A Study of the Relationship between Head Related Transfer Functions and Elevations

Head Related Transfer Functions (HRTFs) are signal processing models that represent the transformations undergone by acoustic signals, as they travel from their source to the listener’s eardrums. The study of HRTFs is a rapidly growing area with potential uses in virtual environments, auditory displays, the entertainment industry, human-computer interface for the visually impaired, aircraft warning systems, etc. The positioning of the sound source plays a major role in the resonant frequency of the HRTFs. In this paper, we examine the effect of changing the elevations of these sources; we examine the effect on the first peak and the first notch of HRTFs. We use the HRTF database at FIU DSP lab. This database hosts the HRTFs from 15 subjects and their 3-D images of conchas. For each subject, the database contains the Head Related Impulse Responses (HRIRs) for the sound sources placed at six elevations (54°, 36°, 18°, 0°, -18° and -36°) and twelve azimuths (180°, 150°, 120°, 90°, 60°, 30°, 0°, -30°, -60°, -90°, -120° and -150°). A relationship between the first peak or notch and the elevation can help us model HRTFs mathematically. This can reduce the size of a HRTF database and can increase the speed of HRTF related computations