An acoustic shock is an involuntary startle and fright reaction to a sudden, loud, unexpected sound, leading to a typical cluster of involuntary, highly specific symptoms.
Acoustic Shock becomes an acoustic shock disorder or acoustic shock injury if symptoms persist. Acoustic Shock needs to be distinguished from, and is separate and different to, inner ear damage from noise exposure, also known as acoustic trauma, causing a noise induced hearing loss.
The acoustic incident resulting in an acoustic shock is always an unexpected or unpredictable sound, triggering a strong startle and threat response.
Additionally, acoustic incidents leading to acoustic shock are often:
Call centre staff wearing a headset are vulnerable to acoustic shock, and the research has tended to focus on this group.
However, acoustic incidents can occur anywhere.
Acoustic incidents through a telephone line can originate as feedback oscillation, fax tones, signalling tones, or even malicious whistleblowing by dissatisfied call centre customers. Acoustic shock symptoms can develop as a result of cumulative exposure to sustained headset use. In some call centre cases, this can occur without a specific acoustic incident being identified.
Typically, people experiencing an acoustic shock describe it like being stabbed or electrocuted in the ear.
The initial symptoms can include some or all of the following:
Symptoms usually fade within a few hours or days. In some cases, almost always associated with the development of hyperacusis, some of the symptoms can persist for months or indefinitely. Persistent symptoms are often sound-induced and can include:
Acoustic shock symptoms are involuntary, so they cannot be readily controlled, and subtle or subjective, so they cannot be easily objectively measured. The unusual symptom cluster may be misunderstood or not believed. Persistent symptoms are unpleasant, frightening and can be deeply distressing, potentially leading to a range of emotional reactions including trauma, panic attacks, anxiety disorders and depression.
The immediate cause of acoustic shock symptoms is considered to be excessive contractions of the middle ear muscles (stapedius and tensor tympani muscles), triggered by hearing the acoustic incident. While the stapedial reflex is an acoustic reflex triggered by high volume levels, the tensor tympani reflex is a startle and ‘protective’ reflex with a variable threshold.
Persistent acoustic shock disorder symptoms are consistent with a condition called Tonic Tensor Tympani Syndrome (TTTS). With TTTS, the tensor tympani muscle is spontaneously active, rhythmically contracting and relaxing. This appears to initiate a cascade of physiological reactions in and around the ear.
Symptoms consistent with TTTS can include:
Our Audiology practice provides unique expertise in the evaluation and management of acoustic shock patients and in acoustic shock workplace consultancy.
Ms Myriam Westcott has been working with acoustic shock patients on a frequent basis since 2002. She is the most experienced audiologist internationally in the provision of acoustic shock evaluation and therapy. Myriam has extensive experience in the rehabilitation of tinnitus and hyperacusis, dominant symptoms of acoustic shock disorder.
Our evaluation and management program includes:
In the early 1990s, co-inciding with the rapid growth of call centres around the world, increasing numbers of call centre employees were reporting an unusual symptom cluster after hearing a sudden, unexpected, loud noise (acoustic incident) transmitted via their headset.
These physical and psychological symptoms have become known as acoustic shock.
Call centre staff using a telephone headset or handset are vulnerable to acoustic shock because of the increased likelihood of hearing an acoustic incident close to their ear(s). More generally, acoustic shock can occur following exposure to any sound which gives a severe fright or is associated with a highly traumatic experience.