Auralization of psychoacoustic phenomena

Psychoacoustics deals with descriptions of the relationship between acoustic stimuli and auditory sensations. The acoustic stimulus is strictly speaking, the pressure waveform at each ear drum. In most cases, however, it is assumed that it is equivalent to a voltage wave­form at the terminals of a set of headphones, which are used for almost all psychoacoustic experiments. Only for studies on spatial perception and localization, free-field stimulation in an anechoic room is necessary, or, as has become possible in recent years, use can be made of simulated free-field situations through headphones. In some situations, however, one is forced to use loudspeaker sound reproduction under conditions where the use of headphones would be preferred, e.g. in classroom demonstrations of psychoacoustic effects. We will review some cases where the effect to be shown is artificially enhanced by the use of loudspeakers, some cases where the effect is mostly lost, and some cases where against all expectations things work out equally well as they would with headphones.