In the development of binaural audio systems, the time-of-flight, frequency and level differences of the sound reaching the human ear play a crucial role. The influence of these parameters is referred to as the Head Related Transfer Function (HRTF).
The HRTF functions refer to the sound that reaches the ear directly or indirectly as reflected sound from walls, ceilings, and furniture. The brain also evaluates reflected, diffuse sound, as well as the sound sensation produced by turning, lowering, or raising the head. All sound waves, direct, indirect, reflected and diffuse determine binaural hearing.
The HRTF technique is also used in sound retrieval systems( SRS), among other applications. In this technique, a comprehensive sound field is generated via two loudspeakers, giving the listener the impression of spatial reproduction with the possibility of locating individual instruments.