Research on Comprehensive Evaluation Method of Transformer Noise Based on AHP Matter Element Model

Aiming at the problem of transformer condition evaluation, a comprehensive evaluation system for transformer noise is constructed according to the mechanism of transformer noise generation and propagation. Using matter-element theory and AHP, a state analysis method for transformer noise evaluation based on AHP matter-element model is proposed. The case analysis proves that the method is feasible for non-contact evaluation of transformer faults, and can accurately evaluate the state of the transformer, providing guidance for the operation and maintenance of the transformer.

Test and Research on Noise Distribution Characteristics of 220kV Oil-immersed Transformer

Large power transformer is the main noise source of substation. With the increase of voltage grade and rated capacity, the noise radiation value of power equipment continues to increase, which has a great influence on the noise standard of substation boundary. In this paper, two test conditions of no-load voltage and load current are considered. The transformer noise testing datum is constructed. The distribution law of factory noise SPL of 220kV oil-immersed transformer is obtained. The test results provide accurate test data for transformer factory noise evaluation.

Psychoacoustic evaluation of internal combustion engine noises

When buying a car, the acoustic impression of quality of a vehicle drive train is becoming more and more relevant. The perceived sound quality of the engine unit plays a key role here. Due to the nature of individual background noises, that sound quality is negatively influenced. These noise components, which are perceived as unpleasant, need to be further reduced in the course of vehicle development with the identification and evaluation of disruptive noise components in the overall engine noise being a prerequisite for effective acoustics optimization. In particular, the pulsed ticker noise is classified as particularly annoying in Otto DI engines, which is why this article aims to analyze and evaluate the ticking noise components from the overall noise. For this purpose, an empirical formula was developed which can classify the ticking noise components in terms of their intensity. This is purely perception-based and consists of the impulsiveness, the loudness and the sharpness of the overall engine noise. As with other psychoacoustic evaluation scales, the rating was made from 1 (very ticking) to 10 (not ticking). The ticker noise evaluation formula was then verified on the basis of hearing tests with the help of a jury of experts. According to this, it can be predicted precisely in which engine map areas the ticker noise undermines the pleasantness of the overall engine noise.

Analysis of the characteristics of noise from substations in buildings

The urbanization has resulted in an increasing number of transformer stations, which has resulted insignificant building noise problems. However, noise problems persist because of inadequate noise characterization and the use of imperfect noise evaluation indexes for centralized substations. Based on this problem, a transformer vibration noise coupling analysis method based on empirical mode decomposition (EMD) and spectrum analysis is proposed in this study. The proposed method accurately and effectively screens and characterizes transformer noise and provides a theoretical basis for transformer noise reduction. To verify the effectiveness of the proposed method, a transformer was reconstructed as an example. It was found that the low-frequency noise from the transformer was mainly caused by vibrations with a frequency below 500 Hz, particularly frequencies of 300 Hz and 100 Hz and 50 Hz. Through the calculation and analysis of eigenvalues, the noise reduction measures focusing on vibration reduction were proposed. In the end, a noise reduction of 10 dB was achieved, which meets the comfort requirements. This method can accurately and effectively identify the characteristics of transformer noise, which makes up for the insufficiency of transformer characteristics analysis in the past. Provide guidance for perfecting transformer noise evaluation index. Practical implication: The noise problem caused by substations is getting more and more serious. Conventional noise detection and noise reduction methods can no longer meet people’s requirements for sound comfort. The coupling analysis method of vibration and noise based on EMD and spectrum analysis proposed in this study can effectively extract the characteristics of transformer noise. It provides theoretical support for the noise reduction transformation of transformers, and solves the problem that the current engineering noise reduction transformation has no theoretical basis. Noise characteristic analysis can make up for the shortcomings of existing acoustic comfort indicators that only use sound pressure level as the evaluation indicator.

Power generator noise evaluation considering conversation audibility and improvement

Compact power generators are useful and convenient tools all over the world. The products are mainly set at around living space of human. Hence, the radiated noise should not disturb the human activities such as conversation. In this study, we then focused on the ease of conversation as the power generator noise performance and attempted to improve the performance. We firstly carried out subjective evaluate tests using recorded generator noise samples and reproduced Japanese syllables to evaluate the performance quantitatively from sound pressure of power generator noise. In the test, the participants answered the syllable they heard under the reproduced generator noise condition. And the correct answer rate of the presented syllable was calculated in each generator noise. The correct answer rate could be expressed well by using articulation index (AI) of each generator noise. Subsequently, the noise reduction target level of a portable generator satisfying the rate at 80% was set in each frequency band considering the influence of each frequency band on AI. Noise countermeasure was carried out to intake and exhaust parts having large contribution at the reduction target frequency bands. Finally, the noise could be decreased well and the AI cleared the target level.

Annoyance evaluation of noise emitted by urban substation

In China, noise pollution from substations in urban areas is becoming more and more serious. An annoyance evaluation of the noise emitted by urban substations is presented. First, the subjective evaluation is conducted on the noise samples from urban substations via the semantic differential method. Subsequently, according to the typical characteristics of urban substation noise, 14 acoustical metrics are used to describe the noise samples for objective evaluation. Then the correlation analysis and regression analysis between the objective and subjective evaluation results are carried out. Finally, a regression model for urban substation noise evaluation is established. Practical application shows that the regression model can correctly predict the subjective annoyance of urban substation noise.