Stereo loudspeakers localize sound by summing signals to create interaural phase differences

Evidence

Blumlein showed that the coherent addition of the acoustic signals arriving at the ears from both loudspeakers, as shown in Figure 7.1, produced a phase shift that mimicked the effect of the interaural time delay cue. In essence the signals from both speakers arrive at both ears, with equal amplitudes, because at low frequencies, they diffract easily around the head. Due to the relative delay caused by the speaker angles, the sine waves from the contralateral (farther away) speaker are delayed with respect to the ipsilateral (closer) one. As we know from Chapter 1, in Section 1.3.1, adding two sine waves of different amplitudes and phase forms a single one with a different amplitude and phase. The resultant phase of the these combined sine waves at the two ears will be a function of the relative speaker amplitudes. Blumlein showed that this mimics the effect of the ITD cue. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2196

Categorization

• XREF: Connects to the earlier chapter sections on interaural time delay (Chapter 1, 1.3.1) and head shading above 1 kHz (2.6.2) that this passage explicitly builds on.