Elimination of High-Frequency Whistle Noise in a Residential Ducted Air-Conditioning System Using a Dedicated Pipe Muffler Design

Abstract

This paper investigates the whistle noise issue of ducted air-conditioning units under high discharge pressure operating conditions. The high-frequency whistle noise source is identified within the pipe system through onsite experiments. Commonly used mufflers for vehicle engines and industrial ducts are found not suitable for air-conditioning pipe systems due to the high fluid velocity that goes through. A dedicated pipe muffler is then designed, and several design configurations are theoretically and experimentally tested. The muffler with the perforated inlet penetration pipe is found to have the best noise attenuation performance at high frequencies without sacrificing its noise reduction performance at low frequencies. The noise measurement results of the whole unit in both the anechoic room and on site confirm that the high-frequency whistle noise can be eliminated and the designed muffler can overall reduce the noise level and improve its sound quality metric-tonality level (TNR).