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Philippen, Bernd
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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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Separation of Airborne and Structure-Borne Tire-Road Noise Based on Vehicle Interior Noise Measurements

HEAD acoustics GmbH-Roland Sottek, Bernd Philippen
Published 2010-06-09 by SAE International in United States
Vehicle interior noise consists of a superposition of broadband contributions from powertrain, wind, and tire-road noise. Tire-road noise has become increasingly important referring to overall acoustic comfort, especially for (luxury) sedans with pleasant low-noise engine sounds. An interior noise recording during a coast-down (engine switched off) contains different components: a mixture of wind along with airborne and structure-borne tire-road noise shares. Separating the mixture into these components requires appropriate algorithms and additional measurements. Therefore, structure-borne excitation signals as well as the airborne noise radiation of all four tires are measured simultaneously to an artificial head recording in the vehicle interior during a coast-down test from maximum vehicle speed to standstill. Based on the fact that wind and tire-road noise are uncorrelated, evaluating the multiple coherence between the excitation signals and the simultaneous binaural recording allows calculating speed-dependent FIR filters to separate the different components. In this paper a new approach is presented using Operational Path Analysis (OPA) to estimate the transfer functions of a Multiple-Input-Multiple-Output (MIMO) model of the tire-road noise contributions based on road…
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