Diplacusis

The term diplacusis has been used in cases which 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.{{Cite journal|last=Burns|first=E. M.|date=1982|title=Pure-tone anomalies. I. Pitch-intensity effects and diplacusis in normal ears|journal=The Journal of the Acoustical Society of America|volume=72|issue=5|pages=1394–1402|doi=10.1121/1.388445|issn=0001-4966|pmid=7175025}}{{Cite journal|last1=Burns|first1=E. M.|last2=Turner|first2=C.|date=1986|title=Pure-tone pitch anomalies. II. Pitch-intensity effects and diplacusis in impaired ears|journal=The Journal of the Acoustical Society of America|volume=79|issue=5|pages=1530–1540|doi=10.1121/1.393679|issn=0001-4966|pmid=3711452|bibcode=1986ASAJ...79.1530B}} 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. On presentation of a single tone alternating between ears (i.e. 1000 Hz left, 1000 Hz right, 1000 Hz left, ...), a given person will consistently mismatch these sinusoids the same amount between trials if doing a pitch-matching task. For example, a 1000 Hz tone in an unaffected ear may be heard as a slightly different pitch in the opposite ear, or have an imperfect tonal quality in the affected ear.

There are two theories on the cause of diplacusis: place theory and temporal theory.{{Cite journal|last=Oxenham|first=Andrew J.|date=2013|title=Revisiting place and temporal theories of pitch|journal=Acoustical Science and Technology|volume=34|issue=6|pages=388–396|doi=10.1250/ast.34.388|issn=1346-3969|pmc=4215732|pmid=25364292}} 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.{{Cite journal|last1=Oxenham|first1=Andrew J.|last2=Micheyl|first2=Christophe|last3=Keebler|first3=Michael V.|last4=Loper|first4=Adam|last5=Santurette|first5=Sébastien|date=2011-05-03|title=Pitch perception beyond the traditional existence region of pitch|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=108|issue=18|pages=7629–7634|doi=10.1073/pnas.1015291108|issn=1091-6490|pmc=3088642|pmid=21502495|doi-access=free}}

Temporal theory posits that the cause is from looking at the phase locking to tell what the pitch is. This theory has a difficult time explaining diplacusis. There are some examples of pitch which do not have an "edge" on the basilar membrane, which this would account for—e.g., white noise, clicks, etc. Both theories are under debate.{{Cite journal|last1=Verschooten|first1=Eric|last2=Shamma|first2=Shihab|last3=Oxenham|first3=Andrew J.|last4=Moore|first4=Brian C. J.|last5=Joris|first5=Philip X.|last6=Heinz|first6=Michael G.|last7=Plack|first7=Christopher J.|date=2019|title=The upper frequency limit for the use of phase locking to code temporal fine structure in humans: A compilation of viewpoints|journal=Hearing Research|volume=377|pages=109–121|doi=10.1016/j.heares.2019.03.011|issn=1878-5891|pmc=6524635|pmid=30927686}}{{Cite journal|last=Oxenham|first=Andrew J.|date=2018-01-04|title=How We Hear: The Perception and Neural Coding of Sound|journal=Annual Review of Psychology|volume=69|issue=1|pages=27–50|doi=10.1146/annurev-psych-122216-011635|issn=0066-4308|pmc=5819010|pmid=29035691}}

Normal human ears can discriminate between two frequencies that differ by as little as 0.2%.{{Cite journal|last1=Micheyl|first1=Christophe|last2=Xiao|first2=Li|last3=Oxenham|first3=Andrew J.|date=2012|title=Characterizing the dependence of pure-tone frequency difference limens on frequency, duration, and level|journal=Hearing Research|volume=292|issue=1–2|pages=1–13|doi=10.1016/j.heares.2012.07.004|issn=0378-5955|pmc=3455123|pmid=22841571}} If one ear has normal thresholds while the other has sensorineural hearing loss (SNHL), diplacusis may be present, as much as 15–20% (for example 200 Hz one ear => 240 Hz in the other).{{Citation needed|date=September 2019}} The pitch may be difficult to match because the SNHL ear hears the sound "fuzzy". Bilateral SNHL gives less diplacusis, but pitch distortions may persist. This may cause problems with music and speech understanding.

Treatment of diplacusis includes a full medical and audiological examination that may explain the nature of the problem. If needed, amplification may relieve the symptoms of diplacusis. Therapy in helping the patient understand the cause of the symptom and tinnitus retraining may provide some relief. In at least some cases, amplification makes no difference and there is no treatment other than waiting for natural resolution. Some individuals may find the provided amplification also increases the audibility of their pitch discrepancy. If onset is linked to an underlying medical cause, i.e. sudden sensorineural hearing loss, appropriate medical treatment is recommended.

Diplacusis is from the Greek words "diplous" (double) and "akousis" (hearing).{{Cite journal|date=1921|title=Surgical Clinics of Chicago|journal=California State Journal of Medicine|volume=19|issue=1|pages=36–37|issn=0093-402X|pmc=1516741}}

• Audiology
• Health problems of musicians
• Hearing
• Hearing loss
• Pitch (psychophysics)
• Auditory system
• Safe listening

• Diplacusis: I. Historical Review{{Cite journal|last1=Albers|first1=G. D.|last2=Wilson|first2=W. H.|date=1968|title=Diplacusis. I. Historical review|journal=Archives of Otolaryngology|volume=87|issue=6|pages=601–603 contd|doi=10.1001/archotol.1968.00760060603009|issn=0003-9977|pmid=4871882}}
• 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.
• [https://Diplacusis.com Diplacusis.com] - discussion with skew graphs

Category:Pitch (music)

Category:Psychoacoustics

Category:Audiology

Category:Hearing loss