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Audiology Review: Preparing for the Praxis and Comprehensive Examinations
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412
Explanation: OSHA (1983) and NIOSH (1999) both require that the baseline and annual audiometric evaluations include measuring pure-tone air conduction thresholds at 500, 1000, 2000, 3000,
4000, and 6000 Hz. Neither organization requires testing at 250 or 8000 Hz. Therefore, b is the
correct answer.
9. A newborn has been in the neonatal intensive care unit (NICU) for 7 days. Which of the
following would be the most appropriate hearing screening method to use based on Early
Hearing Detection and Intervention (EHDI) guidelines?
a.
Otoacoustic emissions for the initial screening and any rescreening
b. Otoacoustic emissions for the initial screening and automated auditory brainstem response
(AABR) for rescreening
Automated auditory brainstem response (AABR) for the initial screening and otoacoustic
c.
emissions for rescreening
d.
Automated auditory brainstem response (AABR) for the initial screening and any rescreening
Explanation: The Joint Committee on Infant Hearing (JCIH, 2007) recommends use of an automated auditory brainstem response (AABR) screening for newborns who stay more than 5 days in the
NICU due to increased risk of neural hearing loss. Use of the AABR allows for detection of auditory
neuropathy. Therefore, d is the correct answer.
10. A 7-month-old baby is seen for a diagnostic ABR test. Parents report the baby failed the
newborn hearing screening performed 7 days after birth and the rescreening performed
2weeks later. A diagnostic ABR was recommended, but the family was unable to attend the
appointment because the family moved to a different state for the father’s job. Due to challenges
in establishing a new pediatrician and obtaining a referral to a local audiologist, the child is now
being seen for his first diagnostic ABR. Results reveal a bilateral moderate flat sensorineural
hearing loss. The child is subsequently fit with bilateral behind-the-ear hearing aids at 8 months
of age. Based on Early Hearing Detection and Intervention (EHDI) guidelines, which of the
following statements is true regarding identification of the child’s hearing loss?
a. The initial newborn hearing screening should have been performed within 48 hours of the
child’s birth.
b. The newborn hearing rescreening should have been performed within 7 days of the initial
failed screening.
c. Because the child failed the newborn hearing screening and rescreening, the audiological
evaluation to confirm his hearing should have been completed by 5 months of age.
d. Since a hearing loss was identified, early intervention services (including fitting with
amplification) should have begun no later than 6 months of age.
Explanation: Early Hearing Detection and Intervention (EHDI) guidelines (ASHA, 2022) recommend a minimum of 1-3-6 goals. This includes:
n
hearing screening completion by 1 month of age,
n
diagnosis of any hearing loss by 3 months of age,
n
hearing aid selection and fitting within 1 month of confirmation of hearing loss, and
n
starting early intervention services by 6 months of age.
For programs able to meet the 1-3-6 goal, EHDI guidelines suggest programs consider a new target of
1-2-3. Therefore, d is the correct answer.
CHAPTER 8 Screening and Hearing Conservation
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Appendix 8–A
Comparison of the OSHA Noise Standard and
the NIOSH Noise Recommendations
OSHA NIOSH
413
Noise Exposure
Limits
Exchange Rate 5 dB 3 dB
Hazardous Exposure Above the PEL (or the equivalent) At or above the REL (or the equivalent)
Protections Feasible administrative or engineering
Ceiling Impact or impulse noise exposure
Action Level 8-hour TWA of 85 dBA or a dose of 50%
Noise Exposure
Monitoring
Noise Monitoring
Strategy
Maximum permissible exposure level
(PEL) = 90 dBA as an 8-hour timeweighted average (TWA)
controls shall be used for employees
exceeding the PEL. If these controls fail
to reduce noise exposure to the PEL or
less, hearing protection devices (HPDs)
must be worn.
should not be greater than a peak sound
pressure level (SPL) of 140 dB.
Conducted for employees with noise
exposure of 85 dBA TWA or greater
Use representative personal noise
sampling when workers move around,
noise levels vary significantly, or impulse
noise is present.
Recommended exposure level (REL) =
85 dBA as an 8-hour TWA
Feasible administrative and engineering
controls shall be used to reduce noise
exposures below the REL. Employees
must wear HPDs if their noise exposure
equals or exceeds the REL.
No noise (continuous, varying,
intermittent, or impulse) should exceed
140 dBA.
