Development of Micro-Dodecahedral Loudspeaker for Measuring Head-Related Transfer Functions in The Proximal region

This paper describes new equipment for measuring head-related transfer functions (HRTFs) near a listener´s head. 3D sounds in headphones are generated by the convolution of sound signals and an HRTF, which is defined as the acoustical transfer function between a point sound source and the entrance to the ear canal. A loudspeaker is usually used for HRTF measurements, and a distance of more than 1 m separates the loudspeaker and the subject. The region within 1 m of the head is called the ´proximal region,´ where a small loudspeaker is needed for accurately measuring HRTF, that is, a conventional loudspeaker cannot be used. In our study, a micro-dodecahedral loudspeaker with twelve piezoelectric ceramic devices is used for HRTF measurements at a diameter is 38 mm. Our experiments examined the characteristics of this loudspeaker. From the results, our developed loudspeaker provides similar performance to a point source, and it is very effective for measuring the HRTFs in the proximal region