Head-related transfer functions spatially pan monaural sources by modeling each ear’s directional filter response

Evidence

This type of processing is required in virtual-reality systems, in which sound sources need to remain associated with their visual cue. One way of achieving this is to measure the effective filter response to the two ears for different directions, as shown in Figure 7.14. These are known as head related transfer functions (HRTFs). These filter functions can then be used directly to “pan” a monaural source to a particular direction in the binaural stereo perspective. Because it is difficult to interpolate between HRTFs for different angles, these functions have to be stored as a large table of data in both azimuth and elevation. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2250

The HRTF can be thought of as the ratio of the frequency response of the input sound pressure at an ear canal to the frequency response of the input sound without the listener present. The HRTF can also be found as the head-related impulse response or HRIR such that the Fourier transform (see Appendix 1) of the HRIR gives the HRTF. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 737

Categorization

• DEFINE: Clearly defines HRTF as taking audio content into an acoustic download link, describing the filter response measured to the two ears for different directions.
• XREF: Connects to virtual-reality spatial audio design and to the binaural listening themes developed across the reader’s acoustics reading list. — connects to: Head and pinna scattering imprint direction-dependent spectral notches onto the ear signal. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1451
• corroborated: 2 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2250; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 737