Читать книгу Engineering Acoustics - Malcolm J. Crocker - Страница 112

The directivity index DI is just a logarithmic version of the directivity factor Q. It is expressed in decibels.

A directivity index DI_θ,ϕ may be defined, where

(3.59)

(3.60)

Note if the source power remains the same when it is put on a hard rigid infinite surface Q(θ, ϕ) = 2 and DI(θ, ϕ) = 3 dB.