I. Optimal Aids
A. Types of Aids
1. Body aids- not used much now but have greatest _____ and least feedback and most durable.
2. BTE- Behind-the-ear aids are used mostly by children and can be used with FMs. Mic at ear level gives better localization. Binaural fittings eliminates _______ effects. BTE’s now have high gain and low feedback. Use "huggies" to keep on ear.
3. ITE- In-the-ear aids are used mostly by adults. Direct sound input into ear canal. Controls are smaller and fewer _______ are possible. Manufacturers will recase as child grows so more practical for children now. However, use of ITE encourages hiding the hearing loss which is undesirable. (80% of HA market)
4. ITC- In-the-canal aids have less gain than ITE’s and are typically not used with children
5. Open Fitting-small BTE with thin tubingAnd open coupling tip
6. Receiver in the Canal- RIC-SmallBTE _____________ the pinna to receiverIn the canal in “mushroom” tip or in custommold7. Vibrotactile- Was used when ___________________. Two-channel vibrators for ____ and ___ frequencies may be worn on sternum. The user got primarily _______ and ______ cues. Background noise can be a problem as the continuous vibrations may easily mask the vibrations for the signal.
8. CROS- Contralateral routing of offside signal- One mic on ____ ear picks up sound and delivers it via wire or FM signal to ____ ear which has the amplifier and receiver. In a BICROS arrangement, there are ____ on both ears but the _________ and ________ are only on the better ear.
9. Cochlear implant- May be considered only after there has been no benefit from other types of amplification. Mic on ear sends acoustic signal down to _________ worn on belt which codes the speech information into electrical energy which is sent back up to implant in skull via _______________ induction or a ____________ plug.
B. HA Options
1. Basic parts in all aids
» Mic- changes sound to electric signal.
» Amplifier-Increases the intensity of the electrical signal.
» Power Supply-provides power to the mic and amplifier.
» Receiver- converts elec signal back to sound.
2. Telecoil-Mic-Off Switch- MTO Best arrangement on a HA is to have M--MT--T options. T allows the pickup of an electromagnetic signal which is very useful if there is much background noise. Two problems with T-coils are: increased _____ and reduced ___ frequency gain. In a personal FM arrangement, if the HA doesn’t have MT, then use the environmental mic on FM receiver and receive the FM signal via the T-coil on HA.
3. Tone Control- Often labeled N-H-L which refers to the frequencies the HA will emphasize.
4. Horn ear Hook or widened bore- allows ____ frequency emphasis (good for sloping losses).
5. A peak-damping ear hook smooths out the peaks of the output to make it a more flat output across freqs.
6. Vent- allows ___ frequencies to escape and allows ___________ of ear canal pressure (good to use with mild/moderate losses, not with severe ).
7. Output controls- Maximum output of the hearing aid may be controlled by _____________ or ___________. Limiting output by ___________ is most desirable because there is no disruption of the ________.
8. Direct Audio Input- A ____________ connection to the hearing aid from a TV, microphone, FM receiver, etc. When used with an FM, it is ideal to have the following three signal options: ENV only, ______, and FM only. Retrofitting services- Before adding more options later, make sure your HA is equipped for the option and that you won’t be giving up other options in the process.
9. Volume Control- Should always be at 2/3 or less (use setting). Never fit hearing aids with volume setting at _______. Some HA don’t have one, they automatically monitor the gain. Volume controls are not linear, i.e. turned up halfway doesn’t give half the gain. Number controls are different for every HA.
10. Directional Mic- A second mic port results in the reduction of sounds from ____. Hawkins (1984) has shown that directional mics on HA’s result in the best speech recognition when used in FM arrangements.
II. Consumer Aspects
A. Price- BTEs are _______. Price may include testing, fitting, followups.
B. Insurance- It is important for children’s aids to be covered for accidental loss from manufacturer or outside company; also maintenance and preferably a ___ yr warranty.
C. 30-day Trial Period- should be able to return for a near full refund. However, trial period is not ________ in all states.
D. Repairs- Would want fast turn around and the use of ______ during repair
E. Batteries- 675-larger; 13-smaller; 312- flat smaller in ITEs. There is also Nicad which are rechargeable.
F. Earmolds-
_______ (soft- good for kids);
_______ (harder for adults);
Hypoallergenic (opaque in color).
Change to new earmolds: 0-2yrs old, every 4-6 mos.; 2-6 yrs old- every yr;
6-14 yrs old- every 2yrs.
G. Care and Use of Hearing Aid should be thoroughly discussed during the dispensing process
H. Followup services are very important. Children will need hearing aid check every 6 months or sooner until about age ____ after which annual checks are acceptable
III. Hearing Aid Selection
A. Behavioral Hearing Aid Evaluation (Approx. 2 hours)
1. Obtain ____________ thresholds and ____________s if possible!
2. Determine relationship between ____________and speech spectrum.
The gain for the HA needs to allow the speech spectrum to be ____________ without exceeding ____________. Use gain values recommended by Ross and Seewald or some other prescriptive formula. Ross and Seewald’s approach is to amplify speech to a ____________ which is less in the ____________ frequencies because of the concern for ____________. (See their Figure __). One quick estimate for gain is the ____________rule which states that the gain is half the threshold value at that frequency except at 250 and 500Hz. Subtract 10 and 5 dB at those frequencies respectively.
