Stephan Brandl

Sound Optimization for Downsized Engines

Today, the number of downsized engines with two or three cylinders is increasing due to an increase in fuel efficiency. However, downsized engines exhibit unbalanced interior sound in the range of their optimal engine speed, largely because of their dominant engine orders. In particular, the sound of two-cylinder engines yields half the perceived engine speed of an equivalent four-cylinder engine at the same engine speed. As a result when driving, the two-cylinder engine would be shifted to higher gears much later, diminishing the expected fuel savings. This chapter presents an active in-car sound generation system that makes a two-cylinder engine sound like the more familiar four-cylinder engine. This is done by active, load-dependent playback of signals extracted from the engine vibration through a shaker mounted on the firewall. A blind test with audio experts indicates a significant reduction of the engine speed when shifting to a higher gear. In the blind test, experts favored the interior sound of the proposed sound generation system and perceived better interaction with the vehicle.

Efficient and accurate determination of the transfer characteristics of vehicle bodies

An evaluation of the complex properties of the NVH transfer of a vehicle body is done by transfer path analysis (TPA). Result quality is mainly depending on measurement technology and the applied mathematical models. AVL List GmbH developed a new promising approach during a research project and presents the simulation tool TPA-Form, which allows a remarkable increase in efficiency and result quality.

Effiziente und exakte Bestimmung der Uebertragungscharakteristiken von Fahrzeugkarosserien

Die Ermittlung komplexer ubertragungseigenschaften einer Fahrzeugkarosserie wird unter anderem mittels der Transferpfadanalyse (TPA) durchgefuhrt. Die Qualitat der Ergebnisse ist dabei stark von der messtechnischen Erfassung und der mathematischen Modellierung bestimmt. Die AVL List GmbH entwickelte neue erfolgversprechende Ansatze innerhalb eines Forschungsprojekts und stellt das Simulationswerkzeug TPA-Form vor, mit dem eine deutliche Steigerung der Effizienz und Gute der Ergebnisse erreicht werden kann.