Conducted for employees with noise
exposure of 85 dBA TWA or greater
Can use a task-based exposure
monitoring strategy when workers
move around and/or noise levels vary
Types of Noise
Included
Instrumentation Calibrated sound level meter or
Repeat Noise
Measurements
Audiometric Testing Available for all employees exposed to
Audiometric Test
Personnel
All continuous, intermittent, and
impulse noise from 80 to 130 dBA
dosimeter set to slow and dBA
If there is a significant increase in noise
exposure
85 dBA TWA or greater
Audiologist, a physician, a technician
certified by the Council for
Accreditation in Occupational Hearing
Conservation (CAOHC), or an
individual with equivalent training
All continuous, varying, intermittent,
and impulse noise from 80 to 140 dBA
Calibrated sound level meter (Type 2 or
better) set to slow and dBA
At least every 2 years for workers with
an 8-hour TWA of 85 dBA or greater
Provided for all employees exposed to
85 dBA TWA or greater
Audiologist, a physician, a technician
certified by the Council for
Accreditation in Occupational Hearing
Conservation (CAOHC), or an
individual with equivalent training
continues
APPENDIX 8–A. continued
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OSHA NIOSH
Test Frequencies Air-conduction, pure-tone audiometry
at 500, 1000, 2000, 3000, 4000, and
6000 Hz
Audiometric
Equipment
Audiometers must meet ANSI
S3.6–1969.
Calibration Daily functional check, annual
acoustical check, and exhaustive
calibration every 2 years
Test Environment Test rooms must not have noise levels
(in dB SPL) greater than:
• 500 Hz = 40
•
1000 Hz = 40
• 2000 Hz = 47
• 4000 Hz = 57
• 8000 Hz = 62
Measured using at least a Type 2 sound
level meter (ANSI S1.4–1971)
Air-conduction, pure-tone audiometry
at 500, 1000, 2000, 3000, 4000, and
6000 Hz
Audiometers must meet ANSI
S3.6–1996.
Daily functional check, acoustical check
when the daily check shows a threshold
difference greater than 10 dB in either
headphone at any frequency, and
exhaustive calibration every year or when
the acoustic check indicates the need
Following ANSI S3.1–1991, test rooms
must not have noise levels (in dB SPL)
greater than:
• 125 Hz = 49
•
250 Hz = 35
• 500 Hz = 21
• 1000 Hz = 26
• 2000 Hz = 34
•
4000 Hz = 37
• 8000 Hz = 37
Measured using at least a Type 1 sound
level meter (ANSI S1.4–1983)
Baseline Audiogram Within 6 months of exposure at or
above 85 dBA TWA or 1 year if testing
using a mobile test van
Must be preceded by at least 14 hours
without workplace noise exposure (can
substitute use of hearing protection)
Annual Audiogram Performed for all employees with noise
exposure at or above 85 dBA TWA
Before employment or within 30 days
of employment for workers exposed to
85 dBA TWA or greater
Must be preceded by at least 12 hours
of quiet (cannot substitute use of
hearing protection)
Performed for all employees with noise
exposure at or above 85 dBA TWA
Referred to as the “monitoring
audiogram”
Test Scheduling Should be scheduled at the end of or
late in the work shift to detect any
temporary threshold shifts
Threshold Shift Standard threshold shift (STS) —
Average change of 10 dB or more at
2000, 3000, and 4000 Hz in either ear
compared to the baseline audiogram
Significant threshold shift — Change of
15 dB or more in either ear at any of
the following frequencies: 500, 1000,
2000, 3000, 4000, or 6000 Hz
Audiometric Retest Can retest within 30 days Can retest immediately but must retest
within 30 days
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OSHA NIOSH
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Audiogram Review Must be performed by an audiologist or
physician
Baseline Revision Annual audiogram with the STS
becomes the new baseline
Notification Employees must be notified in writing
within 21 days if an STS is detected.
Actions After a
Threshold Shift
Required actions:
Fit, train, and require the employee
•
to use hearing protection
•
Refit and retrain employees who
have previously worn hearing
protection
Refer for evaluation by an
•
audiologist or otolaryngologist if
a medical pathology of the ear is
suspected
•
Notify employees when an otologic
exam is needed for an ear problem
Must be performed by an audiologist or
physician
Annual audiogram with the significant
threshold shift becomes the new
baseline
Employees must be notified within 30
days if a significant threshold shift is
detected.
