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Development of source-path models to synthesize product sounds of an outdoor HVAC unit.

Author(s) : LEPAK W.

Type of monograph: Master thesis

Summary

Outdoor heating, ventilating, and air-conditioning (HVAC) units emit a significant amount of noise, which may lead to poor sound quality and a perceived low product quality. It is the job of the noise control engineer to reduce the undesired noise and improve the sound quality of the outdoor HVAC unit to decrease consumer annoyance. There is great interest in developing a detailed and accurate acoustic model of the outdoor HVAC unit so that the sound of the outdoor HVAC unit can be listened to before the unit is constructed. Having an acoustic model which can synthesize sounds allows the noise control engineer to evaluate and improve the sound quality of the outdoor HVAC unit during the design process, without the need for extensive prototyping. Acoustical holography methods will be used to identify and localize noise due to the fan, and other significant noise sources, to visualize the sound field. In the current study, an acoustic model is described which can be used to model the noise due to structural radiation and vortex shedding of the outdoor HVAC unit’s rotating fan blades, one of the top contributors to the unit’s overall noise level. This moving source model simulates the Doppler effect which occurs when the blade moves towards and away from a receiver. The results from this moving source model is shown for different source signals, including sinusoidal, bandpass random, repeating random, and sinusoidal with time-varying frequency source signals. The parameters of this moving source model will be optimized to reproduce the experimental results, including the power spectral densities, tonal power component, and auralizations.

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Pages: 128 p.

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