抄録
This paper discusses a method of reducing sound pressure level in mail processing machines at low cost. Based on sound-reflective and reverberative characteristics of a stack part of mail processing machine, we have reduced sound pressure level by opening back side of a stack part. Reduced sound pressure level at an evaluation point is examined by a model with a front and a back opening which has a trade-off between decreasing internal sound and increasing diffracted sound. We have applied this method to a stack part of mail processing machine, and experimental value roughly corresponded to calculated value. The reduced sound pressure level of a slit-like back opening was 3dB under white noise, and it had the same effect as a sound-absorption material.
