Microphone array for noisesource detection usually consists of two straight arrays arranged in cross or X shape. When multiple noise sources of nearly same levels are present, however, 2 arrays systems often show “ghosts” of the real source images. Three straight arrays are arranged here with the crossing angle of 60 degrees each other, named as “Star- array” in order to avoid the ghosts. Numerical simulation and experimental study for both stationary and moving noise sources proved that newly developed Star-array depressed the ghosts down to non-detectable level.
ABSTRACT: Reducing sound pressure levels (SPL) from a noisesource for improved acoustical quality in terms of speech intelligibility is the principal goal in multi-functional spaces. Speech intelligibility index (STI) calculated in noise is ‘STI in noise’, which is a quality indicator in multi-functional rooms. Screens blocking the direct sound from the noisesource provides a good improvement in ‘STI in noise’ by reducing noise levels . This paper discusses the impact of design parameters of screens to reduce noise levels. The parameters effecting the acoustical performance of screens are discussed together with the architectural constraints. Screen parameters such as position, height, bottom gaps, absorption capacity, depth, width are investigated together with the space parameters such as absorptive ceiling and floor.
Noisesource data is usually a problem. Road traffic data is not commonly available for all roads with the quality (types of vehicles, time representativeness, and accuracy) and quantity (different road segments) required. The maps described here required that a large number of traffic counts were performed both by the municipalities and by our technical team. Air traffic data was obtained from the airport authorities based on radar data and pre-defined air paths and routes. Railway data included results from a large program of measurements of noise emissions of rail equipment and from a prediction program FERR+ developed by the CAPS-IST Acoustics Group in recent years. Noise emission data from industry, leisure or other similar areas was obtained from measurement. The surveys were carried out in different times of the year, as necessary, to account for seasonal differences.
In the following example, a 10mx10m initial grid has been chosen to make a noise map (Figure 6, top right). After one iteration, the addition of 7% receivers (from 5765 to 6173), improves results in most areas of the map (colored area in Figure 6, bottom right). This improvement is only significant in relation to the refinement gained at the location of the isolines (Figure 6, left) and the enhancement produced in their standard uncertainty (Figure 7). Uncertainty of the lines placed closer to the noisesource has been enhanced notably (up to 3dB), unlike farther away lines, which see an improvement of less than 0.5 dB.
Geometrical approaches can deal efficiently with outdoor sound propagation problems whereas integral representations can represent coupled vibro-acoustic problems. The GRIM approach has been presented in several papers and conferences [1,2,4] and an original field of application is considered in this paper. Applying the GRIM method to sound insulation problems consists in using, in the integral representation of an acoustical field, a complex Green function which is computed by means of a ray tracing program or the like. If we consider the case of an outdoor noisesource at position S and a receiver point M inside a dwelling we first consider the reciprocal problem and write that the pressure at S due to a source at M can be written as:
In the case of a noise propagation experiment using a single point source, the location of the noisesource and the receiving point are fixed. Therefore, the favorable wind direction is easily determined. In case of a line source such as simple straight road, a line perpendicular to the source always represents the favorable wind direction. In the current case, the favorable wind direction is not easily established, because the road is of a complex structure and the ground is uneven. In order to determine the favorable wind direction, the correlation between the vector wind ( U vec ) and the average noise level per one light vehicle (L Aeq,10min,s ) was calculated under
In many countries the noise radiation is still the major limitation in the tremendous development of wind energy over the last years. Within several European research projects, modifications of the rotor blade trailing edge (sharp or serrated) and the tip design (avoiding tip vortex-trailing edge interaction by ´trailing edge cutting´) resulted in considerable noise reductions in the range of several dB. Mechanical noise from gear box and generator was reduced significantly but tonal noise is still the crucial point concerning the acceptance of wind turbines. The measurement procedures have been improved significantly as well. The IEC standard 61400-11 Wind Turbines – Part 11 ‚Acoustic Noise Measurement Techniques‘ was revised recently in order to present a procedure expected to provide accurate results that can be replicated by others.
