Decreased sound tolerance in autism: Understanding and distinguishing between hyperacusis, misophonia, and phonophobia

Abstract

Decreased sound tolerance (DST) affects a significant proportion of autistic people throughout their lifetime and, as Zachary J Williams explains, it is important that clinicians are aware of the three distinct subtypes of DST when making a diagnosis. This article also includes operational diagnostic criteria and suggested billing codes for each of the three DST syndromes described in the article, which may be applied to both autistic and non-autistic individuals.

Full text

AUDIOLOGY FEATURE
Autism spectrum disorder
(hereaer ‘autism’) is a
heterogeneous, lifelong
neurodevelopmental condition
characterised by diculties with social
communication, repetitive behaviours,
and atypical reactions to sensory aspects
of the environment. Notably, an estimated
50-70% of autistic individuals demonstrate
clinically signicant decreased sound
tolerance (DST, i.e. an inability to tolerate
everyday sounds) at some point in their lives
[1], oen resulting in referrals of autistic
children and adults to audiologists or
other hearing health professionals. As DST
in autism appears to represent multiple
distinct yet oen overlapping syndromes
[2] (i.e. hyperacusis, misophonia, and
phonophobia), it is extremely important
that clinicians be aware of the dierences
between these conditions and feel
comfortable distinguishing between them
when making a diagnosis.
Hyperacusis (Figure 1) is a hearing
disorder in which sound of moderate
intensity is perceived as excessively
loud, painful, and/or overwhelming [2].
Individuals with hyperacusis perceive
everyday sounds, such as the sounds of
domestic appliances or electric hand driers,
as uncomfortably loud or, in some cases,
physically painful. Though frequently
associated with tinnitus and peripheral
hearing loss in the general population,
hyperacusis in autism is thought to be
neurodevelopmental in nature [2], and
additional signs of peripheral auditory
damage are frequently absent in this
population. As in cases of hyperacusis not
associated with autism, audiometric testing
of uncomfortable loudness levels can
support the diagnosis, although this test is
typically only appropriate in adolescents
and adults without signicant cognitive or
language impairment. While there is no
consensus among professionals regarding
the specic criteria used to make a clinical
diagnosis of hyperacusis, operational
criteria used by my research group to dene
hyperacusis are presented in Figure 1 to
assist clinicians in making this diagnosis.
Misophonia (Figure 2) is a newly-
described condition in which individuals
have excessive and inappropriate emotional
responses to specic ‘trigger’ sounds
(e.g. chewing, tapping, and sniing),
even when those sounds are not loud
[2]. Anger, extreme irritation, disgust, and
anxiety are the most common emotions,
though some individuals may experience
rage [3]. Misophonic triggers may evoke
a ‘ght or ight’ response, including
nonspecic physical symptoms such as
muscle tension, increased heartrate,
and sweating. Unlike in hyperacusis,
in which the acoustic properties of a
sound (i.e. intensity, frequency, and
duration) strongly predict that sound’s
aversiveness, misophonic reactions are
heavily context-dependent and may be
diminished or absent if individuals with
misophonia make the triggering sound(s)
themselves [4]. Furthermore, despite large
individual dierences in specic trigger
noises, reactions to those trigger noises,
and degree of context-dependence, the
majority of individuals with misophonia
Decreased sound tolerance in autism:
understanding and distinguishing between
hyperacusis, misophonia, and phonophobia
BY ZACHARY J WILLIAMS
Decreased sound tolerance (DST) aects a signicant proportion of autistic people
throughout their lifetime and, as Zachary J Williams explains, it is important that
clinicians are aware of the three distinct subtypes of DST when making a diagnosis.
“Though frequently
associated with tinnitus
and peripheral hearing
loss in the general
population, hyperacusis
in autism is thought to be
neurodevelopmental in
nature”
ENT & Audiology News |
MAY/JUNE 
|
VOL  NO 
| www.entandaudiologynews.com

AUDIOLOGY FEATURE
report that they are triggered at least to
some degree by oro-nasal or throat sounds
(e.g. chewing, crunching, sniing, slurping,
breathing, coughing, or throat-clearing). A
recent expert consensus paper proposed
a denition of misophonia for use in
clinical and research settings, although
concrete diagnostic criteria were not
specied [3]. To further support clinicians
in making a diagnosis of misophonia,
operational research criteria (adapted
from the consensus denition [3] and the
earlier ‘Revised Amsterdam Criteria’ for
misophonia [4]) are provided in Figure 2.
Although the word ‘phonophobia’ has
been used to refer to multiple symptoms
and conditions within the medical literature
(e.g. hyperacusis, episodic DST associated
with headaches, and loudness disturbance
due to facial nerve damage) the term
here is used to refer to a marked fear or
anxiety about specic sounds or situations
in which a person might encounter
unpleasant sounds [2]. In other words,
phonophobia refers to a specic phobia
of sound, as dened within the Diagnostic
and Statistical Manual of Mental Disorders,
Fih Edition (DSM-5) [5] and its upcoming
text revision (Figure 3). Phonophobia can
be circumscribed to very specic sounds
or generalised to all sounds with specic
qualities (e.g. loud sounds, high-pitched
sounds, sudden/unexpected sounds, or
sounds associated with a feared object/
situation). However, in all cases, the
diagnosis is only appropriate if the phobic
sound/situation almost always provokes
fear and/or anxiety and this fear/anxiety is
out of proportion to the danger posed by the
specic object/situation.
“Although hyperacusis,
misophonia, and
phonophobia are all
present in the autistic
population, there is a
notable lack of evidence-
based options for diagnosis
and treatment of these
prevalent and impairing
conditions”
Figure 1. Operational Diagnostic Criteria for Hyperacusis. These criteria are used in an ongoing research study at Vanderbilt
University Medical Center to standardise the clinical diagnosis of hyperacusis. Criteria A–E must all be met for a diagnosis to be
given. This diagnosis of hyperacusis subsumes both “loudness hyperacusis” (criterion A1) and “pain hyperacusis” (criterion A2),
particularly given the unclear distinction between the two subtypes in terms of underlying pathophysiology. For billing purposes,
ICD-10-CM code H93.233 (“Hyperacusis, bilateral”) can be used.
Figure 2. Operational Diagnostic Criteria for Misophonia. Criteria are modied from the 2020 Revised Amsterdam Criteria [4],
incorporating information from the 2021 consensus denition of misophonia [3]. Criteria A–F must all be met for a diagnosis to be
given. These criteria dier from the Revised Amsterdam Criteria insofar as (a) oro-nasal sounds are not required for diagnosis and
(b) misophonia can be diagnosed regardless of other psychiatric or neurodevelopmental conditions, provided that all diagnostic
criteria are met. Although misophonia is not formally recognised within systems of medical billing, we suggest that the diagnosis
be captured under the ICD-10-CM code H93.299 (“Other abnormal auditory perceptions, unspecied ear”).
ENT & Audiology News |
MAY/JUNE 
|
VOL  NO 
| www.entandaudiologynews.com

