Implementation of active noise cancelling for sound isolation box

Abstract

A quiet room is essential for acoustical instrument calibration, such as the sound level meter. A small acoustic chamber can be utilized to create an environment that is free from noise. Commonly, it is built with a passive noise-blocking system using high-density absorber material such as rock wool or glass wool. However, this approach results in a room that is both heavy and costly. This paper proposes a mini acoustic chamber that utilizes an active noise cancelling (ANC) system to block the noise. A filtered-x least mean square (FxLMS) algorithm was implemented for the ANC system. A simulation of the system with the recorded actual noise data was conducted to find the optimum filter parameter. The results show that the ANC system could reduce the noise up to 2 dB for certain types of noises. The sound outside the chamber was recorded and processed offline to tune the filter parameter. Evaluation of the effectiveness of the proposed noise reduction system was performed by measuring the sound inside the chamber.