Figure 3.6 constitutes the portray of deterministic frequency combs in the detuning regime this thesis discusses; α ∈ [0, 3]. The effect of stochastic terms, introduced in section [2.3], into the deter- ministic solutions, altogether with the previous information, is analyzed in this section. Therefore the new problem now consists in solving the dynamical system LLE + stochastic term, under the initial condition given as a fully grown stationary deterministic frequency comb. The proccedure is evolving the new pattern until it achieves the stationary state. Considering a stochastic LLE equation, the mathematical treatment from section (2.2) is not valid anymore and we are dealing with a different scenario for each different noise scheme. That is the reason new solutions will not start from an homogeneous plus small fluctuations background. If in addition the noise amplitude is of low intensity, this let us to study the effects of noise as first order perturbations in the stationary frequency comb ψ o , also being valid in fourier space.
NOISE constituye un servicio del Sistema Compartido de Información Medioambiental de Europa o Shared Envi- ronmental Information System of Europe, SEIS en sus siglas en inglés, la cual es una iniciativa colaborativa de la Comisión Europea y la Agencia Europea del Medio Ambiente (AEMA) para establecer junto con los países miembros un sistema integrado de información ambiental en Europa organizado por temática medioambiental. Debido a su concepción como sistema distribuido, SEIS está construido en base a las premisas de la directiva INSPIRE, y en con- creto, en sus reglas de implementación lo que hace de SEIS, y de cada uno de sus componentes, un sistema estan- darizado e interoperable.
Considering the imminent second round of noise mapping and their subsequent 5-year periodic revision , the problem of the quality of the maps is set out . The lack of accuracy in noise mapping has a huge repercussion in Noise Action Plans , resulting in erroneous figures of people exposed to noise. Based on those wrong figures, measures to decrease noise will be taken with its related economic cost .
The rela tion betwe en long te rm LA eq and individual con tributio ns per ve hic le or m ac hine is com plicate d. Road traffic n oise is a co m pou nd o f very diffe rent a cou stical situation s: the city stree ts with re latively low am oun ts of tra ffic bu t dwe llings at s hort d istanc e an d m otorw ays w ith high traffic volumes approaching almost continuous noise but dwellings at larger distance. Aircraft noise and train noise usually have fewer events per time unit, higher sound power output, but large to intermediate distances.
In the term in the integral the sound power emitted is independent from time, as we are evaluating a machine moving at constant speed, so that W is constant. The time dependence of R (source–receiver distance) is a function of the machine’s movement and of its speed. The only term inside the integral depending on the integration variable is the source–receiver distance. This result can be obtained when the machine‘s speed is constant. Now we change the variable of integration T, having:
Primary noise is generated by a primary loudspeaker placed inside the enclosure at the furthest corner from the window, in order to excite the highest number of modes of the enclosure. The secondary source is a loudspeaker with a radius of 6 cm and the active noise control system is a typical DSP with a feedforward structure with an adaptive control using the FXLMS algorithm. The reference signal is picked up straight from the function generator to avoid potential feedback contamination.
- Traffic density is the major cause behind differences in noise levels. If we take the case of the East Way, for example, whilst traffic density during daytime reaches levels between 1600-2000 vehicles/hour (average of measurements in different sections), during the 12pm-6am period traffic density decreases to the 100-150 vehicles/hour range.
Un modelo de negocios se vincula a la producción electrónica, que el desarrollo de drivers y código de interfaz que se incluye embebido (se entrega sin costo adicional) en hardware y dispositivos que vende la empresa, como actividad principal. Podemos denominar a este modelo como de Venta de Hardware (o Widget Frosting), siguiendo a Raymond (1999a). En cierto modo, este modelo retoma el modo de producción originario del software, cuando éste se producía de un modo libre, para ser incluido como un agregado extra de las máquinas. Es difícil concebir a éste como un modelo de negocios FLOSS por fuera de otros sectores productivos, particularmente manufactureros donde existen actividades de desarrollo de software in-house para el manejo de procesos productivos, funcionamiento de maquinaria, CNC, etc. Sin embargo, puede ser relevante para empresas que combinan la actividad electrónica, la producción e software y la provisión de servicios informáticos. La introducción de software open source (sean drivers, compiladores y linkers, o incluso aplicaciones y sistemas completos), pueden ser un valor agregado que eleve las ventas del producto principal: un micro chip, una placa gráfica, un dispositivo periférico, una computadora en red, etc.).
