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SYMPTOMS LESION SITE
AUDITORY
SYMPTOMS
Labyrinth
Preceded by
barotrauma,
tinnitus
head trauma,
middle ear surgery
(stapedectomy),
Valsalva maneuver;
None
nausea; vomiting
None Preceded by acute/
episodic vestibular
syndromes, neurologic,
psychological, or other
illnesses
Labyrinth
Autophony; sensitive
to loud sounds or
pressure in ear;
oscillopsia; drop
attacks
Low-frequency
conductive hearing
loss; normal
immittance;
tinnitus; may
report amplification
of sound
leading to
None Possible oscillopsia Neural/vascular
labyrinthine
damage
Vestibular
Brun’s nystagmus;
Unilateral hearing
portion on CN
VIII; possible
labyrinth,
brainstem, or
cerebellum
hemifacial numbness/
weakness
loss, unilateral
tinnitus
NUMBER
VESTIBULAR
OF ATTACKS PROVOCATION
Multiple Pressure changes Hearing loss;
Seconds to
SYMPTOMS DURATION
minutes
imbalance/
unsteadiness;
vertigo
Motion; upright
posture; moving/
complex visual
stimuli
Constant/
multiple
Constant
for days
(>3months)
Dizziness;
unsteadiness
pressure changes
Multiple Loud noise;
Lasts as long
as the sound
(30–60
seconds); can
Episodic vertigo
following loud
sounds
be longer
preceded by
illness; often
idiopathic
Single Sometimes
30 minutes to
days
Rotational
vertigo
Not usually
provoked
(multiple)
Constant Constant
Gradual
imbalance or
dizziness
APPENDIX 2–E. continued
DIAGNOSIS
Perilymph fistula Dizziness;
Persistent
postural-
perceptual
dizziness
82
Superior
semicircular
canal dehiscence
(SSCD)
Vestibular
neuritis
Vestibular
schwannoma
CHAPTER 2 Anatomy, Physiology, and Relevant Pathologies
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Appendix 2–F
Genetic Disorders and Syndromes
DISORDER/
SYNDROME INHERITANCE PATTERN IDENTIFIERS AUDITORY FINDINGS
83
Achondroplasia Autosomal dominant Form of short-limbed
dwarfism
Enlarged heart
Depressed nasal bridge
Short, stubby hands
Lordotic lumbar spine
Protruding abdomen
Alport syndrome Primarily X-linked,
but can be autosomal
recessive or dominant
Apert syndrome Autosomal dominant Fused fingers and toes
AUNA1 Autosomal dominant Nonsyndromic ANSD with late teen
Males more affected
Abnormal retina color
Kidney abnormalities
(glomerulonephritis)
(syndactyly)
Possible stenosis or
atresia
Ear infections
CHL or SNHL
SNHL, progressive
Bilateral flat CHL; can
be SNHL
onset
Progress to profound
CHARGE Autosomal dominant Ocular abnormality
(coloboma)
Heart defects
Abnormal nasal structure
(atresia chonae)
Delayed growth and
puberty
Genital abnormalities
Congenital unilateral
lower lip palsy
(CULLP)
Connexin 26 (GJB2) Autosomal dominant;
Autosomal dominant
Also due to birth trauma
(compression of nerves)
can be autosomal
recessive
Unilateral facial paralysis
seen when baby cries
Nonsyndromic Progressive bilateral
SNHL or MHL
Possible SNHL
SNHL
continues
Audiology Review: Preparing for the Praxis and Comprehensive Examinations
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84
APPENDIX 2–F. continued
DISORDER/
SYNDROME INHERITANCE PATTERN IDENTIFIERS AUDITORY FINDINGS
Connexin 30 (GJB6) Autosomal dominant;
can be autosomal
recessive
Connexin 31 (GJB3) Autosomal dominant Nonsyndromic
Nonsyndromic Progressive high-
frequency SNHL with
adolescent onset
Bilateral SNHL
Can occur with
peripheral neuropathy
DFNA1 Autosomal dominant Nonsyndromic Low-frequency SNHL
progressing to flat severe
SNHL
May have vestibular
symptoms
DFNA2A Autosomal dominant Nonsyndromic Tinnitus in some
Progressive highfrequency SNHL
