Is cartilage conduction classified into air or bone conduction?
OBJECTIVES/HYPOTHESIS
The aim of this study was to establish the sound transmission characteristics of cartilage conduction proposed by Hosoi (2004), which is available by a vibration signal delivered to the aural cartilage from a transducer.


STUDY DESIGN
Experimental study.


METHOD
Eight volunteers with normal hearing participated. Thresholds at frequencies of 0.5, 1, 2, and 4 kHz for air conduction, bone, and cartilage conductions were measured with and without an earplug. The sound pressure levels on the eardrum at the threshold estimated with a Head and Torso Simulator were compared between air and cartilage conductions. The force levels calibrated with an artificial mastoid at the threshold were compared between bone and cartilage conductions.


RESULTS
The difference in the estimated sound pressure levels on the eardrum at the thresholds between air and cartilage conductions were within 10 dB. In contrast, the force levels at the thresholds for cartilage conduction were remarkably lower than those for bone conduction. These findings suggested that sounds were probably transmitted via the eardrum for cartilage conduction. The threshold shifts by an earplug showed no significant difference between bone and cartilage conductions at 0.5 kHz. At 1 and 2 kHz, the threshold-shifts increased significantly in the order of bone, cartilage, and air conductions. These results suggested that airborne sound induced by the vibration of the cartilaginous portion of the ear canal played a significant role in sound transmission for cartilage conduction.


CONCLUSIONS
Cartilage conduction has different characteristics from conventional air and bone conductions.
['Nishimura|Tadashi|T|', 'Hosoi|Hiroshi|H|', 'Saito|Osamu|O|', 'Miyamae|Ryosuke|R|', 'Shimokura|Ryota|R|', 'Matsui|Toshie|T|', 'Yamanaka|Toshiaki|T|', 'Levitt|Harry|H|']
D000161:Acoustic Stimulation D000328:Adult D000388:Air D001309:Auditory Threshold D001844:Bone Conduction D004424:Ear Canal D004425:Ear Cartilage D005260:Female D006801:Humans D008297:Male D014732:Vibration
aural cartilage airborne sound Occlusion effect aural atresia bone anchored hearing aid