Interaural Attenuation
Also written as: IA — Interaural Attenuation
The reduction in sound intensity that occurs as a signal crosses from the test ear through the skull to the non-test ear, relevant to determining when masking must be applied during audiometric testing.
Full Definition
Interaural attenuation (IA) is the loss of sound energy—expressed in decibels—that a stimulus undergoes as it travels by bone conduction from the ear being tested to the contralateral cochlea. The value of IA depends on the type of transducer: supra-aural earphones typically have an IA of approximately 40–50 dB, insert earphones approximately 70–85 dB, and bone conduction oscillators effectively 0 dB. When the test-ear stimulus exceeds the non-test ear's bone conduction threshold by more than the IA value, the contralateral cochlea may respond, creating a 'shadow curve' and requiring masking noise. Editors should ensure that masking rationale sections in audiological reports correctly reference IA values appropriate to the transducer used.
Usage
Usage note: Always specify the transducer type when citing IA values, as the figure varies substantially between supra-aural earphones, insert earphones, and bone conduction oscillators.
In Context
- "Given the interaural attenuation of 40 dB for supra-aural earphones, masking was introduced in the non-test ear when the right-ear air conduction thresholds exceeded 55 dB HL." — Audiological diagnostic report masking rationale
- "The report cited an interaural attenuation of 0 dB for insert earphones, which is incorrect; the typical value is 70–85 dB and must be corrected." — Peer editorial review of audiology methods section