N1m amplitude growth function for bone-conducted ultrasound.
CONCLUSIONS
N1m growth indicates the differences in central auditory processing between bone-conducted ultrasound and air-conducted audible sound.


OBJECTIVE
Bone conduction enables ultrasound to be heard by the human ear. Despite many studies, the perceptual mechanism of bone-conducted ultrasound has not yet been clarified completely. Therefore, this study investigated the ultrasonic perception of humans, especially as regards the effects of stimulus intensity or loudness.


METHODS
The effect of the stimulus level on N1m amplitude was measured over the psycho-acoustical dynamic range.


RESULTS
The dynamic range for 30 kHz bone-conducted ultrasound (18.2 +/- 3.3 dB) was found to be significantly narrower than that for 1 kHz air-conducted sound (85.9 +/- 11.9 dB). As the stimulus level increased, the N1m amplitude in response to bone-conducted ultrasound grew faster than that to air-conducted sound. Although the growth of the N1m amplitude for air-conducted sound saturated below the uncomfortable loudness level (UCL), that for bone-conducted ultrasound continued to grow above the UCL.
Department of Otolaryngology, Nara Medical University, Kashihara, Japan. t-nishim@naramed-u.ac.jp
Tadashi
T
Nishimura
Seiji
S
Nakagawa
Akinori
A
Yamashita
Takefumi
T
Sakaguchi
Hiroshi
H
Hosoi
D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D001303:Auditory Cortex / Q000502:physiology; D001307:Auditory Perception / Q000502:physiology*; D001844:Bone Conduction / Q000502:physiology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D014465:Ultrasonics