A minimum of the following
appropriate actions:
Reinstruct and refit hearing
•
protection
•
Retrain on worker responsibilities
for hearing conservation
•
Reassign to work in a quieter area
Availability of
Hearing Protection
Available to all employees exposed to
85dBA TWA or greater at no cost to
the employee
Must be replaced as needed
Use of Hearing
Protection
Must be worn by employees when:
Exposure is 90 dBA TWA or
•
greater
•
Exposure is 85 dBA TWA or
greater if no baseline audiogram
has been obtained after 6 months
of exposure at or above 85 dBA
TWA or an STS has occurred
Hearing Protection
Selection
Must allow employees to select from a
variety of appropriate options
Employee Training Must train employees in care and use of
hearing protection
Hearing Protection
Fitting
Must ensure appropriate initial fit and
supervise correct use
Must be worn by employees when noise
is 85 dBA TWA or greater
Provided at no cost to the employee
Must train employees at least annually
to select, fit, and use a variety of
appropriate hearing protectors
Hearing Protection
Attenuation
Must attenuate to at least 90 dBA (85
dBA if the employee has had an STS)
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Must attenuate to below 85 dBA TWA
continues
APPENDIX 8–A. continued
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OSHA NIOSH
Hearing Protection
Evaluation
Double Hearing
Protection
Employee
Involvement
Evaluation based on the NRR when
using the dBC or the dBA scale for
noise measurement:
Estimated Exposure (dBA) = TWA
(dBC) − NRR
Estimated Exposure (dBA) = TWA
(dBA) − (NRR – 7)
Strongly recommended correction
factor for estimating field attenuation:
Estimated Exposure (dBA) = TWA
(dBC) − [NRR × 50%]
Estimated Exposure (dBA) = TWA
(dBA) − [(NRR − 7) × 50%]
*NRRh—Represents the higher NRR
of the two types of protection
Estimated Exposure (dBA) = TWA
(dBC) − (NRRh + 5)
Estimated Exposure (dBA) = TWA
(dBA) − [(NRRh − 7) + 5]
Reevaluate when employee noise
exposure increases to the point that the
current hearing protection may not
provide sufficient attenuation
Evaluation using correction factors
applied to the NRR to estimate field
attenuation:
Earmuffs—Subtract 25% from the
NRR
Formable earplugs—Subtract 50%
from the NRR
All other earplugs—Subtract 70% from
the NRR
Should be worn by employees exposed
to greater than 100 dBA TWA
Train employees at least annually
to select, fit, and use a variety of
appropriate hearing protectors
Hearing
Conservation
Training Program
Hearing
Conservation
Training Program
Topics
Provided to employees exposed to 85
dBA TWA or greater and must ensure
participation
• Effects of noise on hearing
Purpose of HPDs, advantages,
•
disadvantages, and attenuation of
different types of HPDs
•
Instructions on selection, fitting,
use, and care of HPDs
Explanation of audiometric testing
•
Hearing
Repeated annually Repeated annually
Conservation
Training Timeframe
Recordkeeping Store all noise exposure records for at
least 2 years
Keep all audiometric test records for at
least the duration of employment
Transfer all records to the next employer
if the business is sold
Provided to employees exposed to
85dBA TWA or greater and must
ensure participation
• Effects of noise and hearing loss
• Selection, fitting, use, and care of
HPDs
•
Audiometric testing
• Roles and responsibilities of
employers and employees in
preventing NIHL
Store all noise exposure records for 30
years
Keep all audiometric test records for the
duration of employment, plus 30 years
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Audiology Review: Preparing for the Praxis and Comprehensive Examinations
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Treatment:
Topics in Amplification
Emily Jo Venskytis and Melanie Lutz
Chapter 9
Introduction to Hearing Aids
Modern hearing aid (HA) technology has progressed from basic analog amplifiers to complex digital
signal processing. Many HA styles are now available to accommodate a range of hearing loss severity,
provide increased comfort, improve accessibility and connectivity with communication devices, and
enhance cosmetic appeal. Within the casing of each HA, similar processing takes place at the fundamental level. Refer to Chapter 3 for a description and visual of digital signal processing (DSP) basics.
The term HA used in this chapter will refer to prescription hearing aids (non-over-the-counter devices)
unless otherwise noted.
Candidacy
HA candidacy is first determined by a comprehensive audiologic evaluation. If aidable hearing loss is
identified, the audiologist may proceed with amplification or make a medical referral. All pediatric
patients must be evaluated by a physician prior to a HA fitting. Requirements for when to refer adult
patients to an otolaryngologist may vary by state. Clinical findings that warrant a referral prior to
hearing aid fitting include but are not limited to:
n
The patient has an outer-ear malformation.
n
There is occluding cerumen and/or a foreign body identified in the external auditory canal
(depending upon the audiologist’s scope of practice defined by their state).
n
The patient reports, or the audiologist identifies, active ear drainage in the last 90 days.
n
There is a sudden onset of hearing loss, either unilateral or bilateral.
n
The patient reports acute or chronic dizziness.
n
The audiologic evaluation identifies significant air-bone gaps or a significant asymmetry
between ears.
