カーテンによる木材加工場の騒音音場処理の一実験

Abstract

Previously, we reported that the sound radiated in an ordinary woodworking shop sometimes creates a non-uniform field of sound pressure. For example, the sound radiated from a woodworking machine such as a single surface planer has low frequency noise components, and produce an interference pattern in the test region. The interference between the direct sound wave from the source and the reflected sound wave from the boundary wall causes errors in evaluating the sound power of a machine considered. To eliminate this, a new measuring space having a volume of 27m3 and a surface area of 54m2 was constructed with two types of cloth curtains. This space is thought to be small for the measurement of radiated sound pressure, but can be constructed easily and cheaply. Although several wall conditions of boundary curtains were tried using an isotropic sound source fed with random noise, it was not possible to get an effective result about the distribution of sound pressure levels in this new space. For the router machine noise, however, the distribution of sound pressure level inside of this space was rather uniform than in the original space. Besides, no interference pattern was noticed in this new space tested.