what are the different ear mold styles?
standard mold --carved shell -skeleton mold --semi-skeleton canal mold --canal lock, canal, hollow canal Cros -A (part concha-rim cut out and full canal), B (full concha with full canal), C (full concha with short canal)
peri-tympanic
where the CIC sits, deeply seated
IROS vent
when the vent path in the ITE/ITC is opened out by removing some of the shell at the medial/lateral ends of the vent leaving the vent path
problems with the Y vent design
HF sounds propagating down the sound bore will be partially reflected @ the Y junction.
- this decreases HF gain
- makes HF feedback oscillation more likel
disadvantages of open-canal fitting
- gain-frequency response
- avoids own-voice occlusion
- feedback oscillation
- microphone directivity and adaptive noise reduction
- prescription targets and real-ear gain measurements
reasons to mix impression material with a spatula and disposable pad/cleanable surface
- adverse health consequences for clinicians from repeated absorption of chemicals
- contaminating impression material w/sulfer based substances that leak from hands or latex gloves
- raising the temp. of the impression material because setting time decreases
input controlled compression
volume control is after the compressor in the HA.
compression commences at the same input SPL for all setting of volume control.
once the compressor has done its job, the volume control determines the size of the output signal. the curve moves up and down as volume control is varied
output controlled compression
volume control affects signal BEFORE the signal reaches the compressor. the curve moves left to right.
if the volume gets controlled down, then the compression factor may not be necessary because the initial volume is down.
shapes of polar directivity pattern
cardioid super-cardioid hyper cardioid figure-8 / bi-directional (sensitivity lobe)
wiener filter
the signal power divided by (signal power + noise power)
what should a comprehensive evaluation of frequency lowering measure?
- ability to detect HF speech sounds and environmental sounds
- ability to identify a wide range of consonants with high representation of fricatives from female voice, but not restricted to HF consonants
- detection and ID in both quiet and in noise
- impact on speech production
- changes in these abilities over several months
what are some aspects of speech cue enhancement?
enhancement of: spectral shape consonant-to-vowel shape duration re-synthesis transient enhancement speech simplification
what can an audiologist tell by data logging?
- use of volume control
- if client is actually using the HA
- battery usuage
- use of programs
- usage of 1 HA compared with the other
- usage of a program for a short period of time, indicating a troubling environment for the patient
