Modeling, customization, and interpolation of head-related impulse responses based on principal components analysis

Abstract

Virtual Auditory Display (VAD), which is defined as systems or technologies generating spatialized sounds and conveying them to a listener, has been paid much attention in many application fields. The Head-Related Transfer Functions (HRTFs), which describe the physical transform of sound waves due to physical structures of a listener, such as head, pinna, shoulder, and torso, play an important role for rendering of high-fidelity VAD. Recently, three issues, i.e. modeling, customization, and interpolation of HRTFs, are coming into the spotlight for high-fidelity VAD and its real-time implementation. This thesis deals with the three aforementioned issues based on general basis functions. The general basis functions are obtained from Principal Components Analysis (PCA) of HRTFs or Head-Related Impulse Response (HRIR) which is the Fourier Transform pair of the HRTF. The main advantage of using the general basis functions is that the dimension of dataset can be effectively reduced without loss of meaningful information. Four kinds of PCA models based on HRIRs, complex-valued HRTFs, augmented HRTFs, and log-magnitudes of HRTFs are investigated and their modeling performances are compared. In terms of the number of Principal Components (PCs) needed to model the HRTFs or HRIRs with the same accuracy, all the PCA models show almost the same modeling performances. The systematic elevation dependencies in the weights of PCs (PCWs) are observed. The physical meaning of PC and the elevation dependencies of PCWs are explained in detail. In addition, the contribution of each PC to the vertical perception or the front-back discrimination is clarified. The PCs obtained in this thesis includes both the inter-elevation variation and the inter-subject variation, and the degree of contribution to each of these variations is also investigated. It is verified through a numerical error analysis and a series of subjective listening tests that the PCs obtained from PCA of the CIPIC HR...