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Noise Source Identification with Increased Spatial Resolution Used in Automotive Industry

Bruel & Kjar Sound & Vibration Measurements A/S-Svend Gade, Jorgen Hald
Bruel & Kjar Sound & Vibration Measurements A/s-Bernard Ginn
  • Technical Paper
  • 2012-08-0099
Published 2012-05-23 by Society of Automotive Engineers of Japan in Japan
Delay-and-sum (DAS) Planar Beamforming has been a widely used Noise Source Identification Technique for the last decade. It is a quick one shot measurement technique being able to map sources that are larger than the array itself. The spatial resolution is proportional to distance between array and source, and inversely proportional to wavelength, thus the resolution is only good at medium to high frequencies. Improved algorithms using iterative de-convolution techniques offers up to ten times better resolution. The principle behind these techniques is described in this paper, as well as measurement examples from the automotive industry are presented.
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Multi-Field Microphone~a New Tool for More Reliable High Frequency Sound Measurements Inside Vehicles

Bruel & Kjaer Japan-Toshikazu Satoh
Bruel & Kjaer Sound & Vibration Measurements A/S-Svend Gade, Niels V. Boegholm
  • Technical Paper
  • 2011-08-0306
Published 2011-10-12 by Society of Automotive Engineers of Japan in Japan
Only a small percentage of all acoustical measurements are performed in the well-defined and well-controlled environment of a calibration laboratory - most acoustical measurements are done under non-controlled acoustical conditions such as inside a vehicle cabin. The major source of error is often neglected: The response of the actual microphone type in the actual sound field. The worst-case measurement error may exceed 10 dB @ 20 kHz using a high quality standard 1/2 inch measuring microphone. A multi-field microphone reduces the measurement error dramatically but at the same time fulfilling requirements in the IEC 61672 series (the "Sound Level Meter standard").
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LAN-XI, a Distributed Front-End Concept for NVH Measurements

Brüel & Kjaer-Svend Gade, Niels-Jørgen Jacobsen, Ole Thorhauge
  • Technical Paper
  • 2009-08-0033
Published 2009-05-20 by Society of Automotive Engineers of Japan in Japan
LAN-XI front-end modules can work stand alone as field portable systems, as distributed systems or in a classic frame/rack-based setup. The modules use one LAN cable for data transfer, power and synchronization. This is the benefit of new technologies such as Power over Ethernet (IEEE 802.3 af) and PTP (Precision Time Protocol - IEEE 1588) as well as each module has very robust magnesium casing. This gives a new measurement situation, where you can move the front-end modules closer to the measurement object using cheap LAN cables and use fewer/shorter transducer cables yielding better measurement quality.
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Efficient Interior Noise Source Identification Based on Conformal Mapping Using SONAH Holography for Details on Selected Panels

Brüel & Kjaer-Jørgen Hald, Jakob Mørkholt, Jesper Gomes, Svend Gade
  • Technical Paper
  • 2008-08-0127
Published 2008-05-21 by Society of Automotive Engineers of Japan in Japan
The present paper describes a set of a array-based methods that can provide both a snapshot overview of problematic areas across the panels of a car cabin and perform efficient analysis of details of a noise problem. The snapshot overview is obtained with Beamforming, while detailed analysis of problematic areas is performed with a small planar single-layer or double-layer array in combination with SONAH holography. Using the SONAH algorithm for patch near-field acoustic holography, all sound field parameters can be estimated directly on the irregularly shaped panel surfaces. All the array measurements can be performed very efficiently by the use of a position measurement system integrated with the array. Panel geometry can also be measured using the position measurement system. The paper gives an overview of the different methods and presents results from a case study.
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Transducer Response Equalization

Brüel & Kjaer-Svend Gade, Ole Thorhauge, Tommy Schack
  • Technical Paper
  • 2008-08-0216
Published 2008-05-21 by Society of Automotive Engineers of Japan in Japan
This paper describes a new technique, Response Equalization Extreme (REq-X) that enhances the frequency range and accuracy of transducers. This technique, which is implemented in PULSE, the Brüel & Kjaer Multi Analysis System Type 3560, allows you to equalize for the frequency response of transducers in real time. This significantly extends the usable frequency range of transducers. The REq-X technique corrects the time signal of a transducer by the inverse of its calibrated frequency response, and can be added to any device with a frequency response stored in the PULSE Transducer database, e.g., Brüel & Kjaer microphones and accelerometers. Brüel & Kjaer TEDS transducers are automatically detected. This means, for example, that you can use the same microphone in any kind of sound field. Furthermore the microphone can be corrected for angle of incidence and for various accessories.
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Autotracking: Examples of Order Tracking Measurements Without Using a Tacho Probe

