3pAA1. The influence of directivity on sound heard by an audience during an orchestral performance.

Session: Wednesday Afternoon, May 15

Time: 2:05

Author: Jurgen Meyer
Location: Phys.--Tech. Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany


For a listener seated in a hall, sound impressions are created by the time structure and the intensity ratios of direct sound, early reflections, and reverberation. The intensity ratios between these components depend on the directivity of the sound generated by different instruments. Even for high-pitched instruments, omnidirectional radiation is found only at frequencies below 500 Hz. The strength of the directivity can be described by the statistical directivity factor which fixes the angle-dependent reverberation radius of a source sounding in a hall. For directions of main radiation at upper string frequencies it is of the order of 2--3; for the woodwinds, it is a little lower; for the brasses it exceeds 4. Directions of strong radiation oriented toward the sidewalls, thus supporting the space impression, are found with the strings, bassoons, horns, and trombones. High-frequency components of strings are radiated in strong measure against the ceiling: These reflections support the brilliancy. These sound effects will be demonstrated with a real orchestra.

from ASA 131st Meeting, Indianapolis, May 1996