09_Intro to fitting graphs Flashcards
Describe the basic workflow of hearing aid fitting, starting from the hearing test, and ending at assessing outcomes
1) hearing test
2) RECD to assess ear canal acoustics
3) enter data into prescription (DSL or NAL or Camfit) and program aids
4) verify hearing aid output using calibrated speech signal (SPLogram)
5) fine tune the hearing aid response to meet targets
6) assess patient preference and outcomes
What is Boyle’s Law?
If the volume of the closed spaces becomes smaller, the pressure (i.e. SPL) becomes proportionally greater; if the volume becomes larger, the pressure becomes smaller
How do we measure the output of the hearing aid in the ear?
- probe tube placed in the ear, connected to a microphone that measures ear canal SPL
- hearing aid placed in the ear, and the system measures the HA output in the ear canal (using calibrated speech)
- *these systems can also analyze HA signal processing (e.g. distortion, battery drain, directionality, etc)
How do we interpret the fitting regarding:
UCL
Threshold
Smoothness
- Sounds above UCL will be too loud
- Sounds below threshold will not be heard
- Speech should be shaped smoothly and to target for comfort, sound quality, and intelligibility
Why do we graph in ear canal SPL?
- we can add hearing thresholds to the graph
- we can add UCLs to the graph
- this shows the hearing aid curve with perceptual landmarks (can’t graph thresholds and gain, which is the default display)
On some SPLogram displays, there is an upper and lower pink shaded region, with a white region in the middle, and a black line. What do each of the areas represent: Upper shaded region White area Lower shaded region Black line
Upper shaded region = UCLs
White area = auditory area
Lower shaded region = thresholds
Black line = aided speech
On the SPLogram with the pink shaded regions, what does the dark pink shaded area at the top represent? What do the red lines represent?
Dark pink = Max HA output
Red lines = DSL targets
What does LTASS stand for?
Long Term Average Speech Spectrum
When testing HA output, the speechmap software shows a coloured line in the middle of a shaded area. What do each represent?
- Coloured line = LTASS = RMS average (speech averaged over time to have a smooth, repeatable spectrum, which is measured in 1/3 octave bands)
- Shaded area = fluctuations in each band, used to calculate peaks and valleys from the percentile distribution
The shaded region above the LTASS is approximately the 99th percentile of speech level. Approximately how many dB is this?
12 dB above LTASS
The shaded region below the LTASS is 18 dB below the LTASS and represents approximately the __ percentile
30th percentile
Measuring short periods of time (125 ms) shows that speech varies by 30 dB. Which setting would this be on the SLM (fast or slow)?
Fast
Which language is the ISTS recorded in?
The ISTS is a language-neutral unintelligible speech passage of female talkers speaking in about 10 different languages, all spliced together
- developed by Europeans
Do the spectra of phonemes tend to occur in the area above or below the LTASS? What does this mean in terms of audibility?
Above; this means the upper region is more important that the lower region for audibility
Once the RMS and peak levels are all measured, they provide the raw data needed for the _____ to be calculated
SII (Speech Intelligibility Index)