AUTHOR
Zachary J Williams, BS,
MD/PhD Candidate, Vanderbilt University Medical
Center, Department of Hearing and Speech Sciences,
Nashville, Tennessee, USA.
E: zachary.j.williams@vanderbilt.edu
Twitter: @QuantPsychiatry
https://www.researchgate.net/prole/Zachary-
Williams-6
Declaration of competing interests: ZJW has
received consulting fees from Roche and Autism Speaks
on projects related to autism.
AUDIOLOGY FEATURE
Notably, phonophobia can develop
secondary to other DST conditions such
as hyperacusis or misophonia. However,
in cases where feared sounds result in
signicant pain, auditory discomfort, or
other physical symptoms, an additional
diagnosis of phonophobia should be
reserved for individuals who experience
fear and anxiety to a much greater degree
than would be expected for an individual
with their same level of hyperacusis/
misophonia symptoms. In particularly
severe cases of hyperacusis, in which
certain sounds may cause extreme pain that
persists for multiple days aer exposure,
fear and avoidance of the aversive sounds
is arguably not excessive or irrational, and
phonophobia should only be diagnosed if an
individual demonstrates the same marked
fear of sounds that are not known to greatly
exacerbate their hyperacusis symptoms.
Although hyperacusis, misophonia, and
phonophobia are all present in the autistic
population, there is a notable lack of
evidence-based options for diagnosis and
treatment of these prevalent and impairing
conditions, particularly in young children
and individuals with signicant cognitive
or language impairments. Nevertheless,
even with limited access to a patient’s
internal experiences, knowledgeable
clinicians may be able to make a clear
distinction between dierent subtypes
of DST based on consideration of the
sounds the patient nds aversive, the
degree to which context modulates their
reactions, and the presence of observable
fear or anxiety in certain situations (see
Figures 1-3). With regards to management,
strategies should be individualised to
the patient’s and family’s needs and can
include modalities such as behavioural or
cognitive-behavioural therapy (oen with
an exposure/habituation component),
occupational therapy, sound generators,
amplication, medications, use of ear
protection in certain situations, and
environmental modications. Though
there is insucient evidence to strongly
support any of these interventions for DST
in autism, the treatment of this common
symptom remains an area of great clinical
need. Thus, additional basic and clinical
research is desperately needed on DST in
autism and other populations to improve
the lives of the millions of individuals who
experience these oen-disabling sound
sensitivity syndromes..
References
1. Williams ZJ, Suzman E, Woynaroski TG. Prevalence of
decreased sound tolerance (hyperacusis) in individuals
with autism spectrum disorder: A meta-analysis. Ear
Hear 2021;42(5):1137-50.
2. Williams ZJ, He JL, Cascio CJ, Woynaroski TG. A review
of decreased sound tolerance in autism: Denitions,
phenomenology, and potential mechanisms. Neurosci
Biobehav Rev 2021;121:1-17.
3. Swedo SE, Baguley DM, Denys D, Dixon LJ, et al.
Consensus Denition of Misophonia: A Delphi Study.
Frontiers in Neuroscience 2022;16:841816. https://doi.
org/10.3389/fnins.2022.841816.
4. Jager I, de Koning P, Bost T, et al. Misophonia:
Phenomenology, comorbidity and demographics
in a large sample. Doering S, ed. PLOS One
2020;15(4):e0231390.
5. American Psychiatric Association. Diagnostic and
Statistical Manual of Mental Disorders (DSM-5®). 5th ed.
American Psychiatric Association Publishing; 2013.
Figure 3. Operational Diagnostic Criteria for Phonophobia. Criteria are slightly modied from the DSM-5 criteria for specic
phobia [5], with additional information regarding the qualier of fear out of proportion to the circumstances and the ability for ear
protection use to qualify for the “avoidance” criterion. Note that for billing purposes, phonophobia should be coded using ICD-10-
CM code F40.298 (“Other specied phobia”).
ENT & Audiology News |
MAY/JUNE 
|
VOL  NO 
| www.entandaudiologynews.com