DAFX: Digital Audio Effects, Second Edition

5.4 Binaural Techniques in Spatial Audio

Binaural techniques are loosely defined to be methods which aim to control directly the sound in the ear canals to match a recorded real case or with a simulated virtual case. This is done by careful binaural recordings, or by utilizing measured or modeled head-related transfer functions (HRTFs) and acoustical modeling of the listening space.

5.4.1 Listening to Binaural Recordings with Headphones

The basic technique is to reproduce a recorded binaural sound-track with headphones. The recording is made by inserting miniature microphones in to the ear canals of a real human listener, or by using a manikin with microphones in the ears [Bla97]. This recording is reproduced by playing the recorded signals in the ears of the listener. This is a very simple technique in principle, and can provide effective results. A simple implementation is to replace the transducers of in-ear headphones with insert miniature microphones, to use a portable audio recorder to record the sounds of the surroundings, and to play back the sound with headphones. Already without any equalization, a nice spatial effect is achieved, as the left–right directions of the sound sources and reverberant sound field are reproduced naturally. Especially, if the person who did the recording is listening, the effect can be striking.

Unfortunately, there are also problems with the technique. The sound may appear colored, the perceived directions move from front to back, and everything ...