Towards mass-customizing non-individualized head-related transfer functions: a preliminary study.

Individualized head-related transfer function (HRTF) devices can generate virtual surround sound but are expensive to obtain. This paper presents the preliminary findings of a study, funded by the Hong Kong Research Grants Council, to establish design methodologies for customizing non-individualized HRTFs at mass-production cost and efficiency. The long-term objective of the study is to replace the expensive individualized HRTFs with inexpensive customizable non-individualized HRTFs. Ear and head dimensions of over 400 HK Chinese participants were measured and four groups of listeners with significantly different ear dimensions were identified. Two listeners from each group were selected to take part in a sound localization experiment. Results indicate that listeners with different ear dimensions are associated with significantly different sound localization error rates. Individualized HRTFs for four participants (one from each group) were measured at Ruhr-Universitat Bochum, Germany, using innovative methods. Analyzes of these four HRTF sets indicate observable differences in spectral characteristics that may explain the significant differences in their sound localization performance. The current preliminary finding suggests a possible linkage among normalized ear dimensions (namely, fossa height / pinna height; helix height / pinna height; and cavum concha area / pinna area), sound localization performance and spectral characteristics of HRTFs. Currently, most digital audio products are manufactured in China but the profit margins for such products are decreasing annually. If industrialists in Hong Kong can acquire the ability to produce customizable virtual surround sound systems at low cost, new innovative products with much greater profit margins can be designed and produced.