exposure level is then measured value used for discrete events such as impulsive sound. The procedure for standard uncertainty estimation of Sound exposure level is equal to the procedure as described in item 2: “standard uncertainty estimation of equivalent continous A-weighted sound pressure level”. The rating noise level for this case is :
For that purpose, an experimental laboratory has been built in which we reproduced with realism the discomfort made by a drainpipe in the vertical free falling of the fluid in the elbow and in the horizontal route. A drainpipe has been installed over 4 floors. On the 4 th floor, a reservoir allows us to discharge the water through the drainpipe. On the 3 d floor, the drainpipe system recovers on a straight course and stripe raster which allow us to analyse the noise adherence. On the 2d floor, the drainpipe effectuates a double elbow, this configuration permits us to study the noise made by the fluids hit in the drainpipe. And finally, on the 1 st floor a reservoir is installed with a pump that allows us to keep the continuity of the system and to measure continuously with a controlled and flat debit. (See figure 1)
An attractive and instructive approach for teaching the concept of narrowband Gaussian noise (NBGN) by using MATLAB environment is presented in this article. Narrowband Gaussian process is important in communication systems [1 8], control, electronic and computer engineering , random vibrations , biomedical engineering , radar-sonar processing , under- water oceanic engineering , astronautics and aeronautics , among others.
For the functional localizer, a standard multi-slice GRE-EPI sequence with sinusoidal readout was used with the following parameters: voxel size: 2.3 mm isotropic, matrix size 96 × 96, TR/TE/flip angle = 2500/25/90°. GRAPPA = 2 and partial Fourier 6/8 undersampling were used to obtain a TE ≈ T 2 * . Forty-two near-coronal slices covering the cerebellum and centred on the motor cor- tex, including the basal ganglia and part of the occipital cortex, were acquired in each volume. fMRI data were analysed online to aid placement of subsequent higher- resolution acquisitions. For the 1-mm fMRI acquisitions, a 3D-EPI sequence [ 24 , 25 ] was used with voxel size 1.0 mm 3 isotropic, matrix size 224 × 224, TR/TE/flip angle = 2520 ms/25 ms/17°. A slab of 40 near-coronal slices covering the supplementary motor area (SMA), pri- mary sensorimotor cortex (MI/SI), secondary somatosen- sory cortex (SII) and the cerebellum was sampled every 2520 ms. GRAPPA = 3 was used to limit the length of the read-out train. The primary phase-encoding direc- tion was approximately head-foot. For all functional and rest runs, both respiratory and cardiac data were recorded using vendor-provided hardware for physiological noise modelling, with a respiratory belt and SpO2 monitor, respectively. To allow synchronization of MRI data and the recorded physiological traces, the scanner volume synchronization triggers were recorded on an analog input of the physiological monitoring unit after lengthening for reliable detection.
Plaintiffs would be happy to settle this matter with Best Buy and Phoebe Micro if they either (i) ceased all distribution of BusyBox or (ii) committed to distribute BusyBox in compliance with the free and open source license terms under which Plaintiffs offer BusyBox to the world. Plaintiffs have patiently worked with Best Buy and Phoebe Micro to bring their products into compliance with the license, but unfortunately have now concluded that those efforts are destined to fail because neither Best Buy nor Phoebe Micro has the capacity and desire to meet either of Plaintiffs' demands for settlement. As such, Plaintiffs are forced to protect their interests in BusyBox by now respectfully moving for a preliminary injunction, pursuant to Rule 65, enjoining and restraining defendants Best Buy and Phoebe Micro from any further copying, distribution, or use of their copyrighted software BusyBox.