Bone conduction equal-loudness contours: placement, frequency, and intensity
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Type of Workapplication/pdf
xii, 102 pages
DepartmentTowson University. Department of Audiology, Speech-Language Pathology and Deaf Studies
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There are no restrictions on access to this document. An internet release form signed by the author to display this document online is on file with Towson University Special Collections and Archives.
Bone conduction communication is supplemental to air conduction in normal hearing individuals; however, bone conduction devices have advantages compared to air conduction devices in certain circumstances. Air conduction devices such as headphones require the open ear canal to be covered, which causes attenuation of surrounding environmental sounds. With a bone conduction device, the ear canal can be left open allowing the signal to be transmitted without affecting awareness of surrounding noise, which is required for military communication and optimal for recreational communication purposes. However, additional research is needed to optimize the use of bone conduction communication devices. This study was conducted to develop bone conduction equal-loudness contours at mastoid and condyle placements. A portion of these results were compared to existing and well-established air conduction contours, while bone conduction contours were unique to this study. Thirty participants (15 males and 15 females) were trained to compare the loudness of two narrow band noise stimuli and three types of comparisons were made: soundfield to soundfield, soundfield to bone conduction, and bone conduction to bone conduction. This study had 3 goals: (1) to establish equal loudness contours for sound field stimuli and compare these to data previously published, (2) to compare sound field to bone conduction loudness levels at the same frequencies to compare loudness judgments across modality, and (3) to establish bone conduction loudness contours with unilateral and bilateral application in mastoid and condyle locations. Data analysis was conducted using repeated measures ANOVA, dependent t-tests and paired sample t-tests. Results indicated that condition, placement, and intensity were not statistically significant between the bone conduction equal loudness contours at 20 and 40 dB HL. Frequency was significant in each bone conduction equal loudness contour at 20 and 40 dB HL. Paired sample t-tests were conducted to examine differences with the current study's soundfield-to-bone data. Results showed that statistically significant differences were present at 250 and 1000 Hz. Dependent t-tests were conducted to compare the published ISO 2003 values to the current study's soundfield values at 40 dB HL. Results indicated that there were no statistically significant differences between the curves.