DFNA5 Autosomal dominant Nonsyndromic Progressive high-
frequency SNHL that
moves to mid- and low
frequencies
Onset between 11 and
50 years
DFNA6/14/38 Autosomal dominant Nonsyndromic Low-frequency SNHL
Progressive
Tinnitus in some
DFNA8/12 Autosomal dominant Nonsyndromic Mid-frequency SNHL
HL is stable or
progressive
DFNA13 Autosomal dominant Nonsyndromic Mid-frequency SNHL
(cookie bite)
Stable
Possible tinnitus
DFNB4 Autosomal recessive Nonsyndromic Inner ear malformations
Fluctuating and/or
progressive SNHL
Vestibular anomalies
DFNB9 Autosomal recessive Nonsyndromic Mid-frequency SNHL
(cookie bite) or ANSD
CHAPTER 2 Anatomy, Physiology, and Relevant Pathologies
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DISORDER/
SYNDROME INHERITANCE PATTERN IDENTIFIERS AUDITORY FINDINGS
DFNB21 Autosomal recessive Nonsyndromic Severe to profound
mid-frequency SNHL
85
DFNX2 X-linked Nonsyndromic Males:
deformity; progressive
MHL
Females:
DFNX4 X-linked Nonsyndromic Males:
frequency SNHL (onset
3–7 years)
Females:
(onset childhood–40s)
Jervell &
Lange-Nielsen
Autosomal recessive Prolonged heart QT
interval
Bilateral profound
SNHL
Repeated syncope attacks
Seizures
MTRNR1 &
MTTS1
Mitochondrial Nonsyndromic Causes enhanced
susceptibility to
aminoglycoside
ototoxicity (progress to
profound SNHL)
Possible constant tinnitus
Temporal bone
Possible mild HL
Progressive high-
Possible HL
Noonan syndrome Autosomal dominant Short stature
Widely spaced eyes
(usually pale blue or
Middle and inner ear
anomalies
CHL, MHL, SNHL
green)
High-arched palate
Downward palpebral
fissures
Short nose
Broad or webbed neck
Hypotonia
Cardiac anomalies
Normal intelligence
Pendred syndrome Autosomal recessive Goiter (enlarged thyroid) Bilateral high-frequency
SNHL, progressive
Enlarged vestibular
aqueducts
Possible vestibular
anomalies
continues
Audiology Review: Preparing for the Praxis and Comprehensive Examinations
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APPENDIX 2–F. continued
DISORDER/
SYNDROME INHERITANCE PATTERN IDENTIFIERS AUDITORY FINDINGS
Stickler syndrome Autosomal dominant Flat facial profile
Mandibular hypoplasia
Cleft palate
Musculoskeletal and
joint issues
Joint hypermobility
Osteoarthritis
Long limbs
Slender bones
Nearsighted
Retinal detachment
Cataracts
Blindness
Treacher Collins
syndrome
Autosomal dominant or
recessive
Craniofacial
abnormalities
Pinna deformities
Usher syndrome
Type I — age 10
Autosomal recessive Retinitis pigmentosa
(progressive eye disease)
Type II — early 20s
Type III — puberty
Type 1 — high-frequency
SNHL
— severe and
Type 2
progressive SNHL
Type 3
— mild to
moderate SNHL
Primarily CHL, can be
MHL or SNHL
Bilateral SNHL
(progressive
— Types I
& III)
Dizziness and/or
imbalance
Waardenburg
syndrome
Autosomal dominant
(Types I & II)
Autosomal recessive
(Types III & IV)
White forelock
Upper limb
abnormalities (Type III)
Hirschprung disease
(Type IV)
Dystopia canthorum
(wide nasal bridge)
Synophrys (unibrow)
Heterochromia (Type II)
Musculoskeletal
(TypeIII)
SNHL, nonprogressive
Vestibular dysfunction
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Acoustics, Psychoacoustics,
and Instrumentation
Jenna Cramer, Katharine Fitzharris, and Jeremy J. Donai
Principles of Sound
Chapter 3
Three attributes commonly used to characterize sound (including speech) are frequency, amplitude,
and phase. Each of the three contribute to the accurate perception of speech and other auditory signals
in different ways.
