Abstract:

The property of ``directional tone color,'' especially characteristic of a violin [G. Weinreich, J. Acoust. Soc. Am. 101 (to be published)], consists of a directional radiation pattern which is a very strong function both of angle and of frequency. This can produce the illusion that each note (in fact, each harmonic of each note) is coming from a different direction, confusing the common psychoacoustic cues and endowing the sound with a specially striking spatial sense. A loudspeaker has been constructed in which a single driver drives four pipes of different lengths, with their mouths forming a three-dimensional pattern of roughly 20-cm spacing. This produces four sources whose phases vary rapidly with frequency, and which interfere with each other so as to produce the type of pattern desired. The result (which will be demonstrated), when driven by a monophonic signal, appears to ``fill space'' more strikingly than many stereo systems. The paper will also discuss other ways in which the effect might be produced (for example, by using a number of drivers with varying signal delays), various applications (in particular, for pipe organ music), and implications for the way in which stereo music is perceived. [Work supported by NSF.]