Acoustic trauma and Acoustic Shock are separate and distinct conditions resulting from exposure to loud sounds.
Acoustic trauma (AT) is a physical injury to the hearing mechanism of the inner ear. AT results from exposure to sounds loud enough to cause physical damage to delicate structures within the cochlea. AT may follow a single exposure to an extremely high-volume loud, or repeated exposures to sounds of lesser volume, but still strong enough to inflict physical damage.
Acoustic Shock (AS) represents a group of very real physiologic symptoms resulting from a specific sound-exposure experience. AS typically occurs after exposure to a sudden and unexpected loud sound perceived as highly threatening (an acoustic incident.) AS becomes Acoustic Shock Disorder (ASD) if symptoms persist beyond a few hours to a few days.
Acoustic Shock Disorder (ASD)
The physical symptoms of ASD differ from those following a traditional noise injury (AT) and may include the following:
• a shock/trauma reaction. Severe ASD can lead to Post Traumatic Stress Disorder (PTSD)
• sensations of pain/blockage/pressure/tympanic fluttering in the ear
• subjective muffled or distorted hearing. ASD generally does not result in a hearing loss, although if present it tends not to follow the typical high frequency pattern of a noise induced hearing injury (AT) but affects low and mid frequency sensorineural hearing.
• other sensations including pain/burning/numbness around the ear/jaw/neck
• tinnitus, hyperacusis, and phonophobia (abnormal fear of sound)
• mild vertigo and nausea
Victims of AS often describe the initial sensation as like being stabbed or electrocuted in the ear. The initial response often includes a severe startle reaction with a head and neck jerk.
The dominant factors of an acoustic incident leading to ASD appear related to: 1) the sudden onset, 2) unexpectedness, and 3) impact quality of loudish sounds, 4) outside the person’s control, 5) heard near to the ear(s), rather than to high sound-volume levels alone.
Tonic Tensor Tympani Syndrome (TTTS)
The physiological symptoms of AS are considered to be a direct consequence of excessive, involuntary, middle-ear muscle contractions caused by a strong startle response to an acoustic incident. Middle ear muscle contractions, particularly of the tensor tympani muscle, have been demonstrated to occur as part of the startle reflex. Originally described by Dr. I. Klockhoff, this condition of abnormally increased muscle tone and contractions is termed Tonic Tensor Tympani Syndrome, or TTTS.
With TTTS, increased involuntary activity develops in the tensor tympani muscle as part of the startle and protective response to some sounds. This lowered reflex threshold for tensor tympani muscle contraction appears to be activated by the anticipation of sounds perceived as threatening, and the subconscious perception of these sounds as potentially damaging (i.e. a subconscious fear response.) TTTS activates a series of physiological reactions in and around the ear, which can include: alterations in tympanic membrane tension; an abnormal stimulation of the trigeminal nerve innervating the tensor tympani muscle; alterations in ventilation of the middle ear cavity; muscular tightness around the ear potentially extending to the cervical/shoulder girdle and upper limb muscles, muscular trigger points consistent with CNS pain pathway sensitization; and to a lesser extent abnormal stimulation of the nerves innervating the tympanic membrane and ossicular chain (tiny bones of hearing.)
The more extreme the resultant middle ear reflex contractions, the more severe the TTTS symptoms become, worsening the associated trauma reaction.
Once TTTS has become established, the range of sounds that elicit this involuntary response may increase to include everyday sounds, leading to the development and escalation of hyperacusis and phonophobia. A subsequent acoustic incident can lead to a highly enhanced startle response, so that repeated acoustic incidents can significantly enhance ASD vulnerability.
One recent study* reported that one or more symptoms consistent with TTTS were reported in 81.1% of patients with hyperacusis and in 40.6% of those with tinnitus only.
Symptoms consistent with TTTS are subjective and can cause high levels of anxiety. This can lead to tinnitus escalation, the development and escalation of hyperacusis, and limit the effectiveness of tinnitus or hyperacusis therapy.
There is strong evidence that middle ear muscle function is influenced by the serotoninergic system, consistent with a link between the emotional state and middle ear muscle contraction.
The central mediation of the reflex threshold for tensor tympani muscle activity is further supported in the cited study* by:
• The association demonstrated between hyperacusis and the high prevalence of symptoms consistent with TTTS
• The prevalence of symptom development/exacerbation following intolerable sound exposure, consistent with a stress/anxiety/threat response
Fear of the pain experience is one of the factors playing a significant role in explaining avoidance of sounds by people with hyperacusis. Hyperacusis clients often suffer tremendous fear of any situation where they risk sound‑induced pain.
The Promising Role of Energy Psychology
Several of my earlier posts have explained the process of habituation in relieving the suffering for victims of tinnitus or hyperacusis.
Habituation means that the brain develops a habit of automatically ignoring any stimulus it has determined to be non-threatening. This process is mediated through the fear center of our brains (limbic system.) Until fear is removed from the noise of tinnitus, habituation becomes impossible. Once habituation takes place, the brain automatically ignores the noise of tinnitus as though the noise no longer exists – unless the victim elects to focus upon it.
Experience over many thousands of applications has shown that Emotional Freedom Techniques (EFT™,) and Anxiety Relief Techniques® (ART) can quickly and permanently remove fears associated with A) the noise of tinnitus or B) hyperacusis.
It seems highly probable that by unhooking the fear response from TTTS, excessive, involuntary contractions gradually subside in the tensor tympani muscles of ASD victims. This can readily explain why these methods are so effective for those who suffer from this condition.
Suffering from the noise of tinnitus and/or the fear associated with hyperacusis are very real physical conditions. Clinical studies such as cited in this post have given us a much better understanding of the exact mechanisms for this suffering.
The link is much clearer now between A) the associated anxiety and fear responses of tinnitus or hyperacusis with B) hyper-contractility of the tensor tympani muscle in the middle ear.
My experience is that nothing has proven more effective than EFT and ART for removing fear responses from any source. TTTS and ASD should respond equally as well.
* Westcott M, Sanchez TG, Diges I, Saba C, Dineen R, McNeill C, et al. Tonic tensor tympani syndrome in tinnitus and hyperacusis patients: A multi-clinic prevalence study. Noise Health 2013;15:117-28.