Acoustic shock

What is acoustic shock?

Acoustic shock is an involuntary severe fright/psychological trauma reaction to an unexpected, sudden sound, which is usually loud, that triggers a characteristic cluster of symptoms in and around the ear(s).

Acoustic shock needs to be distinguished from and is different to cochlear (inner ear) damage from noise, potentially causing a noise induced hearing loss.

Acoustic shock symptoms

Typically, people experiencing an acoustic shock describe it as like being stabbed or electrocuted in the ear.

Immediate symptoms of acoustic shock can include:

severe startle reaction with a head/neck jerk
stabbing pain in the ear
dull ache in the ear, can radiate to cheek, neck, arm
tinnitus, hyperacusis
sensation of fullness/blockage in the ear
sensations of burning, numbness, tingling in and around the ear
mild vertigo, nausea
muffled, distorted hearing (usually subjective with no measurable change in hearing)
shock response: shaking, crying, disorientation, headache, fatigue

Acoustic shock symptoms are highly specific and remarkably consistent, mostly subjective and usually temporary. The symptoms can range in severity from mild to severe to extreme. Acoustic shock symptoms can persist and escalate if hyperacusis develops, becoming an acoustic shock disorder.

What triggers an acoustic shock?

The acoustic incident triggering acoustic shock is an unexpected or unpredictable, sudden sound, inducing a strong startle and fright response, and is usually loud.

Additionally, acoustic incidents leading to acoustic shock disorder often:

have a sharp, impulse quality
occur in close proximity to the ear(s)
are unavoidable: occurring in a situation where the person is unable to move away from the sound. Duration of exposure can be a factor.
are outside the person’s control
are threatening

While the acoustic incident triggering acoustic shock may be loud enough to cause both acoustic shock and inner ear damage, most acoustic shock patients do not have signs or symptoms of damage.

Exposure to repeated acoustic incidents increases acoustic shock vulnerability and symptom persistence or escalation.

What causes acoustic shock symptoms?

Acoustic shock was first identified in call centre workers in response to sounds heard via a headset (Patuzzi, Milhinch and Doyle, 2000, Milhinch 2001, Patuzzi, 2002). Consequently, the (limited) research carried out on acoustic shock has tended to view this as a workplace phenomenon, but a loud sudden unexpected sound in close proximity triggering acoustic shock can (and does) occur anywhere. After call centre workers, in my experience musicians are the next most common group affected.

The immediate symptoms of acoustic shock are considered to be the direct consequence of strong reflex contractions of the stapedial and tensor tympani muscles of the middle ear, triggered by a heightened startle response to the acoustic incident (Patuzzi, Milhinch and Doyle, 2000, Patuzzi, 2002).

Any ongoing, persistent symptoms of acoustic shock are consistent with TTS (Milhinch 2001, Patuzzi 2002, Westcott 2006, Londero et al 2017, Norena et al 2018).

After working intensively with acoustic shock patients from 2002, I realised that acoustic shock symptoms persist, becoming an acoustic shock disorder, if hyperacusis develops from the acoustic shock (Westcott 2010).

For some people, there are no immediate symptoms, but an involuntary, delayed threat response to the acoustic incident triggers hyperacusis. In some call centre cases, acoustic shock symptoms can develop as a result of cumulative sound exposure from sustained headset use leading to hyperacusis, without a specific acoustic incident being identified.

Diagnosis and treatment of acoustic shock

Workplace support

A call centre worker experiencing acoustic shock disorder is vulnerable to a significant exacerbation of their symptoms should they be exposed to any further unexpected, sudden onset, loud sounds via a headset worn on either the affected ear or their other ear.

These patients should not return to headset or telephone duties until their symptoms have resolved. A gently graded return to work, at the patient’s pace, can then be carried out with handset use initially on the opposite ear.

A carefully considered evaluation and diagnosis of acoustic shock can be made by an experienced audiologist on the basis of a thorough case history noting acoustic incident exposure; the onset of symptoms consistent with acoustic shock following acoustic incident exposure; the pattern of symptom persistence and escalation over time; the development of hyperacusis; and any symptom exacerbation following exposure to intolerable (or difficult to tolerate) sounds.

A hearing assessment should be kept brief and done with care, with no loudness discomfort or acoustic reflex testing carried out. Tympanometry and an ENT specialist examination can be highly reassuring to exclude middle ear involvement or alternative aural pathologies.

A rapid diagnosis, with a personalised explanation and TTS symptom treatment, can help limit hyperacusis development or escalation.

Treatment of TTS symptoms, hyperacusis desentisation therapy and tinnitus habituation therapy is indicated, as needed. Psychological support is often required to cope with the physical symptoms, trauma, distress and disruption of acoustic shock disorder.