3. Determine target aided thresholds.
If the threshold is ____________ and the desired gain is ____________, the target aided threshold is ____________.
4. Select hearing aid that allows the desired amount of gain.
Based on manufacturer specifications and corrections for real-ear response, find aid with potential for desired gain.5. Measure the gain provided by the hearing aid.
Measured gain = Unaided 0 - ____________. This is the ____________ gain.6.Evaluate speech recognition.
May determine ____________score using appropriate materials if time allows.
However, don’t forget....... It is not productive to compare hearing aids based on performance with ____________ lists because the differences are likely to be ____________ than what would be required to demonstrate a significant difference according to tables provided by _______ and ________.7. Setting the UCL
Measure it at each frequency or just for speech. (In which case, it will usually reflect UCL for ____________ Hz.) On HA there is only ____________ that accounts for all frequencies. If dynamic range is small, the SSPL90 may be set at UCL; otherwise it should be ____________. Ross and Seewald provide a chart illustrating recommended settings based on the difference between the UCL value and the ____________ speech spectrum (their Figure __). For children, a target aided threshold of 20dB HL is often advocated, but this may result in ____________ for some kids because it would cause the speech spectrum to fall at UCL and limited by ____________. Speech recognition would be reduced because users are no longer getting the ____________ ____________. The key is that one must consider the ____________ speech spectrum which is the normal speech spectrum plus the ____________ of the hearing aid.
B. Probe Microphone Measures
This procedure is done to quickly determine if the gain is ____________!
The purpose is to determine the ____________ gain of a given HA by comparing the SPL in and unaided ear canal to the SPL in an aided ear canal via a ____________placed in the ear canal that collects sound and directs it to a small mic.
These measurements are very ____________, reliable, and fast.
This is the most desirable method to evaluate a hearing aid fitting.
There is a ____________ mic to monitor the level of sound reaching the probe mic.
If the client moves, the sound source will know to increase or decrease the intensity of the signal so it will remain constant. This testing can be done outside the sound booth because room noise is accounted for.
Equipment is as follows:
Take a closer look at the Steps Involved in Probe Microphone Measures
1. Calibrate reference mic relative to the speaker. It is attached at ____________ to be close to the HA ____________. Level the system so that sound arriving at the ear is appropriate. During the leveling process, corrections are determined so that the sound arriving at the ____________ is what is requested.
2. Measure unaided response to a 70 dB SPL signal. The ear canal itself will provide some amplification without a HA at about ____________ Hz (____________). The natural resonances of will vary with ear ____. ____________ canals resonate at a higher frequency and result in higher output than ____________ canals. With an 80dB input, in a long canal the output may be 90dB and in a short canal it may be 100dB.
3. Put HA on and measure aided SPL with a 70 dBSPL signal.
4. Take aided curve minus the unaided. This is the ____________ which should agree closely with the ______ gain.
Common Abbreviations:
REUR- Real Ear Unaided Response
REAR- Rear Ear Aided Response
REIR- Real Ear Insertion Response
REIG- Real Ear Insertion Gain
NOTE: To fit a HA with a flat gain (i.e. same functional gain at all freqs) you need to start with a HA that gives more high freq ____________ gain than low to compensate for the loss of the natural ear canal resonance that occurs when the earmold is inserted.
REMEMBER.....The goal is not to achieve near normal thresholds, but to amplify speech so that is above threshold and below UCL.
C. Electroacoustic MeasuresThe standardized procedure is regulated by __________ (1980) specifications required by the FDA. HA is checked using a __________ that simulates characteristics of the ear,
but .......it is not an entirely accurate representation. (However, a __________ coupler is an accurate representation.)Equipment is as follows:
Measurements:
1. Gain = output- __________ when a 60 dBSPL signal is presented across frequencies. A mild amount of gain is 25-40 dB, a moderate amount is 40-55 dB, and a high amount is __________ dB.
2. High Freq Average Gain = the average gain at __________, 1.6K, and 2.6K Hz.
3. Full On Gain = The gain is determined when the volume set to __________ and an input of 60 dB SPL is used. Certainly don’t want to wear the hearing aid at full on so the next measure is done at a lower setting.
4. Reference Test Gain = Gain is determined at a simulated __________ volume control setting. This setting is defined in the standard such that it is a predictable amount below full on. A family of curves may be provided indicating that there is ____ control.
5. Maximum Power Output = SSPL90- Saturation sound pressure level when input is 90dBSPL and volume is __________. Obtain a max output curve across freqs. A family of curves may be provided indicating that there is an __________ control.
6. High Freq Average SSPL90 = the average max ouput for 1K, __________, and 2.6K Hz. The gain and max output are measured across frequencies and represented as curves.
7. Harmonic Distortion = Volume control at RTG, input at 70 dB SPL. Get % of total energy due to energy at __________ of the input. Optimal= 0% to 5-6%, 10% max.
8. Equivalent Input Noise(EIN) = noise generated by the HA itself. With the volume at RTG , the output is measured in the coupler while there is __________. The gain is subtracted from this level to get EIN. Typical amt of noise in HAs is __________. If the HA had 50 dB of gain then the level in one’s ear canal just due to the noise of the hearing aid may be _____ to ____ dB SPL. This is why some with mild losses have trouble with HAs.
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