0.5 3-d sound implementation

We employed the head-related transfer functions (HRTFs) measured by Bill Gardner and Keith Martin at the MIT Media Lab to implement the 3-D sound effect. Gardner and Martin determined the left and right ear impulse response from a Realistic Optimus Pro7 loudspeaker mounted 1.4 meters from a KEMAR dummy head microphone at a sampling rate of 44.1 KHz.

Additionally, we used the compact data file package published on their website, which included a data-reduced set of 128 point symmetrical HRTFs derived from the left-ear responses. Because of symmetry, the right-ear responses can be derived from the left-ear responses. Measurements were made at elevations from -40 degrees to +90 degrees and at azimuth from 0 to 180. More detail on HRTFs measurements can be found at:

http://sound.media.mit.edu/resources/KEMAR/hrtfdoc.txt

Utilizing Gardner and Martin’s HRTFs, we built the following system in Matlab to synthesize a 3-D sound.

At an elevation of 0 degrees and an azimuth of 80 degrees, the impulse responses of the two systems above are shown in figure 2 and 3.

For those who love mathematics, Corey I. Cheng and Gregory H. Wakefield provided a complete mathematical derivation of head-related transfer functions in their paper Introduction to Head-Related Transfer Functions(HRTFs): Representations of HRTFs in Time, Frequency, and Space.