Multiple Scattering Between Adjacent Sound Sources in Head-Related Transfer Function Measurement System

Abstract

To accelerate head-related transfer functions (HRTFs) measurement, two or more independent sound sources are usually employed in the measurement system. However, the multiple scattering between adjacent sound sources may influence the accuracy of measurement. On the other hand, the directivity of sound source could induce measurement error. Therefore, a model consisting of two spherical sound sources with approximate omni-directivity and a rigid-spherical head is proposed to evaluate the errors in HRTF measurement caused by multiple scattering between sources. An example of analysis using multipole re-expansion indicates that the error of ipsilateral HRTFs are within the bound of ± 1.0 dB below a frequency of 20 kHz, provided that the sound source radius does not exceed 0.025 m, the source distance relative to head center is not less than 0.5 m, and the angular interval between two adjacent sources is not less than 20 degrees. Similar conclusions under different conditions can also be analyzed and discussed by using this calculation method. Furthermore, the results are verified by measurements of HRTFs for a rigid sphere and a KEMAR artificial head.

Measurement of Head-Related Transfer Functions: A Review

“…Otherwise, some absorption material around or on the source surface is required [109]. In addition to the special sound sources mentioned above, some researchers prefer to use custom-made loudspeakers (broadband drivers with specially designed enclosures) for near-field HRTF measurements [79,116,117].…”

“…For 6-DoF binaural rendering applications, distance-dependent HRTF datasets are required to synthesize realistic nearby virtual sound sources. Therefore, near-field HRTFs should not only be measured for different source directions but also for various distances (see examples in [79,114,117,120]), leading to a greater workload than the measurement of far-field HRTFs. The main differences between the far-and near-field measurements are the measurement distances and the sound sources used (see Section 2.4).…”