Although I have already briefly explained what misophonia and phonophobia consist of in Basic Concepts of Hyperacusis, the importance of these auditory disorders in conjunction with hyperacusis can be such that it is worth delving deeper into them.
Among the different auditory disorders in which the patient shows sound intolerance, misophonia and phonophobia are those in which, according to Dr. Jonathan Hazell, “the auditory pathways may function normally, but there is a strong abnormal reaction of the limbic system and the autonomic nervous system, to which the auditory system is closely connected.” Thus, unlike hyperacusis or recruitment, where there is a physiological problem, misophonia and phonophobia are psychological disorders caused by previous negative experiences with certain sounds. However, in the case of misophonia, not all cases are attributed to negative experiences with sounds. Some specialists, such as neuroscientist Aage R. Moller, consider that this condition is not learned but innate, and responds to some “physiological anomaly” in the areas of the brain activated by sound processing. On the other hand, audiologist Marsha Johnson points out that there seems to be a genetic component, as often members of the same family share this problem.
Unlike hyperacusis, in misophonia and phonophobia, sound intolerance occurs only with specific sounds—specifically those with which a negative association exists—and is independent of the sound’s intensity. Therefore, other sounds that are associated with pleasure, such as our favorite music, can be tolerated at much higher intensities.
Although misophonia and phonophobia are independent of hyperacusis, they often appear alongside it to varying degrees, especially in cases of severe hyperacusis. This is unsurprising given the enormous number of everyday sounds that people with hyperacusis face daily, which can threaten to make them relapse, lose progress, or cause pain. When they occur together, it is often not easy to distinguish or detect their presence. For example, the irrational fear exhibited by someone with phonophobia may be misunderstood by someone whose fear of relapse is not irrational. If there is a difference in intensity between the sounds that are uncomfortable, it is very likely that some degree of misophonia exists alongside hyperacusis. Since misophonia/phonophobia requires a different treatment from hyperacusis and can seriously hinder recovery, detecting the possible presence of these disorders is very important.
Misophonia is a term coined by neuroscientists Jawel and Margaret Jastreboff in 2001 to distinguish between the different types of sound intolerance they detected. On the other hand, Marsha Johnson used the term Selective Sound Sensitivity Syndrome (4S) to describe very similar cases, perhaps more referring to those in which a genetic component seems to be the cause. Although both terms are used to refer to practically the same condition, misophonia is the more widely used term. In any case, it is a recent condition that has been little studied, and much remains to be learned.
Everyday sounds that people with misophonia cannot tolerate when produced by others include chewing gum, chewing, breathing, pronouncing certain consonants such as p/s/k, swallowing, coughing, nasal sounds, repetitive sounds with certain objects, high heels, or dog barking, among others. In response to these sounds, those suffering from misophonia experience emotional reactions such as discomfort, anger, rage, anxiety, or even hatred or aggression. As with hyperacusis, most affected individuals hear perfectly, sometimes even better than average.
Misophonia, at least the form that supposedly has a genetic origin, has no cure to date. Treatments being carried out to alleviate its symptoms include cognitive-behavioral therapy or the use of sound generators to mask problematic sounds, which are usually of low intensity. People with misophonia sometimes use hearing protection or leave the area to avoid continuing to hear problematic sounds. If misophonia is linked to hyperacusis, a specific sound therapy using music that helps replace the negative emotional response with a positive one can be useful.
Phonophobia, as the name suggests, is a fear or aversion to exposure to loud sounds (or perceived as loud if hyperacusis is present). Exposure to these sounds can cause anxiety, heavy breathing, or panic attacks. Phonophobia is also seen as an extreme form of misophonia. When phonophobia arises from hyperacusis, the fear may be related to the concern of causing damage to the inner ear, even though most feared sounds are harmless in that regard. The fear also arises from the pain they may cause in the ears and especially from the fear of relapse.
People with phonophobia develop hypervigilance toward anything that could produce a loud sound, evaluating everything in terms of the intensity of the sound it may produce, and anticipating or avoiding every situation considered dangerous. This attitude, together with the impossibility of controlling all the sounds to which they are exposed, leads to anxiety, sometimes even at the mere thought of exposure to a sound considered dangerous.
Both misophonia and phonophobia often greatly influence the lives of those who suffer from them, as they begin to avoid places where they know they will encounter intolerable sounds. These disorders can destroy personal relationships, eliminate social activity, or cause loss of employment. It is also common for people with misophonia/phonophobia to feel misunderstood and helpless, as the low prevalence and lack of awareness of these disorders lead others to label them as overly sensitive or hysterical, deepening their suffering.
Treatment options for phonophobia are the same as those for misophonia, except for the use of sound generators. Initially, the use of anxiolytics/antidepressants may be appropriate to help reduce the anxiety it causes. It can also be very helpful to understand the mechanism by which emotions can cause these disorders and how they can make certain sounds seem louder than they actually are.
Mechanisms of Misophonia and Phonophobia
Dr. Jonathan Hazell explains in his article Decreased Sound Tolerance – Hypersensitivity of Hearing the mechanisms involved in the onset of misophonia and phonophobia, which I will summarize below.
The central processing of sound in the brain is where neurosensory information from the cochlea in the inner ear is processed, and it is located in the temporal lobe of the brain. It is there, in the auditory cortex, that conscious listening occurs. But before the sound reaches the conscious part, it passes through the subconscious, where sound patterns are classified and prepared before being relayed to the conscious part.
The central auditory system prioritizes listening to messages considered important among a lot of background noise. A typical example is when we are able to recognize a distant, weak voice saying our name amidst a crowd of people and conversations while simultaneously focusing on our own conversation. This is possible thanks to the subconscious part of the central auditory system, in which auditory signals can be enhanced or suppressed based on their meaning and on previously learned experiences. We do not consciously hear anything until it matches a sound pattern stored in our auditory memory. The strength of that match determines the loudness (perceived volume) of a particular sound, which may differ significantly from the actual intensity of that sound.
As already mentioned, in misophonia and phonophobia there is a strong link between the auditory pathways and the limbic system and autonomic nervous system. This link is responsible for emotional responses of discomfort, anger, fear, etc., to certain sounds. Once negative experiences or incorrect beliefs about the sound are learned, the limbic/autonomic system responds to the subconscious part of the auditory system, programming itself to provide an appropriate response upon future exposure to those sounds. This “appropriate” response results in an astonishing ability to detect sounds experienced as negative (even if very low), in the emotional and physiological response caused by the limbic/autonomic system, and in reinforced processing of these and other sounds, leading to hyperacusis. The purpose of this is to facilitate the detection of potential threats; it is, in fact, a natural defense mechanism.
Furthermore, any change in emotional state, specifically mood or anxiety changes, can enhance this ability to detect threats in our environment, increasing the perceived volume and irritability of sounds. This, in turn, shifts the focus of attention to the intrusive sound, which affects concentration or the activity being performed.
Hazell, J. Decreased sound tolerance - Hypersensitivity of hearing. [online] Available in: http://tinnitus.org/hyperacusis-etc/
Johnson, M. Soft Sound Sensitive Syndrome. [online] Availabe in: http://www.tinnitus-audiology.com/softsound.html
Cohen, J. 2011. When a Chomp or a Slurp Is a Trigger for Outrage. [online] Available in: http://www.nytimes.com/2011/09/06/health/06annoy.html?_r=1
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