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Frequency domain beamforming method.

Frequency domain beamforming method.

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Conference Paper
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Hybrid cars have become more important due to increasing fuel costs and the goal of reducing CO2 emissions. In this talk, the noise producing mechanisms of a Honda Civic Hybrid will be studied using a phased array and a range of beamforming techniques. The importance of multiple propagation paths, incoherent and coherent source distributions, tone...

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... only the first source is operating, with unit power, so that X= (1, 0, ..., 0) T . In this case the beamforming process would produce an array response map like the one shown in Figure 2. Let this be the first column of a matrix, A, where the second column is the beamforming result of X= (0, 1, ..., 0) T , and so on through the number of map points, N map . ...

Citations

... Nowadays, the microphone array has become the standard tool for analyzing noise sources on flying aircraft [6][7][8][9][10][11], trains [12][13][14], cars [15][16][17], snowmobiles [18], and other machinery, such as wind turbines [19,20]. Acoustic beamforming algorithms [3] are the essential link between the sound field measured at a number of microphone positions and the assessment of useful characteristics of aeroacoustic noise sources, such as their locations and absolute levels. ...
Article
Phased microphone arrays have become a well–established tool for performing aeroacoustic measurements in wind tunnels (both open–jet and closed–section), flying aircraft and engine test beds. This paper provides a review of the most well–known and state–of–the–art acoustic imaging methods and recommendations on when to use them. Several exemplary results showing the performance of most methods in aeroacoustic applications are included. This manuscript provides a general introduction to aeroacoustic measurements for non–experienced microphone array users as well as a broad overview for general aeroacoustic experts.
... Therefore, undesirable spatial leakage effects are avoided [7]. SONAH [6] and beamforming [8] techniques use a measurement system based on specially designed geometrical configurations of microphone arrays [9], which help to understand the acoustic field at a given distance from the acoustic source, using various signal processing algorithms. These techniques are mainly used to locate acoustic sources [10]. ...
... The particular process that allows building the signal group and afterwards constructing the noise level contour map which illustrates the noise source location and magnitude is called beamforming algorithms. The most recent algorithms applied in the Beamforming technique are DAMAS, DAMAS2, LORE, CLEAN-SC, and TIDY [5,6] and the adaptive method. ...
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Due to the high impact of the presence of noise in industry, it is mandatory to reduce acoustic noise hazard below the limit where risk to hearing occurs. The first step to achieve this is the identification of acoustic noise sources, which is a complex task that can be achieved using a wide range of techniques that involve different technologies for sound data acquisition, signal processing and study of physical construction. Sound source localization techniques fall into three standard categories: near-field acoustic holography, acoustic beam-forming and inverse methods. Selecting one method or another depends on the test object, nature of the sound, and the actual environment. In this paper, an intelligent system in the form of a microphone array based on a beam-forming method is proposed for noise detection and localization in porous panel structures through wind tunnel tests. The modification of an already existing experiment by the inclusion of new intelligent entities will increase the scope of these kinds of studies. Strengthening the communication level between the units involves assuring a more accurate identification of the noise sources and consequently assists in undertaking proper action to mitigate them.
... The most recent technique is the implementation of array of microphones. Among the famous methods are the beamforming method (Smith et al., 2007;Gerges et al., 2009), near-field acoustical holography (Maynard et al., 1987;Jacobsen and Jaud, 2007) and the inverse method (Nelson and Yoon, 2000;Nelson, 2001). These methods provide the measure of the 'source strength' magnitude and enable to localise the noise source accurately. ...
Article
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From various methods of measuring noise in a motor vehicle, a technique to separate the airborne and structure-borne noise is of interest as an important measure to improve the noise control treatment. This paper proposes a simple technique to measure the contribution of the airborne noise in a vehicle cabin using substitution source method. A cone loudspeaker was used as the substitution source and the airborne transfer function was measured. The technique has successfully separated the airborne transmission with the intersection frequency at roughly 400 Hz with the structure-borne noise. It is found that this is independent of the engine speed.
... Therefore, a three-dimensional mapping is desirable that allows source localisation in three dimensions. In principle, the three-dimensional application of beamforming techniques is straightforward and can be easily realised by using a three-dimensional grid [12][13][14][15][16][17][18][19][20]. However, there appear to be some practical problems in the application. ...
Article
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Acoustic source mapping techniques using acoustic sensor arrays and delay-and-sum beamforming techniques suffer from bad spatial resolution at low-aperture-based Helmholtz numbers. This is especially a problem for three-dimensional map grids, when the sensor array is not arranged around the region spanned by the grid but on only one side of it. Then, the spatial resolution of the result map in the direction pointing away from the array is much worse than in the other lateral directions. Consequently, deconvolution techniques need to be applied. Some of the most efficient deconvolution techniques rely on the properties of the spatial beamformer filters used. As these properties are governed by the steering vectors, four different steering vector formulations from the literature are examined, and their theoretical background is discussed. It is found that none of the formulations provide both the correct location and source strength. As a practical example the CLEAN-SC deconvolution methodology is applied to simulated data for a three-source scenario. It is shown that the different steering vector formulations are not equally well suited for three-dimensional application. The two preferred formulations enable the correct estimation of the source location at the cost of a negligible error in the estimated source strength.
