Hearing mechanisms:
The auditory system is divided into 3 parts. The outer ear
consists of the external ear (the pinna) and the ear canal.
The middle ear is a cavity between the eardrum and the inner
ear. It is air-filled and is connected to the back of the
throat by the eustachian tube, which opens during swallowing
and yawning and allows air to enter the middle ear, thus enabling
the pressure in the middle ear to be maintained. The inner
ear consists of the cochlea and
the vestibular labyrinth. The latter is part of the systems
controlling the balance mechanisms of the body.
Sound waves are transmitted by the eardrum through the middle
ear as vibrations, which in turn are amplified by a series
of small bones, attached to the eardrum at one end and to
the oval window of the inner ear at the other. The sound waves
are converted to electrical impulses by specialized cells
in the cochlea, the outer hair cell (OHC). The impulses are
then transmitted to the auditory cortex of the brain in the
temporal lobe by the auditory nerve (cranial nerve 8).
The OHC generates sounds (emissions) because the cells have
spontaneous motility, that causes backward energy propagation
from the cochlea to the middle ear, and then to the ear canal,
where they can be recorded using a special microphone. These
emissions are called otoacoustic emissions (OAE). A special
type is distortion product otoacoustic
emissions (DPOAE), which are evoked by stimulation with
two pure tones of different frequencies.
Aran and colleagues (2004) studied the effect on the ear mechanisms
of exposing guinea pigs to RFR at 900 MHz frequency (SAR 1,
2 or 4 W/kg). They found no evidence of any damage to the
inner ear or the auditory pathways. Galloni (2005) found no
effect of 900 MHz RFR on the cochlear
cells of rats. Galloni's group also failed to find evidence
that 900 or 1800 MHz RFR affects the inner auditory system
of rats. Parazzini
(2007) reported no effect of RFR exposure (900 MHz frequency
at 4 W/kg, 2h/d, 5 days a week, for 4 weeks) ± gentamicin
on the auditory system of rats.
Authors
Aran JM, Carrere N, Chalan Y, Dulou PE, et al. (2004):
Title
Effects of exposure of the ear to GSM microwaves: in vivo and
in vitro experimental studies.
Journal
Int J Audiol 43:545-54.
Go to summary>
Authors
Budak GG, Muluk NB, Budak B, Oztürk GG, Apan A, Seyhan N.
Title
Effects of intrauterine exposure to GSM-like radiofrequency on distortion product otoacoustic emissions in infant male rabbits.
Journal
Int J Pediatr Otorhinolaryngol Dec 22, 2008 Ahead of print.
Authors
Budak GG, Muluk NB, Ozturk GG; Budak B; Apan A, Seyhan N, Sanli C.
Title
Effects of GSM-like radiofrequency on distortion product otoacoustic emissions in pregnant adult rabbits.
Journal
Clin Invest Med. (2009). 32(2):E112-6.
Authors
Galloni P, Lovisolo GA, Mancini S, Parazzini M, et al. (2005):
Title
Effects of 900 MHz electromagnetic fields exposure on cochlear
cells functionality in rats: Evaluation of distortion product
otoacoustic emissions.
Journal
Bioelectromagnetics 26:536-547.
Go to summary>
Authors
Galloni P, Parazzini M, Piscitelli M, Pinto R, et al. (2005):
Title
Electromagnetic fields from mobile phones do not affect the
inner auditory system of Sprague-Dawley rats.
Journal
Radiat Res 164:798-804.
Go to summary>
Authors
Galloni P, Lopresto V, Parazzini M, Pinto R, Piscitelli M, Ravazzani P, Marino C.
Title
No effects of UMTS exposure on the function of rat outer hair cells.
Journal
Bioelectromagnetics Feb 25, 2009 Ahead of print.
Authors
Kwon MS, Kujala T, Huotilainen M, Shestakova A, Näätänen R, Hämäläinen H.
Title
Preattentive auditory information processing under exposure to the 902 MHz GSM mobile phone electromagnetic field: A mismatch negativity (MMN) study.
Journal
Bioelectromagnetics Jan 12, 2009 Ahead of print.
Authors
Parazzini M, Galloni P, Piscitelli M, Pinto R et al. (2007):
Title
Possible combined effects of 900 MHz continuous-wave electromagnetic fields and
gentamicin on the auditory system of rats.
Journal
Radiation Research 167:600-605.
Go to summary>
