08_Intro to prescriptive targets and fitting Flashcards
What is a prescription?
A mathematical formula, sometimes implemented in the software, that recommends the decibel levels that should come out of the hearing aid
What is the difference between the REUR and REAR called?
Gain
What are the 3 major concepts regarding hearing aid output?
1) loudness normalization requires more overall gain for soft sounds and less gain for loud sounds (compression)
2) modern HAs can adjust gain quickly, in real time, and in many channels
3) HAs shape the output of speech to account for the shape of the hearing loss and the falling spectrum of speech (frequency shaping)
Name two things targets help us provide.
- good speech intelligibility in quiet, by providing enough frequency shaping to ensure access to many/all sounds in speech
- comfortable, acceptable loudness
- reasonable subjective outcomes (good benefit)
The use of published prescriptions is typically considered part of _______
Evidence-based practice
Where are “generic” HA prescriptions developed? Are they specific to certain makes and models of HA?
Developed in research labs.
Not specific to any make or model of HA (typically do not recommend a specific profile of signal processing)
Revised over time based on research
Name 3 families of generic prescriptions that are active, and one feature about each
DSL - developed in Canada, originally for paediatrics
- adult version available
- current version DSLv5
NAL - from Australia
- current version NAL-NL2
- typically for older adults c/ hearing loss
Camfit - from English
- current version Camfit-HF
- has targets to 10 kHz
What might not be present in all prescriptions?
- formula may not be adjusted for linear vs non-linear signal processing
- formula may not adjust itself to provide more gain and output for children who are acquiring language, or corrections for pediatric EAMs or ax methods
- formula may not include targets for the extended high frequencies
What are “propietary” prescriptions?
Prescriptions developed by individual manufacturers for use with their HAs
- based on in-house studies, feedback from partnered clinics, and theoretical principles
- intended to provide good initial fitting
- typically associated c/ recommended signal processing profile (default setting for NR, programs, etc)
- combined set of default settings and signal processing sometimes gets proprietary name (FirstFit, Autofit, etc)
How can generic and proprietary prescriptions be used together?
Can usually select an HA prescription together with default signal processing
- e.g. generic prescription for speech in quiet + proprietary default signal processing
Which prescription includes corrections for input level, adults vs children, and quiet vs noisy situations?
DSL
Which prescription includes corrections for input level, adults vs children, and tonal vs non-tonal languages?
NAL
Name 2 reasons why the HA instrument type is important to include when working with fitting software?
- keep accurate record
- set the system for active vs stored equalization at the ref mic
- set the correct mic location effects if using test box verification
When do you select test box vs on ear mode for fitting software?
- on ear if it is on the patient
- test box if you wish the system to use MLEs and RECDs to enable coupler-based testing with corrections
How does the HL transducer affect targets?
Different audiometric transducers use different procedures for the HL to SPL transform, to choosing the right menu item ensures the correct transform is used
