Final Exam - Lectures Flashcards
How does NAL-NL prescribe maximum output?
- Simplistically: the maximum SSPL likely to be acceptable at each frequency is assumed to equal the LDL of the person at each frequency. NOTE: does not allow entry of measured LDLs.
- The minimum SSPL likely to be acceptable is assumed to be the point where speech peaks start getting clipped (assuming peak clipping is the means of limiting). NAL assumes this to be 75 dB SPL input + NAL gain.
What does NAL software prescribe?
- Insertion gain curves
- Input-output curve
- REAG curves
- Coupler & ear simulator responses
- Crossover frequencies
- Compression Thresholds
- Compression Ratios
- Gain for 50 dB SPL input
- Gain for 65 dB SPL input
- Gain for 80 dB SPL input
How does NAL-NL prescribe compression?
- CR: prescribed for each channel
- Crossover frequencies: prescribed by audiogram configuration
- CT: defaults to 52 dB SPL; NAL believes that soft (50 dB SPL) speech should be just entering compression. Assumes lower levels are not very important or are noise. Also, NAL studies showed listeners preferred CTs ~ 60 vs. CTs ~ 50.
- AT/RT: not prescribed (although Dillon thinks dual compression is best)
What’s different in NAL-NL2?
- Dead regions: If a particular frequency region contributes little to intelligibility, we don’t want to amplify much in that region. (don’t want to add to overall loudness when there’s no intelligibility benefit)
- When gain isn’t provided, frequency response has a smooth roll-off (NAL-NL1 just didn’t give any values when gain wouldn’t improve intelligibility)
- Gain reduced ~4 dB at mid-input levels, and more at high input levels, compared to NAL-NL1 (based on listeners’ preferred gains)
- Lets user specify fast or slow compression and adjusts gain/compression characteristics accordingly
DSL v 5.0 goals
- Avoid loudness discomfort
- Ensure audibility of important cues in conversational speech as much as possible
- Prescribe compression appropriate for the degree and configuration of the hearing loss, but attempt to make a wide range of speech inputs available to the listener (audibility again!)
- Goals: audibility and comfortable loudness of important speech cues (NOT loudness normalization)
DSL v 5.0 features
- Groups i/o calculations together to create channels, each unified by a set of compression characteristics
- Everything specified as dB SPL in ear canal (does not prescribe REIG targets)
- Predict real ear SPL using the RECD, then fit the hearing aid in a coupler (helpful for kids!)
- Corrects for conductive (+25% of 4-freq ABG)
- Corrects for binaural (- 3 dB)
- For speech in noise, lower gain & higher CR.
DSL for Children
- Higher gain & output for children/congenital loss
- Lower gain & output, lower CR for adults
- Age-appropriate RECDs (specified in months)
- Allows for conversion of tone-burst ABR thresholds from nHL
- Child-specific input speech spectra
DSL v 5 stages:
(1) Expansion
(2) linear gain
(3) compression
(4) output limiting
Hearing Aid Verification (Purposes of Real-Ear)
- confirms that the hearing aid(s) meet(s) a set of standards for quality control
- includes electroacoustic measurements performed according to the ANSI standard (ANSI-S3.22-2003)
- rules out excessive circuit noise, intermittency, and/or poor sound quality
- assesses physical fit through examination of cosmetic appeal, physical comfort/security, absence of feedback, ease of insertion and removal, ease of control, and placement of microphone port
- uses real-ear measurements to establish audibility, comfort, and tolerance of speech and sounds in the environment and to verify compression, directionality, and automatic noise management performance
- incorporates sound field functional gain testing when fitting bone-anchored hearing aids
Speaker Location
Speaker distance from patient: Should be close enough to receive a strong sound level at the ear without speaker overdrive, and reduce influence of other noises in the room.
Fonix 7000: 45 degree azimuth, 12” away from patient
Audioscan Verifit: 0 degree azimuth, 18-36” away from patient.
What types of signals can you use for real-ear testing?
Use speech or speech-like signals or disable digital noise reduction – otherwise the hearing aid will interpret the test signal as noise and attempt to reduce gain.
REUR
Real Ear Unaided Response
The SPL, as a function of frequency, at a specified point in the un-occluded ear canal for a specified sound field. Can be expressed in dB SPL, or as gain (dB) relative to the stimulus level
REOR
Real EAr Occluded Response
- The SPL, as a function of frequency, at a specified point in the ear canal for a specified soundfield, with the hearing aid in place and turned off. Expressed in dB SPL or as gain (dB) relative to the stimulus level
REAR
Real Ear Aided Response
- The SPL, as a function of frequency, at a specified measurement point in the ear canal for a specified soundfiled, with the hearing aid in place and turned on. Expressed in dB SPL or (less commonly) as gain (dB) relative to stimulus level
RESR
Real Ear Saturation Response
The SPL, as a function of frequency, at a specified measurement point in the ear canal with the hearing aid in place and turn on. Stimulus level is intense enough to operate the hearing aid at maximum output (typically 90 dB SPL)
REIR
Real ear insertion response
The difference, in dB as a function of frequency, between the REUR and the REAR measurement taken at the same measurement point in the same soundfield
What is REAR minus REUR?
