330 research outputs found

    Three-dimensional point-cloud room model in room acoustics simulations

    Get PDF

    Fourier based high-resolution near-field sound imaging

    Get PDF
    Noise pollution is a generally acknowledged problem in modern day society. The current tendencies towards lightweight and cheaper product design are primarily responsible for increasing nuisance, annoyance and environmental problems caused by acoustic noise. There are several reasons for research towards technologies that facilitate acoustic noise reduction. Nowadays, low noise design of consumer electronics, high-tech systems and automotive are restricted to increasingly stringent regulations and quality aspects. Effective countermeasures in order to reduce sound radiation are only taken when the source of sound is known. "Inverse Acoustics" is a very effective method to visualize and quantize the sound sources, which reconstructs source information based on measurements away from the source, yet in the near-field. In fact, the system is able to reconstruct the entire acoustic message that a source radiates in the direction of interest. The current methods for source reconstruction produce sound images with very little detail, they often require cumbersome numerical calculations and models, and they are often highly impractical for industrial applications. This research focuses on fast and accurate measurement and signal processing methods for inverse acoustics that are applicable in practical situations which require high resolutions under hazardous acoustic conditions. The inverse process is based upon spatial and wavenumber domain Fourier techniques, also referred to as Near-field Acoustic Holography. More in detail, spatial properties with respect to aliasing, leakage, signal-to-noise ratio and sensor set-ups are investigated and explicit methods and rules are developed to assist in proper determination of the acoustic holograms. In order to correctly transform the spatial hologram data into the wavenumber domain or k-space, a method called border-padding is developed. This method, which is an alternative to spatial windowing, is highly accurate without slowing down the processing time considerably. Another important factor is regularization, which is required since the inverse process is highly ill-posed. Without proper filtering action taken, noise blows up as the hologram-source distance or the wavenumber grows. In this research project a method is developed to automatically determine the proper filter function and filter parameters, which is a near-optimal trade-off between noise blow-up and deterioration of useful source information. These important properties are combined in a fully automated near-field sound imaging system design. At the Technical University of Eindhoven two versions of this system were developed and built; a large version that is based in the semi-anechoic room of the laboratory and a portable system that is suitable for small electronic devices and high-tech systems. A number of practical cases are used to qualitatively as well as quantitatively validate the improvements with respect to existing methods and illustrate the possibilities for industrial application

    Proceedings of the 10th International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components

    Get PDF
    This conference, the tenth in a series on NDE in relation to structural integrity for nuclear and pressurized components, was held from 1st October to 3 October 2013, in Cannes, France. The scientific programme was co-produced by the European Commission’s Joint Research Centre, Institute for Energy and Transport (EC-JRC/IET). The Conference has been coordinated by the Confédération Française pour les Essais Non Destructifs (COFREND). The first conference, under the sole responsibility of EC-JRC was held in Amsterdam, 20-22 October 1998. The second conference was locally organized by the EPRI NDE Center in New Orleans, 24-26 May 2000, the third one by Tecnatom in Seville, 14-16 November 2001, the fourth one by the British Institute of Non-Destructive Testing in London, 6-8 December 2004, the fifth by EPRI in San Diego, 10-12 May 2006, the sixth by Marovisz in Budapest, 8-10 October 2007, the seventh by the University of Tokyo and JAPEIC in Yokohama, the eight by DGZfP, 29 September to 1st October 2010, the ninth by Epri NDE Center, 22-24 May 2012 in Seattle. The theme of this conference series is to provide the link between the information originated by NDE and the use made of this information in assessing structural integrity. In this context, there is often a need to determine NDE performance against structural integrity requirements through a process of qualification or performance demonstration. There is also a need to develop NDE to address shortcomings revealed by such performance demonstration or otherwise. Finally, the links between NDE and structural integrity require strengthening in many areas so that NDE is focussed on the components at greatest risk and provides the precise information required for assessment of integrity. These were the issues addressed by the papers selected for the conference.JRC.F.5-Nuclear Reactor Safety Assessmen

    Ultrasound cleaning of microfilters

    Get PDF

    Temporal integration of loudness as a function of level

    Get PDF
    • …
    corecore