Session: 01-02-01: Passive, Semi-Active, and Active Noise and Vibration Control

Paper Number: 112362

112362 - On the Reduction of the HVAC Noise Using Active and Passive Noise Control Technologies 

In the study, we aimed to develop the active and passive noise control techniques for the reduction of the flow-induced noise generated and emitted from Heating, Ventilation and Air conditioning (HVAC) system in a vehicle cabin. As the HVAC system employ dynamic processes to maintain thermal comfort it creates many unwanted noises which lower the acoustic comfort. The purpose of this study was to decrease the low frequency noises (35 - 150 Hz) of an air conditioner to employ an active noise control (ANC) which was built with a frequency-domain gradient descent algorithms (FDGD) to adapt the weighted filter. In addition, porous materials that allowed sound transmission and restricted fluid flow to reduce the flow-induced noise (150 – 550 Hz) generated by objects in flow was attached in the air intake of the flow exit of HVAC system. In the experiment, an air conditioner noise was measured by a microphone which was set near driver’s left ear and referenced by a microphone set near the map lamp for ANC. A high-speed camera and laser light source were set in the vehicle cabin. Oil mist generated by an oil mist generator and compressor was put in through the HVAC air intake and the movement of the mist was filmed to confirm the change in flow with and without porous materials. First, we conducted the experiment to confirm the reduction effect of ANC. Measurement result shows that in the 1/3 -octave band frequency-domain, the sound pressure level was 7.2 dB smaller at maximum. It was also found that the noise in the 35 - 150 Hz frequency band could be reduced and its reduction effect was 4.7 dB on average. It was caused by the high coherence between the microphone signal at the map lamp and the microphone signal at driver’s left ear position. In addition, our algorithm had high convergence and stability that was caused by dynamic control of the step size parameter and the addition of new coefficients. Next, visualization and PIV analysis of the flow at the exit of HVAC system were also conducted to confirm the changes in the flow velocity and turbulent intensity by employing porous materials. Visualization and PIV analysis results show that the turbulence in the flow was reduced and the flow velocity increased, confirming the improved airflow efficiency. The result that was measured by microphone at driver’s left ear shows that overall noise above 150 Hz was reduced by more than 3 dB. This is thought to be due to reduced flow turbulence at the exit of the HVAC system. Combining the ANC and the porous materials would reduce the HVAC noise over a wide frequency range.

Presenting Author: Koki Shige Toyama Prefectural University

Presenting Author Biography: Koki Shige received the B.E. degree from Toyama Prefectural University Japan, in 2022. He is now in the graduate school of Mechanical Systems Engineering in Toyama Prefectural University. His main areas of research interest are Active and passive noise control for HVAC noises. He is a member of the Society of Automotive Engineers of Japan and the Japan Society of Mechanical Engineers.

Authors:

Koki Shige Toyama Prefectural University
Osamu Terashima Toyama Prefectural University