Brüel & Kjaer Sound and Vibration Measurement A/S-Svend Gade, Thorkild Find Pedersen, Henrik Herlufsen, Hans Konstantin-Hansen
  • Technical Paper
  • 2007-08-0031
Published 2007-05-23 by Society of Automotive Engineers of Japan in Japan
When analyzing the behavior of rotating or reciprocating machines, it is often necessary to estimate and track the phases and magnitudes of harmonic orders of the fundamental frequency of the machine. The fundamental frequency is typically measured using dedicated sensors, e.g., proximity probes of photo-sensors that require direct access to the rotation parts of the machine, which can be difficult. In this paper the autotracking method where the fundamental frequency is extracted from the measured vibration/or acoustic signals is described. Hereby the need for a dedicated tacho probe is avoided. The method is founded by Bayesian statistics, where the posterior distribution of the fundamental frequency is computed conditioned on the measured data and a harmonic model of the signal. Limited prior knowledge is required for initialization. A number of application examples are included in the paper: Vibration signal from a Drivetrain and Turbocharger, sound signal from a HATS placed inside a DaimlerChrylser SmartCar and finally sound & vibrations signal from the engine compartment of a Volvo S60.
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Eliminating the Influence of Harmonic Components in Operational Modal Analysis

Brüel & Kjaer-Niels-Jørgen Jacobsen, Svend Gade
Structural Vibration Solutions-Palle Andersen, Rune Brincker
  • Technical Paper
  • 2007-08-0034
Published 2007-05-23 by Society of Automotive Engineers of Japan in Japan
Operational modal analysis is used for determining the modal parameters of structures for which the input forces cannot be measured. However, the algorithms used assume that the input forces are stochastic in nature. While this is often the case for civil engineering structures, then mechanical structures, in contrast, are subject inherently to deterministic forces due to the rotating parts in the machinery. These forces are seen as harmonic components in the responses, and their influence should be eliminated before extracting the modes in their vicinity.This paper describes a new method based on the well-known Enhanced Frequency Domain Decomposition (EFDD) technique for eliminating these harmonic components in the modal parameter extraction process. For assessing the quality of the method, various experiments were carried out where the results were compared with those obtained with pure stochastic excitation of the same structure. Good agreement was found and the method is shown to be an easy and robust tool for enhancing the EFDD technique for mechanical structures.
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Preparation and Validation of Data for Use in an Interactive NVH Simulator

Bruel & Kjaer-Bernard Ginn, Svend Gade
Sound Evaluations Ltd.-Roger Williams
  • Technical Paper
  • 2007-08-0304
Published 2007-05-23 by Society of Automotive Engineers of Japan in Japan
To achieve high levels of accuracy required for the driver-in-loop sound synthesis performed by the NVH Simulator, it is necessary to have good quality data covering the full audible frequency range for all the driving conditions which will be included in the simulation. This paper recommends a workflow to maximize the efficiency of the entire process in which the data collection and data preparation tasks have been optimized, in parallel with the development the real-time sound synthesis methods used in the simulator.
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Practically Obtainable Dynamic Ranges of Data Acquisition Systems Based on 24-Bit Technology

Brüel & Kjaer Sound and Vibration Measurement A/S-Svend Gade, Ole Thorhauge Andersen, Niels Jørgen Jacobsen
  • Technical Paper
  • 2006-08-0389
Published 2006-05-01 by Society of Automotive Engineers of Japan in Japan
The linear operating range of high-quality measurement accelerometers and microphones has for many years been significantly better than that which can be achieved in the analog signal conditioning electronics and analog-to-digital converters (ADCs) of data acquisition systems. This is despite the fact that data acquisition systems today are typically based on 24-bit ADCs, thereby theoretically being able to handle signal dynamics of up to 146 dB. In practice however, most of these systems do not have a useful dynamic range higher than 100 - 110 dB. Consequently, the system operators must for a number of applications be very careful in optimizing the signal chain dynamics in order to avoid overload and underrange situations. This paper describes the high dynamic ranges that can be achieved in practice using today's state-of-the-art designs.
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The Use of Order Tracking in Vibro-Acoustic Measurements: A Novel Approach Eliminating the Tacho Probe

Brüel & Kjaer Sound Vibration Measurement A/S-Svend Gade, Thorkild Find Pedersen, Henrik Herlufsen, Hans Konstantin-Hansen
  • Technical Paper
  • 2006-08-0001
Published 2006-05-01 by Society of Automotive Engineers of Japan in Japan
When analyzing the behavior of rotating or reciprocating machines, it is often necessary to estimate and track the phases and magnitudes of harmonic orders of the fundamental frequency of the machine. The fundamental frequency is typically measured using dedicated sensors, e.g., proximity probes or photo-sensors that require direct access to the rotating parts of the machine, which can be difficult. In this paper we propose a new order tracking method where the fundamental frequency is extracted from the measured vibration and/or acoustic signals. Hereby the need for a dedicated tacho probe is avoided. Apart from the fundamental frequency, the method can also estimate the amplitude and phase of specified orders. The method is founded on Bayesian statistics, where the posterior distribution of the fundamental frequency is computed conditioned on the measured data and a harmonic model of the signal. Limited prior knowledge is required for initialization. The new method is tested on vibration signals from the drivetrain of a passenger car and is compared with two other order tracking methods: re-sampling based order tracking and…