Abstract:
Noise pollution is a serious concern due to its adverse effects on safety and health. Prolonged exposure to excessive noise leads to noise-induced hearing loss. Effective solutions provide minimum layers of protection. This research investigated the performance of an active noise control method as a noise-induced hearing loss intervention for a 1500cc Variable Valve Timing with Intelligence (VVT-i) gasoline internal combustion engine. Autodesk Inventor and ANSYS were used for design, modelling and simulation of the prototype. Key design parameters included the length, diameter, and a continuous inclined barrier internal geometry configuration. Quantitative performance testing of insertion and transmission losses, and noise profile characteristics was done using an integrating sound level meter. Results obtained were used to evaluate the performance of the muffler design solution, quantification of residual noise hazards, and development of measures to address residual noise hazards. The engine noise characteristic was broadband, with noise levels in the lower frequencies exceeding 100dB(A) (f=2.769, p=0.0088). Critical frequencies affecting hearing occurred between 33.5 and 2,000 hertz. Unmuffed engine noise exceeded the upper action limit of 85 dB(A), making it unsuitable for operation in both industrial setups and silent zones. A 50mm pitch continuous inclined barrier in a simple expansion chamber design solution exhibited noise levels between 60 and 80 dB(A) (f=23.713, p=6.5E-22) with a maximum of 90dB(A) at 4kHz. Residual noise from the design solution may be addressed by locating the receiver at 10m from the source, or providing a low-grade hearing protective equipment rating of 20dB(A). The design can be used as a noise-induced hearing loss intervention where elimination of the hazard is not feasible. Further investigation should be done to establish the minimum design configuration that would provide the maximum sound attenuation. In addition, further research could be carried out to determine the performance of the continuous inclined barrier solution at the lower and higher frequencies respectively.
