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A Bridging Technology to Combine Test and Simulation With In-Situ TPA

Head acoustics GmbH-Matthias Wegerhoff, Roland Sottek, Haiko Brücher
  • Technical Paper
  • 2020-01-1574
To be published on 2020-06-03 by SAE International in United States
To shorten development processes and to secure decisive product properties as early as possible, new methods are required for product development. These must be able to generate the maximum information about the future product out of the data available at the respective development step. Computer-aided engineering (CAE) is therefore becoming increasingly important. CAE makes it possible to predict product properties at an early development stage and to partly replace physical prototypes with numerical models (virtual prototypes). However, the transition from experiment-based methods to numerical approaches is a big step. Often, purely-numerical examinations are only possible to a limited extent because of the following reasons: complex modeling, missing data or input data with major uncertainties, lack of expertise, or development processes not suitable for numerical methods. Therefore, this paper addresses a "bridging technology" that combines the advantages of experiment-based and numerical methods and allows optimal evaluation of the properties of the product to be developed. For this purpose, an exciting subsystem with its structural dynamics is represented by Equivalent Forces (EF) determined based on measured accelerations…
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Psychoacoustic Order Tonality Calculation

SAE International Journal of Advances and Current Practices in Mobility

HEAD acoustics GmbH-Julian Becker, Roland Sottek
  • Journal Article
  • 2019-01-1466
Published 2019-06-05 by SAE International in United States
Quantifying tonalities in technical sounds according to human perception is a task of growing importance. The psychoacoustic tonality method, published in the 15th edition of the ECMA-74 standard, is a new method that is capable of calculating the perceived tonality of a signal. Other methods, such as Prominence Ratio or Tone-to-Noise Ratio do not consider several essential psychoacoustic effects. The psychoacoustic tonality is based on a model of human hearing and thus is able to model human perception better than other methods. The algorithm described in ECMA-74 calculates tonality over time and frequency. In practice, tonalities often originate from rotating components, for example, parts of an electric motor. In these cases, quantification of the tonality of orders is often more interesting than the tonality over frequency. In this paper, an extension of the psychoacoustic tonality according to ECMA-74 is presented. With this extension, it is possible to calculate the order tonalities by using the rotational speed characteristics of the measured signal in order to control the parameters of the auditory filter bank. Two of the…
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Application of a New Perceptually-Accurate Tonality Assessment Method

SAE International Journal of Passenger Cars - Electronic and Electrical Systems

HEAD acoustics GmbH-Roland Sottek
HEAD acoustics Inc-Wade Bray
  • Journal Article
  • 2015-01-2282
Published 2015-06-15 by SAE International in United States
For many years in vehicle and other product noise assessments, tonality measurement procedures such as the Tone-to-Noise Ratio, Prominence Ratio and DIN 45681 Tonality have been available to quantify the audibility of prominent tones. Especially through the recent past as product sound pressure levels have become lower, disagreements between perceptions and measurements have increased across a wide range of product categories including automotive, Information Technology and residential products. One factor is that tonality perceptions are caused by spectrally-elevated noise bands of various widths and slopes as well as by pure tones, and usually escape measure in extant tools. Near-superpositions of discrete tones and elevated narrow noise bands are increasingly found in low-level technical sounds. Existing pure-tone methodologies tend to misrecognize an elevated noise band as general masking lowering the audibility of a tone in the measured vicinity, whereas perceptually they add. To address such issues a new psychoacoustically-based tonality model is presented which evaluates the nonlinear and time-dependent loudness of both tonal and broadband components, separating them via the autocorrelation function (ACF) and giving their…
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Parameterizing Mount Models from In-Situ Measurements

Head acoustics GmbH-Bernd Philippen, Roland Sottek
Published 2015-06-15 by SAE International in United States
Transfer Path Analysis and Synthesis is a widely-used troubleshooting and engineering method in the development process of a car. An engine TPA model should include the engine mounts because they are important elements of the structure-borne paths from the engine to the driver's ears. This allows identifying if the structure, the sound radiation or the mount is a weak point of the transmission. A mount can be characterized, e. g., by a mount attenuation function, a four-pole model, or a simple parametric mount model. If the mount characteristics are known, the influence of a different mount on the structure-borne sound can be virtually predicted without a real modification.The mount characteristics could be determined on special test rigs but the transferability to the real situation is often questionable because the same boundary conditions on the test rig and in the car are difficult to guarantee. On the other hand, special test rigs must be adapted for each mount: this requires time and money. Time is strictly limited due to shorter development cycles. Thus, a TPA method…
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Synchronization of Source Signals for Transfer Path Analysis and Synthesis

HEAD acoustics GmbH-Roland Sottek, Bernd Philippen
Published 2014-06-30 by SAE International in United States
In the engine development process, the ability to judge NVH comfort as early as possible is a great benefit. The prediction of engine noise on the basis of a prototype engine without the need to install it in a real car significantly speeds up the development process and leads to a cost reduction, as prototype modifications can be evaluated faster.Meaningful predictions of the perceived NVH comfort cannot be achieved just by comparing order levels, but require listening to an auralization of the engine noise at the driver's position. With the methods of Transfer Path Analysis and Synthesis (TPA/TPS) a prototype engine can be virtually installed in a car using test-bench data. The interior noise can be estimated by combining source signals containing near-field airborne noise radiation and mount forces with transfer functions describing the transmission to the target position in the cabin. Even the transfer functions of a predecessor car could be used if the new car body is not yet available.For several reasons, the source signals for TPA/TPS cannot always be measured simultaneously, in…
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An Unusual Way to Improve TPA for Strongly-Coupled Systems

