Guillermo de Arcas

A new 3D finite element model of the IEC 60318-1 artificial ear

The artificial ear specified in IEC 60318-1 is used for the measurement of headphones and has been designed to present an acoustic load equivalent to that of normal human ears. In this respect it is specified in terms of an acoustical impedance, and modelled by a lumped parameter approach. However, this has some inherent frequency limitations and becomes less valid as the acoustic wavelength approaches the characteristic dimensions within the device. In addition, when sound propagates through structures such as narrow tubes, annular slits or over sharp corners, noticeable thermal and viscous effects take place causing further departure from the lumped parameter model. A new numerical model has therefore been developed, which gives proper consideration to the aforementioned effects. Both kinds of losses can be simulated by means of the LMS Virtual Lab acoustic software which facilitates finite and boundary element modelling of the whole artificial ear. A full 3D model of the artificial ear has therefore been developed based on key dimensional data found in IEC 60318-1. The model has been used to calculate the acoustical impedance, and the results compared with the corresponding data determined from the lumped parameter model. The numerical simulation of the artificial ear has been shown to provide realistic results, and is a powerful tool for developing a detailed understanding of the device. It is also proving valuable in the revision of IEC 60318-1 that is currently in progress.

Image acquisition and GPU processing application using IRIO technology and FlexRIO devices

The large amount of data generated by image diagnostics used in big physics experiments requires an efficient use of hardware technologies in real time data acquisition and processing applications. In order to get the best performance of the hardware, it is necessary to provide the hardware and software tools that enable a fast and easy way to deployment these kind of solutions. IRIO technology allows an easy development of advanced data acquisition applications and their integration in EPICS using National Instruments Reconfigurable Input/Output (RIO) FPGA-based cards. Using IRIO software tools, it is possible to minimize the development time to build specific application for different hardware configurations. IRIO uses the open source version of NI-RIO Linux device driver supporting direct DMA access from FlexRIO devices to NVIDIA GPUs. For the development of image processing applications the hardware platform selected has been implemented using a FlexRIO device with a cameralink adapter module and a NVIDIA Kepler architecture GPU. With the help of IRIO tools the user have to focus the development exclusively in the implementation of the FPGA application for the FlexRIO device using LabVIEW/FPGA and the GPU algorithm using NVIDIA CUDA tools. Additionally IRIO provides the EPICS integration for these applications using the software model developed by ITER and Cosylab that simplifies the development of EPICS device support by mean of Nominal Device Support approach. This is a set of libraries with C++ classes simplifying the development of these device supports. To demonstrate the full development cycle an algorithm for image compression based on JPEG standard has been evaluated and tested using a hardware configuration with the same elements defined in the ITER fast controllers hardware catalog. This image standard allows high compression ratios and can include additional metadata information related to the image. These software tools has been tested in ITER CCS (Codac Core System).

A new 3D finite element model of the IEC 60318-1 artificial ear: II. Experimental and numerical validation

In part I, the feasibility of using three-dimensional (3D) finite elements (FEs) to model the acoustic behaviour of the IEC 60318-1 artificial ear was studied and the numerical approach compared with classical lumped elements modelling. It was shown that by using a more complex acoustic model that took account of thermo-viscous effects, geometric shapes and dimensions, it was possible to develop a realistic model. This model then had clear advantages in comparison with the models based on equivalent circuits using lumped parameters. In fact results from FE modelling produce a better understanding about the physical phenomena produced inside ear simulator couplers, facilitating spatial and temporal visualization of the sound fields produced.The objective of this study (part II) is to extend the investigation by validating the numerical calculations against measurements on an ear simulator conforming to IEC 60318-1. For this purpose, an appropriate commercially available device is taken and a complete 3D FE model developed for it. The numerical model is based on key dimensional data obtained with a non-destructive x-ray inspection technique. Measurements of the acoustic transfer impedance have been carried out on the same device at a national measurement institute using the method embodied in IEC 60318-1. Having accounted for the actual device dimensions, the thermo-viscous effects inside narrow slots and holes and environmental conditions, the results of the numerical modelling were found to be in good agreement with the measured values.

