Doppler shift becomes very important when sound sources move. Furthermore, doppler shifts cannot be simulated by any method put forward so far (Blauert 390). Doppler shift is caused by a sound source moving closer to or farther away from the listener, and results in a shift of spectrum. Again, it is important that the listener be familiar with the sound in order to percieve this shifted spectrum. However, if a sound source is traveling past a listener, he will hear a range of doppler shifts, from a positive shift (higher pitch) to a negative shift (lower pitch). This combined with changing sound level will enhance the localization of any sound, and give the listener understanding of where the sound will be in succeeding moments.
The following is a doppler - shifted bassoon note, traveling in front of the listener
Bassoon travelling past listenerVisual perception of a sound source can greatly influence, or even override auditory perception. If a sound source is displaced from where it is visually percieved, the brain will "correct" the auditory perception and the sound will be percieved as coming from the visually percieved source. An example comes from watching television: although the speaker for a monophonic television may be on the side of the TV, watchers will still percieve the speeh heard to be coming from the images percieved on the screen (Blauert 193).
Other theories have been proposed that have recieved little support. These include bone conduction and tactile theories. It has been shown that attenuation of sound entering the skull via bone conduction (not through the ear) is at least 40 Db (Blauert 192). The influence of tactile information has been proven small by showing that if the outer ear, or other part of the body is anesthetized, it does not impede sound localization (Blauert 200).