SAE International Journal of Passenger Cars - Mechanical Systems

HEAD acoustics GmbH-Roland Sottek, Bernd Philippen
  • Journal Article
  • 2013-01-1970
Published 2013-05-13 by SAE International in United States
In a vehicle's development process, Transfer Path Analysis (TPA) is commonly used for identifying sound sources and their transmission to a receiver. Forces acting on the structure are the reason for the structure-borne sound share of the vehicle interior noise. In practice it is not possible, or too extensive, to measure operational forces directly. Instead, they are often calculated indirectly from accelerations and from additionally measured inertances. As the car body is a strongly coupled system, a force acting at one position results in accelerations throughout the structure. This crosstalk must be considered by using a dense inertance matrix consisting of the ratios between each force excitation and the accelerations at every sensor position. Then a matrix inversion is performed to solve the system of equations describing the coupling of the structure. For an engine TPA, this method has the disadvantage that it does not include the mounts, although their characteristics can have a major impact on the interior noise.Another widely-used method predicts each body acceleration from the corresponding acceleration at the engine using the…
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Advanced Methods for the Auralization of Vehicle Interior Tire-Road Noise

HEAD acoustics GmbH-Roland Sottek, Bernd Philippen
Published 2012-11-25 by SAE International in United States
Besides powertrain and aerodynamic noise, tire-road noise is an important aspect of the acoustic comfort inside a vehicle. For the subjective evaluation of different tires or vehicles in a benchmark, authentic sound examples are essential. They should be recorded on a real road rather than on a roller dynamometer (avoiding artificial and periodic sounds, especially in the case of a small roller circumference and a smooth surface). The challenge of on-road measurements is the need for separating the components of the interior noise generated by rolling tires, aerodynamic flow and powertrain. This allows for individual judgment of the noise shares.A common approach for eliminating the engine sound is shutting the engine off after acceleration to the desired maximum speed. Operational Transfer Path Analysis (OTPA) can then be used to auralize the tire-road noise at a certain receiver location, where an artificial head records the interior noise during this coast-down. Further signals are needed which are measured with a triaxial accelerometer at each wheel carrier and microphones applied near the tires. Because the aerodynamic flow is…
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Tire-Road Noise Analysis of On-Road Measurements under Dynamic Driving Conditions

SAE International Journal of Passenger Cars - Mechanical Systems

HEAD acoustics GmbH-Roland Sottek, Bernd Philippen
  • Journal Article
  • 2012-01-1550
Published 2012-06-13 by SAE International in United States
The powertrain noise of cars has been reduced in the last decades. Therefore in many cases, rolling tires have increasingly become the dominant sources of vehicles' interior noise. For sound design or a reduction of tire-road noise it is important to know the individual noise shares of the tires and their transfer paths. Authentic tire-road noise can only be measured on a real road, not on a roller dynamometer. So far measurements have been performed during a coast-down on the road with the engine switched off, avoiding the influence of engine noise.Operational Transfer Path Analysis (OTPA) can be used to remove the uncorrelated wind noise, and to synthesize structure-borne and airborne tire-road noise based on input signals measured with microphones at the tires and a triaxial accelerometer at each wheel carrier. Simultaneously, the interior noise is recorded by an artificial head.Acceleration, deceleration or other driving maneuvers with the engine running can lead to different tire noises. In this case the conventional method cannot be applied because the engine sound is measured at the source (tires)…
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Advanced Source Localization Techniques Using Microphone Arrays

SAE International Journal of Passenger Cars - Mechanical Systems

Head acoustics GmbH-Sandro Guidati, Roland Sottek
  • Journal Article
  • 2011-01-1657
Published 2011-05-17 by SAE International in United States
Microphone arrays used in vehicle acoustics are mainly designed for fast setup and basic evaluation (e.g. using delay-and-sum beamforming) resulting in a restriction to free field environments. Applications in vehicle interiors require advanced source localization techniques taking into account the reflections at the different panels appearing as mirror sources.Coherence filtering techniques allow for the detection of these mirror sources. An additional sensor is placed as a reference close to the main source. This reference signal is used to filter the array signals increasing the overall dynamic range of the acoustic source mapping. The discrimination of the original source and the reflections is obtained by manipulating the impulse responses between the reference signal and all microphone signals.Other advanced signal processing techniques can be used to increase the limited dynamic range of conventional beamforming such as principal component analysis removing the dominant sources. An implementation allowing for online application based on spatial filters will be presented.In addition the production requirements of large scale arrays, for example wind tunnel measurements and pass-by or fly-over measurements, are discussed. Manufacturing…
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Reciprocal Measurements of Transfer Functions for Auralization

Head acoustics GmbH-Roland Sottek
Published 2011-05-17 by SAE International in United States
Many applications in acoustics, such as transfer path analysis and synthesis (the well-known tools for troubleshooting and sound design of vehicle interior or exterior noise), require the measurement of transfer functions.Several methods are available to determine the transfer functions between identified sources and selected receiver locations. For example, transfer functions can be obtained by means of direct or reciprocal measurements. Due to errors and restrictive constraints during the measurements, the results of the two methods differ.The quality of measured transfer functions must be evaluated with respect to the auralization of the synthesized receiver signals or even the auralization of individual noise shares caused by a specific source and transmitted via one or a combination of paths.This paper compares the different measurement techniques of transfer functions in theory and in practice. Application examples (simple mechanical structure and vehicle) are presented on the one hand to illustrate the advantages of reciprocal measurements, and on the other hand to sensitize for potential drawbacks caused by the different sources of errors.
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