Characteristics of Evacuation Guidance Sounds for the Visually-Impaired during Fire Alarms

Recently, various intelligent evacuation guidance systems that can be applied in buildings were studied. Technology development for the evacuation of vulnerable people such as the visually-impaired is necessary. Voice guidance is a method used to lead the visually-impaired toward the evacuation route. However, it is necessary to review whether it is possible to hear and understand the voice guidance during the sounding of fire alarms. In this study, simulations were conducted to predict the sound power level of the voice guidance device that can secure an acceptable sound transmission index of the guide sound and the appropriate distance from the voice guidance device, when a fire alarm sound is generated in a hallway space. The study found that an acceptable sound transmission index was achieved when the sound power level was 100 dB and the appropriate type of sound device was found to be a necklace-type headset or a regular headphone.

Trailing Edge Thickness Effect on Tonal Noise Emission Characteristics from Wind Turbine Blades

Broadband noise generation from wind turbine blades is one of the fundamental aspects of flow-induced noise. Besides the turbulent boundary layer flow over the blades, factors such as the angle of attack, the turbulence intensity, the trailing edge thickness of the blade and their shapes strongly influence the overall sound power levels at high frequencies, i.e. f > 8 kHz. In large operating wind farms, a trade-off between noise generation and power production is considered by power utility firms to maximize the return on investment (ROI) and minimize the fatigue damage on wind turbine components. The present work deals with the analysis of the thickness effect on trailing edge bluntness noise level at hub height average wind speeds of 7 m/s, 10 m/s. A semi-empirical BPM model was used to predict the sound pressure levels from the 37 m blade length of a 2MW wind turbine. The receiver configuration was fixed at a distance of 120 m from the source height of 80 m. The results demonstrated that as the trailing edge height increased from 0.1 % to 0.5 % of the local chord, the sound power level increased by ~ 17 dB for frequencies > 200 Hz, but decreased by 16 dB when the thickness is 0.1 % local chord. The computed results of the sound power level using the BPM model have been validated using experimental data and showed a good agreement for the tonal frequencies, f ~ 10 kHz, where the trailing edge bluntness noise becomes dominant.

Reducing the noise level of power transformers

The results of studies of the noise of power transformers at the enterprises of the machine-building complex are presented in this paper. The causes of the noise of power transformers are identified, the analysis is made, and the main design indicators affected the increase in the sound power level of high-voltage converters are determined. Based on the analysis of design indicators, organizational and technical measures are proposed for improving reliability and accident-free operation of power transformers, as well as reduction of the noise level of power transformers.

Potential noise annoyance from ambient air quality measurement using high volume air sampler (HVAS)

One of the benchmarks in air pollution is the quality of ambient air consisting of gas and particulate matter. Measurement of particulates in ambient air can be done using a High-Volume Air Sampler (HVAS). However, in the measurement process it sometimes causes noise annoyance to the community where the measuring instrument is operated, considering that the operating time of the instrument is 24 consecutive hours. This research identifies the value of the sound power level emitted from the several types of HVAS to the surrounding environment. There are two types of HVAS measured in this study consisting of one unit of HVAS with analogue flow control made by Indonesian manufacturer and two units of HVAS with digital flow control made by Japan and United States of America manufacturers. Sound power level is determined using ISO 9614 method with a sound intensity analyzer as the main instrument. The sound power level data for each HVAS were than compared and frequency spectrum distributions are evaluated. Based on the research results, it was found that some sample units emitted sound power levels of more than 90 dBA with dominant noise being at high frequencies starting from 4000 Hz. The results of the research can be used as an early information in the development of the HVAS regarding noise mitigation, because there is different approach for controlling noise specifics in low, mid and high frequencies noise source.

Statistical assessment of A-weighted sound power level for printer with electrophotographic engine

Statistical distribution and statistical upper limit (the value which 93.5 % of the batch of new equipment are expected to lie) of A-weighted sound power level for one office printer were experimentally estimated from 10 new samples picked up from market. The printer is capable of A4-size printing with electrophotographic engine which corresponds Annex C.16 Page printers in ECMA74 17th (2019). A-weighted sound power level for continuous printing mode was determined in accordance with noise test code for ITTE (Information Technology and Telecommunications Equipment such as printers and personal computers), ISO 7779:2018 and ECMA-74 Annex C. Sample standard distribution of production of overall A-weighted sound power level (determined from 100-10000 Hz one-third-octave band) is 0.25 dB, whereas individual one-third-octave band has larger distribution. The value obtained is better than reference distribution 1.32 dB set in ISO 9296:2017 which states estimation of statistical upper limit value of the batch of equipment for ITTE.