If expressed as gain relative to stimulus level, you may see REAG or REUG. REIG is always “gain” relative to unaided response.
What levels do you test REARs?
60
70
80
Why do we do REAR measures?
accounts for the aid (including earmold effects, like venting) and the ear/head. It realls to the sound level at the patient’s TM, regarless of what influences that sound level (ear or aid). It is easy to consider in terms of dynamic range/audibility
REIG
REIG = REAG - REUG
REIG tells you what the patient is getting with the hearing aid that they didn’t have before.
Requires you measure an inidividual REUR (or you can use average REURs, but they won’t account for your patient’s individual ear canal effects)
Which to use, REIR or REAR?
•
REIR (has fallen out of favor among clinicians):
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Tells you what the patient is getting with the hearing aid that they didn’t have before
–
Requires you measure an individual REUR (or you can use average REURs, but they won’t account for your patient’s individual ear canal effects)
•
REAR:
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Just tells you the sound level at the patient’s TM. Doesn’t care where gain comes from (ear or aid)
–
Easier to consider in terms of dynamic range (threshold to UCLs) to assess audibility
What is important while measuring RESR levels?
Be sure the RESR is not exceeding LDL levels – make any necessary MPO adjustments. Remember general complaints of “loudness” may be the MPO, or perception of lower levels
RECD
The RECD procedure consists of: (1) a 2cc coupler-based measurement and (2) a real-ear measurement. The 2cc coupler measurement is made on the same coupler used for hearing aid fitting. A transducer from the real-ear system delivers a signal into the coupler and defines the SPL of the signal as a function of frequency. Most probe-microphone systems have the capability to permanently store the coupler response
The same signal is delivered from the same transducer into the ear via a custom earmold or foam tip. The system again measures the level of the signal (this time in the ear) as a function of frequency. The difference between the signal on the ear and the coupler is the real-ear-to-coupler difference.
Instead of using the signal from the real ear system, you can measure RECD with an audiometer and insert phone (shown here) or with the same hearing aid, same earmold, same settings. The only requirement is that the sound source be exactly the same for both coupler and in-ear measures.
Potential problems doing real ear with open fits
- sound escapes from vent/open canal and “tricks” the reference mic into thinking there is more sound from the speaker than there really is
- reference mic thinks it is output from loud speaker, and so loudspeaker output to ear is turned down
- the result will be less measure hearing aid output
Solutions to problems doing real ear with open fits:
Solution #1: calibrate or “level” the equipment, then turn the reference mic off.
Solution #2: If you can’t turn off the reference mic, you could try lowering the reference mic (recall that distance away from the point of leakage is one of the factors).
Solution #3: You could simply assume that you’re making ~5 dB error around the peak of the REAR
Suggested Test Order for Real-Ear
1.
Enter audiogram into real ear system
2.
Choose prescriptive target
3.
Retrieve client data and connect aid. Program to first fit for the same prescription as will use in real ear.
4.
Otoscopic exam
5.
Verify physical fit, cut earmold tubing if BTE
6.
Instruct patient on real ear, place probe mic
7.
Measure REAR and adjust to match conversational target (adjust overall gain, frequency-gain bands)
8.
Measure REARs and adjust to match for soft/loud targets (adjust soft/loud gain, compression)
9.
Measure RESR and adjust at/below LDLs (adjust MPO)
10.
Verify directionality
How close to target do you need to be for real ear?
•
Two separate sources (Dillon & Fabry) suggest:
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Aim to be within 5 dB of target from .25-4 kHz. As much as 10 dB deviation may be ok in some cases.
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When all measures are above target (or all are below) can be corrected with VC adjustments. If below target at some frequencies and above target at others frequencies (poor match to slope), consider adjusting
–
Try to match soft speech target, but remember goal is audibility while maintaining appropriate range of loudness (soft speech should sound softer than conversational speech)
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Try to match loud speech target, but remember goal is loud but ok, while maintaining appropriate range of loudness (loud speech should sound louder than conversational speech)
Using Real Ear to verify directional microphone
•
Compare 0 to 180 degrees (or the null of the polar plot, if not 180 – you can let the signal play and rotate the patient until the response is at its lowest point) at same level
•
Verifit’s Directional Test uses two speakers at 0 and 180 degrees
- presents over 1000 tones simultaneously at different frequencies from both front and back sound-field speakers. Tones are individually controlled to produce a precise spectrum from each speaker at the on-ear reference mic
- The ear canal SPL is analyzed into two real-time response curves, labeled F (front) and B (back) to indicate which speaker generated the curve.
Some Real Ear topics for discussion/Practice
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Matching a single-level target (how close is close enough, and how to get there quickly)
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When not to chase the target (considering severity of loss and dead regions – usually high frequencies)
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Matching multiple targets (when to adjust overall gain versus compression)
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Verifying signal processing (directional microphones, digital noise reduction, frequency lowering)
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Understanding real ear for open canal fittings (hint: you can’t affect the lows by changing hearing aid settings). Also when to give up and use an occluding earmold.
