diplacusis

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/06/12 01:40:31」(JST)

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Diplacusis, also known as diplacusis binauralis or inter aural pitch difference (IPD) is a type of tinnitus that is the perception of a single auditory stimulus as two separate sounds which may differ in pitch or in time. It is typically experienced as a secondary symptom of sensorineural hearing loss, although not all patients with sensory neural hearing loss may experience diplacausis or tinnitus. Onset is usually spontaneous and can occur at the time of an acoustic trauma or in the midst of an ear infection. Sufferers may experience the effect permanently, or it may resolve on its own. Treatment includes a full medical examination as well as an audiological examination that may explain the nature of the problem. If needed, amplification may relieve the symptoms of diplacausis. Therapy in helping the patient understand the cause of the symptom and tinnitus retraining may provide some relief.

Diplacusis of Pure Tones

For people with unilateral cochlear hearing losses or asymmetrical hearing losses, the same tone presented alternately to the two ears may be perceived as having different pitches in the two ears. This is the phenomenon of diplacusis. The magnitude of the shift can be measured by getting the subject to adjust the frequency of a tone in one ear until its pitch matches that of the tone in the other ear.

If a 1000 Hz pure tone is presented in both of a listener's ears, then they perceive one pitch^{[citation needed]}. However, alternate the presentation between ears (i.e. 1000 Hz left, 1000 Hz right, 1000 Hz left, ...), and a given person will consistently mismatch these sinusoids the same amount between trials if doing a pitch-matching task.

Biological Explanation via Theories of Pitch of Pure Tones

There are two theories on the cause of diplacusis: place theory and temporal theory.

Place Theory posits that the cause is looking for the edge of the wave for the pitch and could explain diplacusis as a small differences between the two cochleas.

Temporal Theory posits that the cause is from looking at the phase locking to tell what the pitch is. This theory has a hard time explaining diplacusis. There are some examples of pitch which don’t have an "edge" on the basilar membrane, which this would account for—i.e. white noise, clicks, etc.

Effects of Sensorineural Hearing Loss (SNHL)

If one ear has normal thresholds and one has SNHL (a unilateral loss), there is a lot of diplacusis. As much as 15 – 20% (for example 200 Hz one ear => 240 Hz in the other). Hard to match because the SNHL ear hears it “fuzzily”.

Bilateral SNHL gives less diplacusis, but pitch distortions may persist. This may cause problems with music and speech understanding.

References

Turner, Christopher. "Perception of Pitch." Wendell Johnson Speech and Hearing Center, Iowa City. Dec. 2008.
Plack et al. (Ed).Pitch : Neural coding and perception. Springer. 2005

English Journal

Octave illusion elicited by overlapping narrowband noises.

Jonas Brännström K, Nilsson P.SourceDepartment of Clinical Science, Section of Logopedics, Phoniatrics and Audiology, Lund University, SE-221 85 Lund, Sweden.
The Journal of the Acoustical Society of America.J Acoust Soc Am.2011 May;129(5):3213-20. doi: 10.1121/1.3571425.
The octave or Deutsch illusion occurs when two tones, separated by about one octave, are presented simultaneously but alternating between ears, such that when the low tone is presented to the left ear the high tone is presented to the right ear and vice versa. Most subjects hear a single tone that a
PMID 21568423

Investigating possible mechanisms behind the effect of threshold fine structure on amplitude modulation perception.

Heise SJ, Mauermann M, Verhey JL.SourceInstitut fur Physik, Universitat Oldenburg, D-26111 Oldenburg, Germany. stephan.heise@uni-oldenburg.de
The Journal of the Acoustical Society of America.J Acoust Soc Am.2009 Nov;126(5):2490-500. doi: 10.1121/1.3224731.
Detection thresholds for sinusoidal amplitude modulation at low levels are higher (worse) when the carrier of the signal falls in a region of high pure-tone sensitivity (a minimum of the fine structure of the threshold in quiet) than when it falls at a fine-structure maximum. This study explores pos
PMID 19894829

Japanese Journal

内リンパ水腫蝸牛に対する強大音負荷後のAP閾値上昇の検討

西川典秀,伊東善哉,武山実,阿瀬雄治,和田哲郎,木村伸一,草刈潤,中田穂出美
Equilibrium Research 51(Suppl-8), 45-51, 1992
… This change in the hydrodynamics of the cochlea may explain the mechanism of the development of diplacusis in Ménière's disease. …
NAID 130000855106

［第22回前庭研究会］最近におけるニエル病の諸問題:内リンパ水腫の立場から

内藤儁
耳鼻と臨床 14(Supplement1), 37-39, 1968
… pressure. 3) Touching of dilated saccule on the footplate of stapes. 4) Pressed or agglutinated organ of Corti. Of course another important factor causing deafness is changes of blood circulation in the inner ear. Tullio's phenomenon and diplacusis biauralis dysharmonica were discussed from the stand point of endolymphatic hydrops. Portmann's operation and Yamakawa-Naito's operation on the endolymphatic sac were mentioned. Experimental studies on the endolymphatic hydrops performed by the author and …
NAID 130004401638