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FEATURED ARTICLE
Psychoacoustics of Tinnitus: Lost in Translation
Christopher Spankovich, Sarah Faucette, Celia Escabi, and Edward Lobarinas
Tinnitus: What Is It?
Tinnitus is the perception of sound without an exter- nal source, often experienced as a constant or frequent ringing, humming, or buzzing. Tinnitus is reported by more than 50 million people in the United States alone (Shargorodsky et al., 2010); conservatively 1 in 10 US adults has tinnitus (Bhatt et al., 2016). It is estimated that 20-25% of patients with tinnitus consider the symptoms to be a significant problem (Seidman and Jacobson, 1996).
Various nomenclature has been applied to describe tinnitus, including terms such as subjective or objective tinnitus and the more recent recommended terms primary and second- ary tinnitus (Tunkel et al., 2014). Primary tinnitus refers to tinnitus that is idiopathic and may or may not be associated with sensorineural hearing loss (SNHL; hearing loss (HL) related to dysfunction of the inner ear and auditory nerve). Secondary tinnitus refers to tinnitus that is associated with a specific underlying cause other than SNHL or an identifi- able organic condition such as pulsatile tinnitus (heartbeat perception in ear). Our discussion here is focused on pri- mary tinnitus, which is the more common variant.
Causes of Tinnitus
The understanding of the physiological source of primary tinnitus has significantly expanded over the past 30 years. Numerous portions of the auditory pathway and nonau- ditory neural pathways have been implicated in tinnitus perception and reaction. Still, the exact mechanisms underlying tinnitus remain elusive.
Contemporary research points to both peripheral and central factors that underlie tinnitus. In other words, peripheral changes to the auditory part of the inner ear and auditory neural integrity, most commonly result- ing from noise exposure, ototoxic drugs, and age-related factors, result in compensatory changes/neural plasticity
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https://doi.org/10.1121/AT.2021.17.1.35
at more central segments of the pathway. These changes include (1) an increase spontaneous neural activity of excitatory neurons/neurotransmitters and a reciprocal decrease in activity of inhibitory neurons/neurotransmit- ters, resulting in central gain; (2) distortions in frequency representation as input to more central regions is restricted due to peripheral damage; and (3) nonauditory pathway/structure recruitment, suggesting a multisensory and distributed brain network implicated in mediating tinnitus perception and reaction. Simply stated, tinnitus is the attempt of the brain to fill in the reduced peripheral input (Spankovich, 2019).
Perception Versus Reaction to Tinnitus
A critical distinction is the perception of tinnitus versus the reaction to tinnitus. The tinnitus percept or phantom sound itself has minimal repercussions for morbidity or mortality. Conversely, the reaction or emotional response to tinnitus can have a substantial effect on a person’s functional status (Jastreboff and Hazell, 1993). Almost everyone with tinnitus, whether bothersome or not, would want the percept eliminated if possible (Tyler, 2012).
Clearly, tinnitus is not perceived as a positive experience. The onset of tinnitus perception does not generally evoke a feeling of improved health or well-being. For example,
if you hear a grinding noise in your car engine one day, your first reaction is not positive in nature. The reaction to tinnitus may further be influenced by events related to its onset, where the tinnitus becomes a reminder of that expe- rience (Fagelson, 2007). For example, a person with an acoustic neuroma (tumor of the auditory-vestibular nerve) and its associated tinnitus may experience an enhanced awareness to tinnitus changes and an exacerbated reac- tion due to concern that it is a sign the tumor is growing larger or more invasive. A soldier who has experienced tinnitus during or following an active engagement may be
Volume 17, issue 1 | Spring 2021 • Acoustics Today 35