Lecture 13 Flashcards
Why is verification of hearing instruments an important measure?
- When patients are fitted with this best practice they have higher satisfaction with their HAs
- Take up less clinic time because they are more satisfied
- Maximizing potential of audibility and benefit of the HAs we have selected
- There is no HA at a premium level that will outperform poor audibility and poor fitting (if we cant verify to target we are reducing benefit)
- Audibility is key
What does the verification of hearing instruments confirm?
Verification of hearing instruments (real ear measurements/REMs) is a practical procedure used to confirm that the hearing instruments are performing in a certain manner to provide appropriate benefit to the patient based on their audiological needs
What are the 3 verification measures?
- Objective
- Measured in Real-Time
- Provide Monaural data (vs. binaural benefits reported by patient)
How is validation different from verification?
- Validation: subjective measures (are you hearing better in a context that is important to you)
- Verification allows us to look at two hearing aids and how they are working to better performance together
Define Real Ear Unaided Responses/Gain
(SPL at the TM): looking at the response of the ear itself with no amplification present (what is the ear bringing to the table)
Define Real Ear Aided Responses/Gain
(Aided SPL at the TM): looking at sound delivered to the TM with the HA in place
How do you use REAR to determine fit to target?
- Solid line: long term average speech spectrum (want to see the range going directly through the targets)
- Bubble: shows 30th and 99th percentile
- LDL: what are the loudness discomfort levels
What is REAR really determining?
How much gain is being provided for soft, loud, and average inputs
How do you use REIG to determine fit to target?
This is what an insertion gain target might look like (not the most popular view of measurement)
What is the speech intelligibility index (SII)
- The Speech Intelligibility Index (SII) measures the amount of a given speech signal that is audible to the listener
- Ideal to use as a counselling tool, integrated into verification software, and helps to understand how much speech is available with and without the hearing aids. In combination with our matching to “target, the SII can be used to understand if the hearing aids are providing appropriate amount of audibility.
- The calculation of the aided SII is is done by evaluating the recorded aided response curve and the points where the aided response curve is higher (above) the hearing threshold of the patient.
- Different frequencies are given a different weight. For example, frequencies that are more important for speech intelligibility (e.g, 1500 to 3000 Hz), will have a greater impact on the SII.
SSI - what is percentile SII (picture)
- Percentile SSI: the score is a way of quantifying the intelligibility of speech based on the proportion of speech cues that are available
- This is a likely predication based on aided and unaided conditions
- SII of 20, predicted speech score in words and sentences is pretty low
- SII of 90 is better because getting 90% of words in sentences
SSI with and without aided thresholds (picture)
Without aided thresholds, SSI was 45, but with, its 75
What are the 5 pieces of equipment needed for verification equipment?
- Hearing Aid/Real-Ear Analyzer
- Sound Source
- Test Box
- Probe mic and probe tube
- Reference Mic
Explain how the probe mic and probe tube placement works
- Probe Mic measures the response, in the ear canal, in dB SPL (ideal for REUR, and REAR finding)
- Correct Placement of probe tube is essential for accurate REMs
- Placed to approximately 5mm of the TM (black marker to inter-tragal notch)
What happens if a probe tube isn’t in the correct place?
A probe tube not in the right place, the frequency response will tell you that you cannot reach gain
4 tips for probe mic and probe tube placement
- Clear Ear Canal (cerumen management if needed)
- Infection Control on retention cord and probe module
- Reference Mic facing outward
- Probe to to the front-side of the retention cord- stability and holding placement
How do you place a hearing aid in the ear with a probe tube
- The probe tube should not easily slide
- The dome should be sitting on top of the probe tube, but not pushing on it
What is the reference mic?
- Reference Microphone monitors the input from the loudspeaker to ensure that the signal delivered remains accurate and stable
- Reference microphones are in both the test box, and the on-ear probe module
- Reference microphones are active during the process of REM to monitor the signal
- Before each speech stimuli is presented, there is a “pssshhhh” sound that will be audible. This is the calibration for the reference mic
How do you set up a measurement in the verification device?
- This will include audiogram, fitting rationales, hearing aid form, coupling/venting options.
- Select test signals (sound and level) Special consideration for “open fit” (equalization)
What are the 6 procedural guidelines for completing a REM?
- Setting up measurement in verification device
- Positioning the patient comfortably (0° azimuth, directly in front of loudspeaker, within 45 to 90 cm ideally)
- Perform otoscopy: determine the need for cerumen management
- Probe tube insertion (placing probe tube, ideally in a clear canal, to appropriately depth)
- Reference mic positioning (facing outward)
- Checking in with patient (are they seated comfortably, ready to proceed?)
What are 2 reference mic considerations
- Open-fit devices require equalization prior to performing REMs
- Devices are on the patient, but are on “mute” (or turned off)
Why? Sound leaking out may effect the stimulus from the loudspeaker
Is an open-fit really an open-fit?
- REUR can provide insight
- If the two curves match up, it means with the HA in place, the two responses match up
- The second pic is showing what happens when the HAs are muted
- Generally run this when the patient is using a cap dome
What features do we have to select when doing a REM?
- Target: which rational are we using (make sure this is a match to what we programed in software)
- HL transducer: how was the HL measured in a sound booth (sound field, insert, headphone)
Why is it important to select the transducer type when doing a REM?
- How was the hearing loss measured in testing?
- To measures REMs, there is a conversion that occurs between the dB HL thresholds obtained, and the measured dB SPL at the eardrum.
- The conversion is partially based on the RETSPLs
What can impact probe-mic measures? Why?
- Cerumen in the ear canal can impact probe-mic measures
- Pathways of sound is modified (residual canal volume)
- Probe tube may be blocked by cerumen
- May be impossible to place the probe tube in the correct position depending on the location and amount of the wax
- Managing cerumen prior to REMs when necessary is the best way to get an accurate result
Explain how the loud speaker and patient location works
- Ideally away from reflective surfaces (right in a corner, reverberant surfaces)
- Ambient noise measurement tool to ensure room is quiet (should not be louder than soft speech inputs)
- Also to note: verification system should be placed where the audiologist can access all equipment, and move around the patient easily