Re: sounds too loud

[Martin Braun <nombraun@xxxxxxxxxxxxxxx>]

Jont Allen wrote:

> Does anybody know of a condition where a person complains that sounds are
too loud.
> Does this condition have a name?
> Is it a physiological condition, with a known cause?

There is a large clinical survey on this issue:

Hallpike and Hood (1959) measured recruitment and over-recruitment in 200
patients with unilateral Menière's disease. The applied audiological
technique was the "alternate binaural loudness balance" (Fouler test). All
200 patients showed recruitment in the affected ear, no matter if this ear
had any significant hearing loss or not. Most importantly, two-thirds of
these ears also showed over-recruitment. Over-recruitment means (as
correctly reported to this list on Jan 19 by Brent Edwards) that above a
certain sound level, say 80 dB, the affected ear hears louder than the
healthy ear.

Hallpike, C.S. and Hood, J.D. (1959) Observations upon the neurological
mechanism of the loudness recruitment phenomenon. Acta Otolaryngol.
(Stockh.) 50, 472-486.

[The discussion of possible causes is no longer useful today, but the
empirical data are classical.]

Because Menière's disease is a cochlear-vestibular disease, hyperacusis in
these patients is assumed to have cochlear origins. Hair cell damages can
not be a necessary element, because even affected ears without hearing loss
often have hyperacusis. The only plausible hypothesis is a mechanical one.
Expansion of the inner ear endolymph (called "endolymphatic hydrops"), which
is present in all cases of Menière's disease, displaces various cochlear
components and reduces the normal cochlea's capacity of absorbing high-level
acoustic energy. The loss of inner-ear dampening leads to an increased hair
cell excitation, and thus increased  loudness sensation, at medium and high
sound levels. A large amount a experimental and clinical evidence on the
relation of hyperacusis and inner ear mechanics was reviewed by Braun
(1996).

Braun, M. (1996) Impediment of basilar membrane motion reduces overload
protection but not threshold sensitivity: evidence from clinical and
experimental hydrops. Hear Res 97, 1-10.

Martin


Martin Braun
Neuroscience of Music
Gansbyn 14
S-671 95 Klässbol
Sweden
nombraun@post.netlink.se