Frequency
n
Frequency is the number of complete cycles that occur during a specified amount of time,
usually 1 second, measured in hertz (Hz). Frequency of a sound is described in terms of its
fundamental, or lowest frequency, and formants (natural resonances of the vocal tract in the
case of speech) or harmonics (integer multiple of the fundamental), which are successively
higher frequencies that help distinguish sounds (e.g., phonemes) from one another.
n
The perceptual correlate of frequency is pitch, which is defined as an attribute of auditory
sensation in which a sound may be ordered on a scale extending from low to high. Biological
male voices are often characterized as having a low pitch (with fundamental frequencies
between 100 and 175 Hz) and biological female voices as having a relatively higher pitch (with
fundamental frequencies between 200 and 300 Hz).
Amplitude
Amplitude refers to the maximum displacement of the particles of a medium, measured in decibels
(dB). Perceptually, it is related to the magnitude (e.g., loudness) of a signal.
n
Peak Amplitude
Peak amplitude refers to the maximum positive or negative deviation of a sound from
its zero-reference level or baseline. For an undamped pure tone, this value remains
constant throughout the signal. For complex signals such as speech, peak amplitude varies
throughout the signal.
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n
Peak-to-Peak Amplitude
Amplitude measurements that are made from the point of maximum displacement in one
direction to the point of maximum displacement in the other direction. This value can
be informative for tonal signals that repeat consistently over time but is less helpful for
measuring the amplitude of more complex signals such as music or speech.
n
Root Mean Square (RMS) Amplitude
Root mean square (RMS) amplitude of a signal can provide valuable information about
the average signal strength across the entire signal. Calculating RMS amplitude involves
(1)squaring the amplitude values over the length of the signal, (2) calculating the average
of all amplitude values, and (3) finding the square root of the average.
RMS amplitude values are helpful when determining the amplitude of complex signals such
as music or speech. Because natural speech signals fluctuate in amplitude from moment
to moment and the waveform does not consistently repeat, using a value such as peak or
peak-to-peak amplitude is not recommended, as it often does not provide an amplitude
value representative of the entire signal. For these types of signals, RMS amplitude values
are more informative and commonly measured.
Phase
Phase represents the point in a cycle at which a vibrating object is located at a given instant in time.
Phase is often described as a location or degree of radians of a circle. The topic of phase has significant
implications for clinical and research activities performed by audiologists and hearing scientists.
n
One example relates to the phase of a signal (i.e., condensation vs. rarefaction) and auditory
system stimulation. Recall that the rarefaction phase of a signal leads to depolarization
(increased firing) of the neural system due to an upward movement of the basilar membrane,
movement of the hair cells toward the modiolus, shearing of the stereocilia toward the stria
vascularis, opening of the mechanically gated channels, and release of the neurotransmitter
glutamate.
n
Conversely, the condensation phase leads to hyperpolarization (reduced firing) of the neural
system due to a downward movement of the basilar membrane, movement of the hair cells
toward the stria vascularis (lateral wall), shearing of the stereocilia toward the modiolus, and
a compression of the mechanically gated channels (see Musiek & Baran, 2020, for additional
information).
n
Clinically, signal phase influences the latency of waves during the auditory brainstem response
(ABR) evaluation in that the rarefaction phase will elicit waves with shorter latencies due to
depolarization occurring during rarefaction phase.
Phase Cancellation
Phase cancellation, also commonly referred to as phase inversion, is a popular technique used to reduce
acoustic feedback in hearing aids.
n
When feedback is detected by a hearing aid, a signal of the same frequency that is 180° out of
phase with the feedback signal is used to create a cancellation effect and reduce feedback.
CHAPTER 3 Acoustics, Psychoacoustics, and Instrumentation
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Q & A
Question: When conducting a pure-tone threshold evaluation in the audiology
clinic using audiometric earphones, does signal phase affect hearing thresholds
in the ear being tested?
Answer: No, phase does not affect the perception of a signal when presented
monaurally. Phase becomes increasingly important when conducting binaural
testing (because phase is important when listening with both ears, as in the
Masking Level Difference [MLD] test). In other words, the phase of a sine wave
is irrelevant when testing one ear at a time, as is done in a traditional audiological
evaluation. However, phase differences can enhance the detection of a signal
when presented binaurally and out of phase. It is thought that the superior
olivary complex (SOC) is primarily responsible (at least early in auditory perception) for detecting and processing these phase differences in terms of the
interaural timing difference (ITD) or interaural phase difference (IPD) used for
localization.
