased pinna effect)
• Occlusion can be reduced (must be deep fitting - in the second bend of ear canal)
• Occlusion can be reduced for a lot of people, but it can also still be an issue because many people do not like taking the deep fitting impressions so the fit isn't as deep as it should be

• Can’t fit more severe HL
• Features are limited
• More dexterity needed, due to smaller size
• Battery size decrease
• Phone use (T-coils not available)
• Exposed to the ear canal environment (wax)
• Occlusion (venting options limited)
• Repairs require whole unit (no loaner option)

speech detection threshold

• no hearing at all
• only feeling sound

• to find out if someone is faking the test
• must be 20dB difference

• people who are faking a hearing loss
• 12 year old girls are common
• VA people
• people working on lawsuits

• Contralateral Routing of the Signal (CROS)
•   1 dead ear, 1 normal ear
• Bilateral Routing of the Signal (BiCROS)
•   1dead ear, 1 ear with hearing loss ( that is “aidable”)
• Bone conduction hearing aids
•   Conductive HL

• transmitter in bad ear and receiver in good ear
• allows the sound from the dead ear to be heard in the good ear

works like a CROS but has a HA in the good ear

• bone conduction HA is inserted on mastoid through surgery
• mastoid vibration --> osicle vibration -> cochlea

• artificial block that stops the mold from hitting the ear drum
• a string is attached to the block
• custom ear mold and hearing aid must use this type

• Many styles
• Many materials
• Some acoustical modifications
• Choice of earmold should be based on the individual HL, ear characteristics, hearing aid characteristics,patient factors (dexterity, allergies) etc.
• very individualized
• ear molds are usually hard plastic
• if the mold is for a child then they use more of a rubber material - silicone

• All hearing aids work with batteries
• Zinc Air
• Some rechargeable batteries are available (CIs, Siemens BTEs)

• 675- Large power BTEs, CIs
• 13- Common in traditional BTE and ITEs
• 312-Common in open fit BTEs and ITCs
• 10-small CICs and some open fit BTEs

• Whenever possible, it is recommended that individuals with hearing loss in both ears be fitted with bilateral amplification - 2 HA
• Some of the advantages of using 2 hearing aids include increased gain (volume), improved localization, better sound quality, and improved speech understanding in noise
• Better to have 2 low end HA than 1 high end

• Step #1: Selection the hearing aid candidate
• Step #2:Pre-selection measurements
• Step #3: Specific instrument selection

• audiogram
• HL
• communication difficulty

• measure how high they can handle sound
• measure length of ear
• diameter of ear canal
• ability to hear in noise
• NOAH - HA fitting softwear - assimilated fit

• provide options
• find out what they are basing their decision on

HA functions well

• ability of a HA to connect to other devices
• Bluetooth
• streamer and converters allow the HA o pick up electronic sounds

• Audiological needs (based on audiogram)
• Listening needs (based on goals and scales)
• Individual abilities (cognitive, eye sight, dexterity)
• Realistic expectations and motivation
• Cosmetic desires
• Financial limitations
• Desire/need for “connectivity”

• There is a balance to all of this
• You will never hear as well as you did as a child

• 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 expectations
• Instrument operation
• Occlusion effect
• Batteries
• Acoustic feedback
• System troubleshooting
• Cleaning and maintenance
• Service, warranty, and repairs.

• informal patient judgments of quality and intelligibility
• measures of speech understanding
• Loudness scaling (rating of loudness)
• probe-microphone measurements
• self-report measures (daily use time andsatisfaction/benefit) and data logging
• REL - real ear measurements

• 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

• manufacturers are working to improve function and performance of digital HA
• Ingress Protection (IP) rating
• 1st # indicates protection from solids (dust)
• 2nd # indicates protection from water