Robots with sound localization capability have been developed mostly relying on machine vision or an array of more than two microphones. Humans can localize a sound source hidden to the eye and distinguish whether a sound is coming from front or rear, above or below with only two ears. This is mainly due to the complex shape of the pinna. In particular, reflections off the posterior wall of the concha produce spectral notches at different frequencies in the head-related transfer function (HRTF) as the sound source shifts in position. From the non-individualized HRTFs measured with a B&K HATS (head and torso simulator), we were able to confirm the relationship between the spectral notches and the geometry of the concha. Based on the observation of the HATS' pinna and resulting HRTFs, a novel design of artificial ear that can be mounted on a robot head is proposed in order to explore the possibility of developing sound localization sensors using only two microphones. Experimental results using a designed artificial ear show that the spectral notches are distinctively changed with respect to the elevation in the frontal region, whereas they disappear in the rear. In view of that result, it is expected to pinpoint a sound direction in 3-D space using only two microphones and the designed artificial ear can be a suitable mechanical sensor for sound source localization.
[1]
Nobuhiko Kitawaki,et al.
Common-acoustical-pole and zero modeling of head-related transfer functions
,
1999,
IEEE Trans. Speech Audio Process..
[2]
E. Shaw,et al.
Sound pressure generated in an external-ear replica and real human ears by a nearby point source.
,
1968,
The Journal of the Acoustical Society of America.
[3]
J. Hebrank,et al.
Spectral cues used in the localization of sound sources on the median plane.
,
1974,
The Journal of the Acoustical Society of America.
[4]
E. Langendijk,et al.
Contribution of spectral cues to human sound localization.
,
1999,
The Journal of the Acoustical Society of America.
[5]
Kazuhiro Iida,et al.
Upper hemisphere sound localization using head-related transfer functions in the median plane and interaural differences
,
2003
.
[6]
R Meddis,et al.
A physical model of sound diffraction and reflections in the human concha.
,
1996,
The Journal of the Acoustical Society of America.
[7]
E. Shaw,et al.
External-ear acoustic models with simple geometry.
,
1968,
The Journal of the Acoustical Society of America.
[8]
M. Morimoto,et al.
Localization cues of sound sources in the upper hemisphere.
,
1984
.
[9]
Youngjin Park,et al.
Modeling of non-individualized head-related transfer functions for nearby sources
,
2006
.