89
Lead and Lag
Most surfaces reflect sounds and influence the acoustic environment of a room. When an auditory
signal is present, a listener hears both the initial and reflected signal. Sound coming from an initial
source arrives at the ears first (lead). The echo, or reflected sound, subsequently arrives at the
ears (lag).
n
In Figure 3–1, the solid gray line leads the black dashed line by 90°. The starting phase of the
solid line is 90°, and the starting phase of the dashed line is 0°. It should be noted that the
current visual is an example of one reflected signal. In reality, additional reflections would
occur in a typical acoustic environment.
FIGURE 3–1. Example of lead and lag.
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AUDIOLOGY NUGGET
Recall that in the traditional soundfield set up in the audiology clinic, the use of
pure-tone signals to measure hearing sensitivity is not advisable due to the possibility of reduced signal amplitude in locations within the testing area resulting
from standing waves. Standing waves result when signal reflections interact with
an original signal in the same location with a 180° phase difference. Amore
complex signal such as a warbled or frequency modulated (FM) tone or narrowband noise to avoid this deleterious phase interaction is recommended in
these situations.
Precedence Effect
In reverberant environments, sounds reach the ears through several paths. Although the direct sound
is followed by multiple reflections, which would be audible in isolation, the first-arriving (lead) sound
dominates many aspects of auditory perception. The precedence effect refers to a phenomenon that is
thought to be involved in resolving competition for perception and localization between a direct sound
and subsequent sound reflections.
n
In binaural hearing, a slightly delayed signal is not entirely ignored but may influence
the precise localization of the sound source. Because of the precedence effect, echoes and
reverberated sounds are minimized for a short period after the original sound.
Q & A
Question: An educational audiologist is tasked with determining the reverberation time of a classroom to provide a rationale for ear-level versus soundfield FM
systems for students with hearing loss. What guidelines would they use for their
measurement?
Answer: ANSI S12.60: ANSI Standard for Classroom Acoustics specifies that
classrooms less than 10,000 cubic feet have RT60 (time it takes from sound
cessation to decay by 60 dB) values of ≤0.6 second and ambient noise levels
≤35dBA.
Digital Signal Processing (DSP)
Digital signal processing (DSP) involves creating a digital code (0s and 1s) from an auditory signal.
This requires taking amplitude measurements of a continuous signal at discrete points in time. DSP
is routinely used in consumer products such as cell phones, personal tablets, televisions, and most
clinical/research equipment used by speech and hearing professionals, including hearing aids (HAs)
and cochlear implants (CIs).
CHAPTER 3 Acoustics, Psychoacoustics, and Instrumentation
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n
Two important factors in this process are accurately capturing the amplitude of the signal
91
(amplitude quantization or amplitude resolution) and the rate at which the process occurs
(sampling frequency). In simpler terms, these two processes are related to how accurately and
how quickly the analog signal is sampled to reduce error and preserve the original signal to the
highest degree possible.
Amplitude Resolution and Sampling Frequency
One important factor in DSP is accurately capturing the amplitude of the signal through a process
called amplitude quantization. The other is the rate at which this process occurs, often referred to as
sampling frequency or sample rate.
n
Amplitude quantization refers to the process of using binary numbers (0s and 1s) to represent
the amplitude of a signal. The term bit refers to the size of the series of 0s and 1s used to
x
describe the amplitude of a signal. This is commonly displayed at 2
(x) representing the number of bits. As such, a 4-bit system (2
combinations of 0s and 1s to represent amplitude values. Please refer to Figure 3–2 for an
example of a 2- and 4-bit system. Sixteen-bit (65,535 potential amplitude values) is the most
often used value; however, 24- and 32-bit are also available.
Each bit provides for approximately 6 dB in dynamic range for a digital system. Thus,
a 16-bit system (commonly used in audio applications) has a 96 dB dynamic range
(16 × 6 = 96).
n
Sampling frequency or sample rate refers to the number of times per second amplitude
quantization occurs. Thus, with a sampling frequency of 44.1 kHz (or 44,100 Hz), the
amplitude of the continuous signal is quantified 44,100 times per second, creating 44,100
discrete numerical values.
, with the exponent
4
) allows for 16 potential
FIGURE 3–2. Visual representation of amplitude resolution. Source: Adapted from Hearing Science Fun-
damentals, Second Edition (pp. 1–370) by Lass, N. J., & Donai, J. J. Copyright © 2023 Plural Publishing, Inc.
All rights reserved.
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