There have been several studies on the development of hyperacusis, tinnitus, and tonic tensor tympani syndrome (TTTS) in call center workers. The development of such symptoms after sudden loud sounds is referred to as Acoustic Shock Disorder (ASD). Studies in ASD do a particularly good job of showing that symptoms of TTTS (e.g. aural fullness and ear pain) can develop after an acoustic injury and it does not always involve the development of hyperacusis.
Studies of the prevalence of acoustic shock in call center employees vary significantly. While some call centers report no incidents of acoustic shock, a study of Indian call center employees found 28% had experienced acoustic shock symptoms at least once during their career (Subbarayalu 2013). Call center employees work in an environment that is particularly demanding on the auditory system. They predominantly use headsets, maintain primary focus on their auditory senses without the help of visual cues, and experience unexpected interruptions by sudden, loud sounds. Below are examples of unexpected sounds these workers are regularly exposed to:
- Incorrectly dialed fax machines.
- Faults on the telephone line that cause loud shrieks
- Maliciously generated noises – screaming or blowing a whistle down the line.
- Mobile phone interference.
- Callers dropping their handset on to a desktop.
A 2001 study of 104 cases of acoustic shock in Australia found the following symptom prevalence
- Ear Pain (81%)
- Tinnitus (50%)
- Loss of balance (48%)
- Hyperacusis (32%)
- Vertigo and Nausea (15%)
- Headaches (9%)
A description of a scenario of acoustic shock is provided by Patuzzi,
“A ‘typical’ incident may involve the occurrence of one high-intensity, high frequency monaural squawk, without warning (around 2-3kHz, level below 120 dB SPL). The consultant removes the headset in seconds. In extreme cases they ‘fall’ to the ground immediately, and quickly experience a varied combination of tinnitus, vertigo, feeling of fullness in the ear, hearing loss (in very few cases), numbness, tingling, tenderness or soreness around the ear and neck, ear pain and often burning sensations.” -Patuzzi 2002
Many acoustic shock disorder symptoms are thought to be related to TTTS. More information can be found in Potential Mechanisms: Middle Ear-TTTS.
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