Communicating airport noise emission data to the general public

Despite the efforts that the aviation industry has undertaken during the last few decades, noise annoyance remains high, partly because of the continuous transport demands of modern societies and partly because of changes in citizen expectations and their growing environmental concerns. Although modern aircraft are considerably quieter than their predecessors, the number of complaints has not decreased as much as expected. Therefore, the aeronautical sector has tried more sociological and/or psychological strategies to gain acceptance through awareness and community engagement. In this regard, noise communication to the public is crucial for managers and policy makers. Noise information is a difficult technical topic for non-experts, which is an issue that must first be addressed to take advantage of the new possibilities that have recently been opened by the internet and information and communication technologies. In this review paper, we have compiled the literature that shows the increasing importance of communicating noise information from aircraft and the variety of indicators used to communicate with the public. We also examined the methods of representing noise data, using visualization strategies, and new tools airports are currently using to address this communication problem.

Personal computer and frequency analyzer measure reverberation time

This paper shows how a frequency analyzer (such as Bruel and Kjaer’s Model 2144) can be used to perform reverberation time measurements with the help of some extra software. Although a particular solution is presented, the concept can be applied to any frequency analyzer that has a programmable interface. Bruel and Kjaer’s Model 2144 is a powerful frequency analyzer, but it does not measure reverberation time. On the other hand, the analyzer has a programmable interface (GPIB) that permits us to control the instrument from a personal computer. This paper shows how a software application has been developed that gives the B&K2144 connected to a computer, the capacity of measuring reverberation time. The application has been developed using LabVIEW and it makes reverberation time measurements easy and reproducible.

Machine vision improves sound level meter calibration

In this paper, important improvements in sound level meter (SLM) calibration are presented. One of the most important problems that the calibration laboratories are facing today is the long time required for calibrating certain SLMs. Instruments without a dc output require that an operator reads the SLM response in every test. This makes the process slow and tedious, and induces errors due to the operators fatigue. By using an image acquisition card with a low cost analog camera to acquire an image of the sound level meters display, calibration time can be reduced significantly. Once an image of the SLMs display has been acquired, machine vision techniques (OCR) are used to recognize the sound level meter indication. This process reduces calibration time and errors produced by operators fatigue.

Uniform error distribution in one‐third octave band frequency analysis

In this paper an algorithm for obtaining a uniform error distribution in one‐third octave band frequency analysis is presented. The algorithm is a digital signal processing implementation of the ANSI S1.11‐1986 standard based on digital filters. First the effects of constant integration time over error distribution are discussed and then a solution is presented based on a statistical signal processing interpretation of the problem. The power distribution measurement is analyzed and studied as a variance estimation problem to establish the requirements of the analysis algorithm that will guarantee a uniform error distribution. The object of the algorithm is to obtain a uniform error distribution maintaining the total number of operations as low as possible in order to be efficient enough to be implemented in real time. The discussion is completed with several simulation results and a performance comparison with other popular alternatives.

A low‐cost sound level meter based on personal computer

In this abstract a low‐cost sound level meter is developed with the help of digital signal processing techniques and an integrated programming environment. The instrument is based on the use of a general purpose data acquisition PC card to acquire the signal and a powerful digital signal processing algorithm based on digital filters to compute a one‐third octave band analysis conforming to ANSI S1.11‐1986 in real time. The objective is made possible thanks to the use of optimized signal processing routines from Intel Signal Processing Library. The use of this library and an instrumentation specific integrated programming environment such as LabWindows/CVI (National Instruments) makes it possible to design a low‐cost instrument in a very short time. The algorithm is a multirate filter bank implementation of the standard. The discussion is completed with several simulations and benchmarks are presented for different design situations. Execution time is also compared to that obtained with a popular digital s...