Round-robin testing on Sound power level measurement for Reference Sound Source and Office printer

Round-robin testing for two samples, Reference Sound Source in accordance with ISO 6926 and Office printer with electrophotographic engine, were executed by seven testing laboratories in Japan on 2020. All tests were executed with parallelepiped measurement surface in hemi anechoic chamber in accordance with testing standard for engineering-grade sound power determination, ISO 3744:2010. The results show that sample standard deviation for RSS is better than printer. Standard deviations for overall A-weighted sound power level for two samples are better than combined standard uncertainties calculated with reference example of standard deviations in ISO 3744 (1.5 dB for Reference Sound Source as standard deviation of operating/mounting condition is negligibly small, 1.6 dB for printer as stable operating/mounting condition 0.5 dB). This paper also indicates tips for those who would conduct round-robin testing to obtain valid results by obviating incorrect operations and malfunctions of printers or similar equipment from the experience of some round-robin tests.

Evaluation of floating floors performances using the reception plate method

This paper concerns the development and experimental validation of a simplified method to evaluate the performances of materials for floating floors. The method is based on the reception plate theory. The porpouse is to evaluate the impact sound pressure level reduction ΔL by the differences of the sound power level ΔP measured on the reception plate with and without the acoustic material. The results are compared with the values measured in accordance with ISO 10140 standards.

Road traffic noise mapping based on aerial photographs - sound power level determination of road vehicles

As the first step to obtain a city urban area noise map of road traffic noise, sound power levels of vehicles on the roads should be accurately estimated over a wide area. In Japan, ASJ RTN-Model 2018 was proposed as the representative road traffic noise prediction model, and by using the model sound power level of a vehicle can be determined if the vehicle type, traveling speed, and driving mode are known. As such data on urban road network, the Ministry of Land, Infrastructure and Transport of Japan publishes the road traffic census including road traffic volume and travel speed of major roads in Japan. The data, however, is limited to major roads and there is no data on minor roads. In this study, to estimate noise condition and situation on arbitrary road, a method for estimating the traveling speed and the traffic volume of vehicles on the road from aerial photographs was examined. Road traffic noise levels along several roads in Tokyo were analyzed by the proposed method and the validity of the calculation results were verified by comparing with short-time measurement results obtained along the target roads.

Measurement and Assessment on Environmental Noise Impact of Electric Vehicles in Accelerating Condition

Noise emission from the vehicles propelled by electric system (such as pure electric and hybrid electric vehicles, EVs) is usually lower than the conventional internal combustion engine vehicles. Some previous studies have been shown the difference in A-weighted sound power level of EVs from the conventional ones. The difference is not dramatically large, i.e. less than 4 dB when the cars running at constant speed of 20 km/h. In this paper, we present the additional measurement results of sound power level of EVs in accelerating condition. Because when the cars in accelerating condition, the difference of propulsion systems becomes more significant on noise emission. The results are shown as regression model of sound power level depending on the vehicle speed. Moreover, the environmental noise impact of growing population of EVs is assessed through a prediction of at a case of intersection.

Sound Intensity Mapping on Single Cylinder Direct Injection Diesel Engine with The Application of Palm Oil Methyl Ester Biodiesel

The utilisation of biodiesel nowadays has become familiar with rapid production types of biodiesel in order to replace the dependency on the fossil fuel parallel to the implementation of green technology that emphasises the products to be more environmental-friendly. Nevertheless, the emerges of various kinds of biodiesel cannot be simply used, despite using the biodiesel does not need any major modification on the engine; it still needs a few analyses that must be done to determine whether it will give advantages or disadvantages. Therefore, this research was carried out to investigate the effect of using palm oil methyl ester (POME) biodiesel on the engine in terms of noise emission. The sound intensity mapping method was used to indicate the effectiveness of the biodiesel by identifying the noise radiation. Along with the mapping, the sound power level (SPL) is also being obtained to provide a clear comparison between the parameters. Generally, switching up the engine speed and load increased the sound power level. Based on the results obtained related to the SPL, the intensity mapping tends to show a higher colour-coded in the noise source image for the higher engine speed and load setup. It was found that the engine speed and load give a significant contribution to noise emission produced by the engine, and it can be inferred that this method can be utilised to accomplish the noise emission analysis.