This research demonstrates the usage of numerical acoustics to model sound and vibrational energy propagation in HVAC ducts and plenums. Noise and vibration in HVAC systems propagates along three primary paths that can be classified as airborne direct, airborne indirect and structure-borne. The airborne direct path was simulated using acoustic FEM with special boundary conditions to handle the diffuse acoustic field loading and the baffled termination. The insertion loss for a number of different plenum geometries was compared to published measurement results. Results were in good agreement both below and above the cutoff frequency. Additionally, the airborne indirect path, often termed breakout noise by the HVAC community, was assessed using Statistical Energy Analysis (SEA). This path was examined experimentally by placing a loudspeaker inside the air handler and measuring the sound power transmitted through the walls. SEA results compared favorably with the measured results in one-third octave bands even at low frequencies. Finally, the structure-borne path was considered by exciting the walls of the aforementioned air handler using an electromagnetic shaker. The panel vibration and the sound power radiated from the panels were measured. Results were compared with the SEA with good agreement provided that SEA loss factors were determined experimentally.

This article focuses on computer noise analysis and noise reduction processing. With the popularity of computers, people are increasingly demanding the comfort of using computers. Solving the noise problem of the computer case can make the working environment more comfortable. People working in a noisy environment for a long time can cause anxiety and the quality of work is not high. The main purpose of this paper is to analyse the characteristics of computer noise and to reduce the noise of the chassis through the secondary sound source. Through the comparison of the experimental and simulation results, the noise reduction effect of the secondary sound source on the computer case is obtained. This paper can provide a scientific reference for the manufacture of computer chassis and improvement of noise.