A transducer’s physical size relative to wavelength determines its directivity.

Evidence

This appendix has presented the basic Fourier relationship between the far-field polar response and the near-field illumination of the aperture. It has demonstrated its utility in a variety of electroacoustic applications. In particular, it is possible to derive some useful relationships between the size of the speaker, with respect to wavelength, and its directivity performance versus frequency—in particular that for directivity, size really does matter! — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2946

Categorization

• XREF: Connects directly to the earlier retained passages on directivity increasing with frequency (ka / size-to-wavelength ratios), pulling the appendix’s practical relationships back to chapter 0’s physics.