•
Fitting conductive losses
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Using non-standard signals as demos/counseling
Conversions between measurements in real ear
The RECD is the difference between output in the coupler and output in the ear. The CORFIG is the difference between gain in the coupler and gain in the ear. CORFIG considers: that when an aid is placed in the ear, the REUR is lost; the RECD is gained, because the ear is smaller than the coupler; and there may be some resonance because of the position of the microphone (only for ITE/ITC/CIC).
REAR – 2CCR = RECD REAR – REUR = REIR Target REIG + CORFIG = Target 2CCR 2CCR + GIFROC = REIR or 2CCR – CORFIG = REIR CORFIG = REUR – RECD – AID/MIC EFFECT AID/MIC EFFECT IS NEGLIGIBLE FOR BTES
Hearing Aid Validation
1.
documents that the disability has been reduced and audiologic treatment goals have been addressed
2.
includes self-assessment tools that measure benefit and satisfaction
3.
measures speech perception using either objective or subjective techniques. The effects of stimulus selection, presentation levels, noise type, signal-to-noise ratio, and the number of test items on the reliability and validity of speech perception measures should be indicated.
What are the three WHO concepts that effect a health condition (disorder/disease)
- Body function & structure (Impairment)
- Activities (limitation)
- Participation (restriction)
Within these there are environmental factors and personal factors.
What are the two types of measures when assessing hearing?
objective and subjective
What are some objective hearing measures for determining hearing aid needs?
speech in quiet
speech in noise
aided threshold (functional gain)
audibility (aided threshold + count-dot audio)
What are some subjective hearing measures for determining hearing aids needs?
sound quality ratings
loudness ratings
questionnaires
What are some questionnaires that are customized, individual (“open ended”)
- COSI (benefit, direct change)
- GHABP (disability, handicap, use, benefit, satisfaction)
What are some questionnaires that are standard (“closed ended”)
- APHAB (benefit, activity limitation)
- HHIE and HHIE-S (handicap/participation, restriction, pre-post state)
- SADL (satisfaction, post)
- IOI-HA (benefit + satisfaction + HRQoL)
What makes a good self assessment measure?
• Relevance • Reliability • Inter-patient variability • Appropriate for population • Well-validated • Easy to administer and score • Short • Administered after benefit, etc. has stabilized (suggest ~ 6 wks post-fit)
Self-assessment measures
• At evaluation – Helps determine candidacy – Helps identify unrealistic expectations – Good audiometric candidate, but poor motivation • At follow-up visit to assess HA benefit – Is benefit adequate? • Direct • Unaided vs aided comparison – Identify situations needing improvement
Problems with self-assessment tools
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Patients may not like, or will not complete
•
Audiologists may not like to administer and/or score
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Standard questionnaires may not identify specific priorities
•
Some patients may have difficulty understanding complex questionnaires (note availability of questionnaires for CPs, such as the IOI-HA-SO and SOS-HEAR)
Therefore….COSI
COSI
- at consultation, patient identifies 3-5 listening priorities
- after fitting, patient rates
- degree of change with hearing aids
- how well they can hear in that situation now
If the COSI was completed prior to fitting, the patient can assess the amount of improvement with the hearing aid
- is included in some manufacturer’s modles with NOAH
Self-assessment tools assessing multiple domains
Glasgow Hearing Aid Benefit Profile (GHABP, 1999)
•Assesses 6 domains: Hearing Handicap, Hearing Disability, Hearing Aid Use Time, Benefit, Residual Disability, Satisfaction
•Provides 4 situations and can nominate 4 individualized situations
International Outcomes Inventory (IOI-HA, 2002)
•7 questions: Hearing Aid Use, Benefit, Residual Activity Restriction, Satisfaction, Residual Participation Restriction, Impact on Others, QoL
APHAB
- 24 questions across 4 domains
- 7 point response
- unaided and aided
- computer or pencil and paper version
- Ease of Communication (EC scale)
- Background noise (BN Scale)
- Reverberation (RV scale)
- Aversiveness (AV scale)
- global score (average EC, BN, RV)
Using the APHAB
•Unaided –Assess candidacy –Select appropriate features •Measuring benefit –Decreased disability in each subscale –Compare to norms to decide to keep (borderline) •Troubleshooting –Identify situations w/ low benefit –Assess expectations –Consider technology change
SADL
• Post-fitting (can use ECHO pre-fit) • 15 questions (Reversed items 2, 4, 7, 13) • 7-scale response format • 4 subscales – Positive effect (decreased communication problems, better self confidence, sound quality – Service and cost (reliable, clinician, $) – Negative features (BN, phone, FB) – Personal image (appearance, others’ opinion) (+ Global score)
What are three reasons to educate the patient?
- provide realistic patient choices
- encourage self-efficacy
- convey sense of unique issues and abilities (one size does not fit all)
Principles of self-management
- targeted assessment
- evidence-based information to guide shared decision making
- collaborative problem solving
- patient self-efficacy (choices)
- active follow-up
- multifaceted intervention
Medical Model
- top-down communication
- authoritarian
- clinician determines diagnosis and treatment
- clinician does something “to” client
- assumes clinician knows what is best for client