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In addition to audiologic and otologic indicators, a patient-centered care approach supports the
consideration of additional personal factors to guide amplification recommendations for each patient.
These considerations include:
n
The patient’s identified needs and difficulties
n
The patient’s perspective of their activity limitations and participation restrictions
n
The patient’s level of motivation to obtain and consistently utilize amplification
n
The patient’s goals
n
The patient’s activities of daily living
HA candidacy decisions also include whether the patient should be fit monaurally (in one ear) or
binaurally (in both ears). Patients with bilateral hearing loss should normally be fit binaurally. Benefits
of binaural amplification include:
n
Loudness summation: binaural amplification provides equal access to sound at each ear, which
increases the perception of loudness.
n
Reducing negative consequences of the head shadow effect: the intensity of a sound arriving
from one side of the head is reduced when it reaches the other side of the head. Highfrequency sounds arriving at one ear may be attenuated 10 to 15 dB at the contralateral ear.
Amonaural HA fitting on a patient with bilateral hearing loss may exacerbate this effect.
n
Speech intelligibility in noise: an improvement in speech intelligibility in noise is expected
when using binaural amplification compared to monaural amplification.
n
Sound localization: localization relies on comparisons made between amplitude and time
differences of sound reaching each ear. Monaural HA fittings on a patient with bilateral
hearing loss will negatively impact their localization by distorting the interaural timing
differences and interaural level differences between ears. Binaural HA fittings should result in
improved sound localization compared to a monaural HA fitting.
AUDIOLOGY NUGGET
Although binaural amplification is typically recommended for patients with bilateral hearing loss, some individuals may have poorer speech recognition associated
with a binaural HA fitting compared to a monaural fitting. This phenomenon
is known as binaural interference, and research suggests it is present in 16.7% of
listeners (Mussoi & Bentler, 2017). Speech-in-noise tests such as the Hearing in
Noise Test (HINT) as well as monaural (right and left tested separately) versus
binaural aided word recognition testing may help the audiologist identify binaural
interference in patients with a preference for one HA rather than two.
When individuals with hearing loss forgo the implementation of amplification, they may face
negative effects on their health and well-being. Potential consequences of untreated hearing loss include:
n
Exertion of additional effort to hear and understand speech compared to normal-hearing
peers. This may result in stress, strain, and fatigue related to communication experiences
throughout their day.
CHAPTER 9 Treatment: Topics in Amplification
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n
Avoidance of the stress of communication difficulties by withdrawing from social activities.
Awithdrawal from community may lead to anxiety, loneliness, and/or depression.
n
Poor job performance and reduced earning potential
n
Decrease in alertness and environmental awareness may result in safety risks.
n
Negative effects on memory and a frequently discussed relationship with cognitive decline
AUDIOLOGY NUGGET
Untreated hearing loss is associated with cognitive decline; however, research has
yet to determine a causal link (i.e., cause-effect relationship) between the two.
At this time, it is incorrect to state that untreated hearing loss causes cognitive
decline. Additional factors related to untreated hearing loss, such as reduced
communication and isolation, must also be considered. For additional information on this topic, please refer to Slade et al. (2020) or Yeo et al. (2022).
419
The timely diagnosis of hearing loss and administration of amplification is especially crucial for
pediatric patients when the desired communication method is spoken language. The Joint Committee
on Infant Hearing (JCIH) Position Statement 2007 dictates a goal for Early Hearing Detection and
Intervention (EHDI) to maximize linguistic and literacy development for children who are deaf or
hard of hearing. Guidelines were created and are referred to as the 1, 3, 6 rule. Per the 1, 3, 6 rule,
infants should receive a newborn hearing screening by 1 month of age. If indicated, a comprehensive
diagnostic evaluation should be completed by 3 months of age. For those who qualify, early intervention services and audiologic and/or otologic management should be initiated by 6 months of age. In
2019, EHDI updated these guidelines and now recommend that those states able to meet the 1, 3, 6
rule should now meet a 1-, 2-, and 3-month timeline.
KNOWLEDGE CHECKPOINT
A patient’s chronological age is the age as determined by their date of birth. Not
all children develop in line with their chronological age. Delayed physical, intellectual, and/or social development may place a child at a younger developmental
age, compared to their chronological age. It is important to consider the patient’s
developmental age when anticipating their ability to participate in behavioral
testing or meet auditory milestones.
