Processing and Unification of Environmental Noise Data from Road Traffic with Spatial Dimension Collected through Mobile Phones

Noise measurement using mobile phones is now developed very well. While there are some good applications for the measurement of noise from road traffic, thus on processing of measured data is only paid a very little attention. The data, however, are burdened by specific errors and for further work with them it is necessary to adjust and determine their uncertainty. One of the biggest problems is inaccuracy in position versus the noise source and the shortest length of measurement that can be regarded as representative. Imprecision in terms of location can be determined by calculating the variance of possible distance from the noise source, which for measurement of traffic noise requires a map-matching data points both transverse to the street (sidewalk) network and in the longwise direction. During typical urban measurements, this error can even reach 7 - 10 dB. Three basic types of algorithms for the calculation of uncertainty and positional correction based on the type of input and output data (raster, vector, vector-oriented) were tested. Uncertainty in the variability of the measurement data is necessary to determine from the number of passing vehicles per time unit. The presented solutions are implemented in the Mobile Noise system.

Environmental noise beside an elevated box girder bridge for urban rail transit

Noise generated by trains running on elevated lines creates many disturbances to the normal lives of surrounding residents. Investigations have shown that people living along elevated lines complain that the noise is sometimes unbearable. To better control the noise and optimize the acoustic environment, noise spectrum characteristics were analyzed and compared with a field test and a numerical simulation. Through an energy analysis of the noise on the bridge side, the energy distribution characteristics of the noise at specific measuring points in different frequency bands were obtained. The influence of the Doppler effect on frequency shift was analyzed. Based on the partial coherence theory, a multi-input and single-output program was compiled to calculate the correlation and contribution degree of the bridge structure-borne noise and wheel/rail noise at the one-third octave center frequency. The results show that the peak noises of the bridge and the wheel/rail are concentrated at 31.5–63 Hz and 400–800 Hz, respectively. For environmental noise on the bridge side, the frequency band above 250 Hz is mainly affected by the wheel/rail noise. In areas of noise source strength, the relative ratio of noise energy above 250 Hz can reach 83.4%. Noise in the near ground and far bridge area is mainly low-frequency, and the relative energy ratio is about 8.9%. The Doppler effect has an influence of less than 6% on the frequency shift with a speed of 67.9 km/h. In the low-frequency band below 250 Hz, the noise in the acoustic shadow area near the bridge and the ground is mainly contributed to by the vibration-radiated noise of the bridge, of which the contribution of the bottom panel is the most prominent. The noise in the comprehensive noise area of the far bridge is mainly caused by the structure-borne noise of the bridge, and the contribution of each bridge panel is different. This study can provide a reference for finding the source of elevated rail noise in some challenging frequency ranges and for then determining optimal designs and measures for noise reduction.

Noise Exposure Levels in Basic School Environments in a City in Ghana

Basic schools that are located in heavily populated residential and commercial areas in Ghana are exposed to environmental noise that can have detrimental effects on the academic attainments of children. Limited studies have been conducted on noise level in basic schools to date in Ghana. The objective of the study was to assess noise levels in and around learning spaces in basic schools in Ghana with a focus on Kumasi. A survey employing the use of interviews and an empirical monitoring of noise levels in and around learning spaces in four selected basic schools were adopted. The study revealed that mean outdoor and indoor noise levels exceed the World Health Organisation permissible limits by 30 - 40 percent and 90 - 107 percent respectively for schools in the commercial zones and schools that are located near highways. The school that is sited in an educational environment with a setback from the highway attained mean noise levels ranging from 1.2 percent below to 3.7 percent above the permissible limits for outdoor and between 64 - 105 percent for indoor. The outcome of the study is expected to engender the design of environmental noise resilient buildings to facilitate teaching and learning in basic schools in Ghana.

Influence of the sparsity of random speckle illumination on ghost imaging in a noise environment

The influence of the sparsity of random speckle illumination on traditional ghost imaging(GI) and GI via sparsity constraint(GISC) in a noise environment is investigated. The experiments demonstrate that both GI and GISC obtain their best imaging quality when the sparsity of random speckle illumination is 0.5, which is also explained by some parameters such as detection of the signal to noise ratio and mutual coherence of the measurement matrix.