... More detailed information about the system and the geometry performance can be found in [9]. ...
Conference Paper
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Beamforming techniques use microphone arrays to detect prominent sound sources, also providing the direction of arrival (DOA) of each given sound source. Usually, source maps are then analyzed to find an acoustic optimization of a product, mostly by reducing the influence of the main sources in terms of sound pressure levels. A common tool for the subjective evaluation of products in terms of sound quality is the binaural recording with a dummy head. This work aims to combine these two approaches by using data from microphone array measurements to simulate binaural signals that would be acquired by an artificial head at the position of the array. The auralization and therefore simulation of the dummy head is obtained by spatial filtering of known sound sources with directionally dependent filters from a head related transfer functions (HRTF) database. The positions of the different sound sources are obtained by source localization methods. Since the position of the object can be roughly estimated, unwanted noise sources from different directions can be suppressed by this method. By considering moving sources, the common techniques of linear-time invariant systems are not applicable anymore. The DOA has to be repeatedly estimated and the spatial filtering adapted accordingly. This paper proposes two different approaches for the offline auralization of beamforming measurements. The results are discussed regarding audible artifacts due to the movement of the sources and the 3D impression of the auralized events.
... Other advanced techniques can be found in [5,6,7]. ...
Conference Paper
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Beamforming is an acoustic imaging technique that can estimate the radiation pattern of simple or complex sound sources and produce a map of the results. The pass-by noise test is a standardized test that aims to evaluate the overall noise of vehicle’s sideline. By coupling the idea of pass-by test with the extension of beamforming technique to moving sources provides the access to the recognition of sound sources produced by vehicle movements, for example, rolling tires, engines and exhaust systems. The present paper aims to describe a low cost system to apply the beamforming technique to pass-by noise test. The system is based on the use of low cost electret microphones mounted in a metallic array which are connected by a coaxial cable to the acquisition system. Later in this document in the application section the results of beamforming maps of pass-by noise test can be viewed in more detail.
... where p m is the sound pressure associated to each microphone, b(t) is the response in the time domain of beamforming, w m is the weighting and ∆ m the delay for the m th microphone. If the time history is not necessary for the experiment, the algorithm in the frequency domain can offer some advantages over the time domain, such as reduction of side lobes, techniques for removal of spurious noise, among others [20,21]. The acoustic images of this experiment were obtained by post processing with advanced beamforming algorithms: DAMAS2 and TIDY. ...
Conference Paper
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Viscoelastic material is commonly used in the passive treatment of structural vibration of the vehicle structure, to introduce damping and reduce vibration level at resonance frequencies. In a passenger vehicle chassis it is usual to add around 10 kg of these viscoelasctic patches. The effectiveness of such damping treatment depends on design parameters such as application location, area, thickness, and choice of the type of damping material. This paper describes an experimental procedure implemented to evaluate the performance of two different layers of damping material, when they are applied to a passenger vehicle chassis (white body). Results are presented for the white body chassis: 1) without damping added, 2) with asphalt pad added and 3) with liquid applied sprayable damper. The results are discussed through a comparison with adequated mapping of the responses and by results from beamforming tests in a chassis prototype, in terms of its efficiency for the damping of vibrations.
... There are improved algorithms that can supress part of the limitations of this classical beamforming. In this work, almost of all the post-processing was performed with enhanced techniques, such as TIDY and DAMAS2, as discussed in Gerges et al. , 2009. Further information about the acquisition system, array reponse and other principles of beamforming can be found in Fonseca, 2009. ...
Conference Paper
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Damping materials such as Asphalt Melt Sheet and LASD material (Liquid Applied Sprayable Damper) are used to reduce vibration levels within passenger vehicles. The performance of the acoustic package depends on the position of application and the thickness of the material. These parameters must be optimized to ensure the best performance with lower cost and weight. However, the effect of this positioning on sound radiation has not been evaluated. This article presents a study ofsound radiation behavior in an ideal prototype passenger vehicle with optimized damping treatmentusing beamforming techniques. Beamforming was applied before and after application of damping material. This aims to elucidate the regions of higher sound radiation and the noise reduction after damping treatment.
Conference Paper
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In general maximum noise emission levels are given by global regulations values. Noise regu-lations are becoming more demanding due to the harmful effect in the population and the en-vironment. Therefore there is a need to determine which source components contribute to the overall noise. The technique used in this work is the creation of acoustic images by employing the beamforming procedure. The acoustic images are constructed using an antenna located at relative distance from the noise source. The acoustic antenna consists of a spatial arrangement of pressure sensors. The pressure sensor distribution is investigated by an optimization proce-dure. The pressure sensor spatial distribution affects the antenna dynamic range. In particular the dynamic range is strongly influenced by the Maximum Side Lobe (MSL). The dynamic range parameter was optimized by the usage of genetic algorithms. The acoustic imaging technique is used in this endeavour with various pressure sensors distributions in order to show the MSL effect. The development of the acoustic image system permits to localize in space, time and frequency the different source contribution to the global noise radiation. Once that the main sources are distinguished different approaches can be used to control or minimize the source emission to the environment.