Bone Conduction and Transcranial Attenuation
Stenfelt measured bone conduction (BC) pure tone thresholds via the Hughson-Westlake 1 dB protocol in 28 unilaterally deaf adults (average age 50 years) to determine frequency-specific transcranial attenuation levels (i.e., the difference between ipsi and contralateral stimulation in dB). Stenfelt evaluated 1/6th octave frequencies (31 separate frequencies) from 250 to 8000 Hz. The BC stimulator was located at four separate locations including ipsi and contralateral mastoid, as well as ipsi and contralateral bone-anchored-hearing-solution (BAHS) surgical locations (approximately 55 mm posterior to the ear canal). Presentation order was balanced.
Stenfelt reports dramatic inter-subject differences of up to 40 dB for most frequencies. Nonetheless, for mastoid stimulation, the median attenuation is 3 to 5 dB up to 500 Hz and approximately 0 dB from 1000 to 1800 Hz. Median attenuation is roughly 10 dB from 3000 to 5000 Hz, and at 8000 Hz, median attenuation is 4 dB.
In general, when the BC stimulator was placed at the surgical location, the attenuation is 2 to 3 dB less than the mastoid location.
For More Information, References, and Recommendations
Ho EC, Monksfield P, Egan E, Reid A, Proops D. (2009) Bilateral Bone-Anchored Hearing Aid: Impact on Quality of Life Measured with the Glasgow Benefit Inventory. Otology & Neurotology (30)7:891–896.
Popelka GR, Derebery J, Blevins NH, Murray M, Moore BCJ, Sweetow RW, Wu B, Katsis M. (2010) Preliminary Evaluation of a Novel Bone-Conduction Device for Single-Sided Deafness. Otology & Neurotology 31: 492–497.
Stenfelt, S. (2012) Transcranial Attenuation of Bone-Conducted Sound When Stimulation Is at the Mastoid and at the Bone Conduction Hearing Aid Position. Otology & Neurotology 33(2):105–114.
Tjellstrom A. (2010) Bone-Anchored Hearing Aids: From a Test Project to An Established Clinical Routine. ENT & Audiology News 19(1):38–40.
Toll LE, Emanuel DC, Letowski T. (2011) Effect of Static Force on Bone Conduction Hearing Thresholds and Comfort. International Journal of Audiology 50:632–635.