[en] A device proposed for use in multiblade rip saws reduces the operational noise and hence minimizes operator injury.

[en] A transformer manufacturer (Pauwels International in Mechelen, Belgium) and an automation firm (Simac Techniek in Veldhoven, Netherlands) developed a fast and simple method to measure the sound pressure of transformers, based on the method 'Triggered Intensity', part of the IEC-551 guideline. 5 figs

[en] The title invention concerns a wind turbine with a rotor, consisting of a number of blades, each with a front edge and an irregular shaped (sawtooth) back edge. This wind turbine aims at reducing the noise pollution of wind turbines. 1 fig

[en] This paper proposes a simple criterion for noise limitation of wind turbines: 'The La_A50 from a Wind Farm should not exceeding the L_A50 of the wind generated background plus 5dB at any place of potential complaint'. This criterion is then examined and developed in the light of experience to date with turbine noise complaint and procedures. (author)

[en] Wind turbine noise generation mechanisms are essentially equivalent to the aero-acoustic mechanisms of other rotors, which have been studied in depth for many years. Basic sources for the wind turbine noise radiation process are defined, and their significance assessed. From the analysis, areas of potential improvement in wind turbine noise prediction are defined. Suggestions are made for approaches to wind turbine noise control which separate the noise problems at cut-in from those at rated power. Some of these offer the possibility of noise reduction without unfavourable effects on performance. (author)

[en] Wind turbine noise generation mechanisms are essentially equivalent to the aero-acoustic mechanisms of other rotors, which have been studied in depth for many years. Basic sources for the wind turbine noise radiation process are defined, and their significance assessed. From the analysis, areas of potential improvement in wind turbine noise prediction are defined. Suggestions are made for approaches to wind turbine noise control which separate the noise problems at cut-in from those at rated power. Some of these offer the possibility of noise reduction without unfavourable effects on performance. (author)

[en] Annoyance rating is important, but more important still is agreement on techniques for formulating minimal complaint criteria for design and specification purposes thus integrating noise control into the plant at the outset. A minimal complaint design criteria is suggested that finds its origin in the logic and techniques used successfully over many years for a wide range of power plant and other installations. The criterion is based on the masking of the wind turbine noise by the wind generated background noise. Satisfactory use of the criterion depends on the specification of inaudibility for the tones generated by the mechanical plant. Wind turbines generate more drive train noise than is realized and this contains many tones which tend to characterize the noise. Reduction of drive train noise would not only reduce the overall noise level but also give it a more acceptable character providing a margin against complaint in unusual circumstances of propagation. This requires very careful design of noise and vibration control in individual components. Vibration isolation between the support structures and the nacelle also requires careful attention. (UK)

[en] Community annoyance due to noise from wind turbines is often the result of noise character rather than level. Although the overall contributions from each of the two main classes of noise source, namely aerodynamic and mechanical, are often of a similar order for an untreated turbine, it is usually the mechanical sources which provide the dominant noise characteristics that may lead to annoyance. In this paper, the sources of mechanical noise are identified primarily with reference to horizontal axis wind turbines and then attention is concentrated on the rotor-shaft step-up gearbox, which is normally the top-ranking source. The major gearbox noise mechanisms and transmission paths are discussed and reference made to Noise Specifications and procedures applicable to the gearbox prior to its installation. The reduction of machinery noise is reviewed both at source and by treatment of transmission paths. (author)

[en] This research studies the reduction and the estimation of the noise level within a redundant configuration of low-cost (MEMS-type) inertial measurement units (IMUs). Firstly, independent observations between units and sensors are assumed and the theoretical decrease in the system noise level is analyzed in an experiment with four MEMS-IMU triads. Then, more complex scenarios are presented in which the noise level can vary in time and for each sensor. A statistical method employed for studying the volatility of financial markets (GARCH) is adapted and tested for the usage with inertial data. This paper demonstrates experimentally and through simulations the benefit of direct noise estimation in redundant IMU setups

[en] Kyndby windfarm has for a 4 year period suffered from noise problems where gear vibrations have been transmitted to the structure and been emitted with a high pure tone component. This paper describes the process from the registration of the first noise problems through all the problems with manufacturing of the correct gears and to the end where the final results were measured with satisfactory results. (au)