Abstract
Noise mitigation of stage machinery can be quite demanding and requires innovative solutions. In this work, an acoustic metamaterial capsule is proposed to reduce the noise emission of several stage machinery drive trains, while still allowing the ventilation required for cooling. The metamaterial capsule consists of c-shape meta-atoms, which have a simple structure that facilitates manufacturing. Two different metamaterial capsules are designed, simulated, manufactured, and experimentally validated that utilize an ultra-sparse and air-permeable reflective meta-grating. Both designs demonstrate transmission loss peaks that effectively suppress gear mesh noise or other narrow band noise sources. The ventilation by natural convection was numerically verified, and was shown to give adequate cooling, whereas a conventional sound capsule would lead to overheating. The noise spectra of three common stage machinery drive trains are numerically modelled, enabling one to design meta-gratings and determine their noise suppression performance. The results fulfill the stringent stage machinery noise limits, highlighting the benefit of using metamaterial capsules of simple c-shape structure.
Highlights
Noise control in mechanical and civil engineering requires compact, efficient, and low maintenance solutions
This is naturally challenging for stage machinery designers, especially when the constraints of the venue do not allow the application of conventional noise control measures, such as elastic bearings, noise barriers, or sound capsules
We investigated the reduction of noise emission from stage machinery using c-shape meta-atoms, with simple geometry that facilitates relatively easy manufacturing
Summary
Noise control in mechanical and civil engineering requires compact, efficient, and low maintenance solutions. The control of noise emitted by machinery operating in theaters or operas, such as stage elevator drive trains, is quite demanding, with the emission limits being as close as possible to that of the background noise levels.. The control of noise emitted by machinery operating in theaters or operas, such as stage elevator drive trains, is quite demanding, with the emission limits being as close as possible to that of the background noise levels.1–3 This is naturally challenging for stage machinery designers, especially when the constraints of the venue do not allow the application of conventional noise control measures, such as elastic bearings, noise barriers, or sound capsules. Since the stage machinery manufacturer is unable to influence the noise emission of the gearboxes directly, secondary noise control measures are required. Stage machinery is operated in intermittent periodic duty cycle S3 40%, which requires sufficient heat exchange by forced or natural convection. in this work a novel meta-capsule (acoustic metamaterial capsule) is introduced, which can overcome these drawbacks
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