Abstract
It is known that the sound-absorbing wedges can be simulated with a series of non-uniform electrical transmission lines which acts as an impedance-matching section between a lower impedance side (an open air) and a higher-impedance side (a wall). But, as the numerical calculations are too tedious to practice, the optimum design of wedges has been carried out almost experimentally and their essential aspect is left untouched. This paper describes the influence of the acoustical constants and size on the sound absorption characteristics of wedges, which is verified with an electric simulator and a standing wave tube. Each wedge element, such as a taper, a base and a space, is investigated separately. A tentative "trapezoid" wedge is also mentioned. The following results are obtained: (1)A similarity law holds good for sound-absorbing wedges as well as for the sound-absorbing layers. (2)The pointed head of wedge is not so effective that a flat head is possible. (3)An essential part of wedge is the wedge-shaped air cavity at the bottom of tapered section, a slight adjustment of which may change the characteristics appreciably. (4)The product of effective resistance r and total length l has an optimum value. (5)The ratio of the taper length to the total length has an optimum value. A wedge composed of a taper only may lose its absorptivity below a critical frequency.
