Predicting speech intelligibility in rooms from the modulation transfer function III Mirror image computer model applied to pyramidal rooms
article
The effect of applying oblique walls, or oblique panels attached to the walls, is studied for a square room with a variable angle between the walls and the floor (truncated pyramid). The Modulation Transfer Function (MTF) for any speaker-listener pair can be calculated as the vectorial sum of the direct sound and the contributions of all virtual sound sources. From this MTF the Speech Transmission Index (STI) can be derived, which correlates highly with the intelligibility score for words and sentences. First the method for finding the coordinates of the virtual sound sources for the general case of a room with non-parallel boundary planes (geometrically perfectly reflecting walls and ceiling, totally sound-absorbing floor) is explained. On this basis the case of a room shaped as a truncated pyramid is considered. The considerable improvement in speech intelligibility obtained by tilting the walls is illustrated for a room of (15 multiplied by 15)m**2.
TNO Identifier
5422
Source
Acustica, 48(5), pp. 320-324.
Pages
320-324
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