Hallucinations in silence
I have been asked about recent claims that very quiet anechoic chambers can cause hallucinations. We have an ultra-silent anechoic chamber around the corner from my office as part of the Acoustic Labs at University of Salford.
In a very quiet anechoic chamber no sound from the outside world enters you ear canals. That does not mean, however, that you hear silence. You might hear the blood gently pumping through your head, or a high-pitched hiss caused by spontaneous firings of the auditory nerve. Normally, these internal sounds are masked by external noises and so are inaudible. If you have tinnitus (ringing in the ears), then it becomes very obvious in an anechoic chamber. But none of these effects are hallucinations. In the 20+ years I’ve been at Salford I’ve never heard of anyone claiming to have suffered hallucinations.
Stories claiming that anechoic chambers cause hallucinations in 15 minutes were prompted by a study by Mason and Brady . They placed people in a completely dark and silent space for 15 minutes. Some test subjects were very susceptible to hallucinations and they saw “objects that were not there, five had hallucinations of faces, four reported a heightened sense of smell, and two felt there was an evil presence in the chamber with them.”  Mason and Brady also tested less susceptible individuals who had fewer hallucinations. However, Vaughan Bell has questioned whether the experimental method rather than the silence caused hallucinations through heightened anxiety.
I’ve never tried sitting in complete darkness in our anechoic chamber, but I have been in a flotation tank. These are silent, and pitch-black and look like a large meat safe. You float in the nude in brine at body temperature. I did this as part of research for The Sound Book (coming out in 2014). During the two hours floating in the tank, the weirdest sensation I got was the feeling that my hands and feet were detached from me because I couldn’t feel my arms or legs. That is the closest I got to a hallucination.
Hallucinations or not, visiting the anechoic chamber is strange and unnerving experience. We are hoping to open the chamber for public tours for one day during the Manchester Science festival 2013.
Have you had hallucinations in an anechoic? If yes, tell me of your experience below
 Journal of Nervous and Mental Disease, The psychotomimetic effects of short-term sensory deprivation, Mason OJ, Brady F.; 197(10):783-5
My experience from working in anechoic chambers has not been hallucinations as such, but after a while my thoughts go in to overdrive, I start thinking of odd things, sometimes felt anxiety and paranoia and had to walk out to get some air. I did fall asleep in one once, I had that ‘detached’ feeling and have never had such vivid dreams. I have also felt a little sickly, hearing your heart beat and blood gushing makes me feel a little uneasy.
Had people new to anechoic chambers faint or have to rush out after 5 minutes because they were going to be sick (and some were sick!).
Wouldn’t want them sick in our chamber, imaging trying to clean the mess out of the floor absorbent. It was bad enough with the duck poo (http://www.acoustics.salford.ac.uk/acoustics_info/duck/)
I’ve had auditory hallucinations a few times when it has been extremely quiet (the countryside at night and in an anechoic chamber). Usually it’s several lines of buzziness at different pitches which move around, but is distinct from circulation or nervous system noises. I think being used to the city my brain is searching for the ‘missing’ sound. A very quiet space will often also trigger ‘earworms’ too, fragments of music which repeat. A few times I’ve also had the experience of hearing my dog (who wasn’t actually there).
I work in accoustic complains evaluations (state office) with very good equipment (sounlevel meter type1 with data and sound recording, soft , calibrator etc so as to asure the quality work and avoid legal liability) for about 34 years. I hope someday i can have the experience of staying a real anechoic chamber. I fantasy that could be good for one although the bad also. Thanks for the article.
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If silence causes hallucinations, then all deaf people would suffer from hallucinations. I’m profoundly deaf and can go days without hearing anything and I don’t suffer from hallucinations. So I’m curious as to why silence triggers hallucinations for hearing people and not for deaf people.
Because they hear their scalp moving, eyes rolling, blood travelling, heart beating, they won’t be able to walk or stand up. It’d be very unnerving, I think I’d start crying, not because it’s frightening but because I’d be hearing the things that are keeping me alive, I’d be pretty grateful. Deaf people don’t hear any of that.
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because your ears control your balance and they are “much more” accurate in someone that actually ears. i think you are no just def of your ears. you simple don’t get that sound is waves traveling in space. if you have no reflexions to guide you, you will get dizzy. think mcfly.. think!
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