Hearing Aid Technology
When compared to analog HAs of the past, modern HA technology has become increasingly smaller
and electronically more sophisticated. The advent of DSP drastically improved the ability to manipulate HA settings and create a more comfortable fit with the potential for improved audibility without
feedback.
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420
Power Source
Energy is provided to HAs via disposable or rechargeable batteries.
n
Disposable batteries are typically air-activated zinc batteries, available in a range of sizes coded
by color and number. Larger batteries (i.e., 13 or 675) are used for HAs with more powerful
output capabilities and will last longer compared to smaller batteries (i.e., 10 or 312).
Battery life will depend on several things, for example, daily length of use, battery size, and
utilization of different functions in the HA (such as streaming). Battery size is also linked
to the lifespan of the battery: Larger batteries (10–14 days) last longer than smaller batteries
(4–10 days). More wireless (streaming) usage will reduce the battery life.
n
Rechargeable HAs are typically equipped with lithium ion (Li-Ion) batteries. It is
recommended that a rechargeable HA is placed on the manufacturer-specific charger each
night to ensure a full day of HA use.
Transducers and Amplifiers
Regardless of HA style, the internal components remain relatively the same. Two essential internal
components are transducers and amplifiers.
n
A transducer converts one type of energy to a different type of energy. The pathway of sound
traveling through a DSP HA requires multiple energy conversions.
n
Transducers in modern HAs include the microphone, the receiver, and the telecoil.
The microphone converts acoustic signals to electric signals (i.e., analog to digital signals).
The telecoil converts electromagnetic signals to electric signals.
The receiver converts the electric signal to an acoustic signal.
n
The amplifier provides gain to incoming acoustic signals. Electric input waveforms are
digitized then converted back to analog.
Gain of a HA is sound or additional “volume” added to the incoming signal. ANSI (2014)
defined gain as the difference between the output and input sound pressure level (SPL) in a
coupler. This numerical value is expressed in decibels (dB).
Output of a HA is the total sound produced by the HA. This numerical value is expressed
as dB SPL.
Gain and Amplitude Compression
HAs can operate in linear and nonlinear ways. The term linear refers to changes in output that coincide
with equal changes in input (as input increases by 10 dB, output increases by 10 dB). Nonlinear refers
to changes in output that do not coincide with equal changes in input (as input increases by 10 dB,
output increases by 5 dB). In this case, there is a 2:1 relationship, which is referred to as the compression ratio (CR).
n
This relationship can be viewed in Figure 9–1 wherein the dashed line shows an increase in
input (along the x-axis) from 20 to 40 dB (change of 20) equaling a change in output (along
the y-axis) from 60 to 80 dB (change of 20). This represents a linear input/output function.
Now view the change in input from 40 to 60 dB (change in 20) and the corresponding
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FIGURE 9 –1. Graphical representation of compression and expansion. This image conceptualizes
the input to output of compression and expansion as compared to a linear (1:1) input-output
function.
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change in output from 80 to 90 dB (change in 10). This is a nonlinear input/output function
demonstrating nonlinearity or compression (specifically a CR of 2:1).
n
The compression knee point (TK) is the point at which compression is activated (gain
is reduced) and the input/output becomes nonlinear. Gain is linear below this point and
nonlinear above this point (as shown in Figure 9–1). The TK is often described by being either
high or low based on the specific compression application.
n
A high TK is typically ≥85 dB SPL, meaning gain will not be reduced until the incoming
signal reaches 85 dB SPL. The decision to implement a high TK may be made to maximize
listening comfort by limiting the output of the HA but limiting the compression (gain
reduction) of average conversational speech (approximately 65–70 dB SPL).
n
A low TK describes a TK <50 dB SPL. A low TK may be used to increase the audibility of
soft sounds but reduces gain for conversational speech levels, which can have deleterious
consequences for speech recognition. In these cases, increasing the TK allows for more linear
processing of conversational level speech and potential improvements in speech understanding.
HA compression can be categorized as input (AGC-I) or output compression (AGC-O). See
Table 9–1 for distinctions between these types of compression. The time it takes for HA compression
to activate and deactivate is also variable and directly impacts sound quality and signal integrity. These
factors are known as the attack time (AT) and release time (RT).
n
AT is the time elapsed between the onset of a sound at or above the TK and the adjustment to
reduce gain.
n
RT is the time between the cessation of the sound that activated compression (and reduced
gain) and the return of HA gain to precompression levels.
Adaptive RTs reduce distortion by automatically changing the RT depending on the length of
the compression activating signal. The use of fast ATs and RTs may be useful in providing improved
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