由于发动机小型化倾向加剧及废气排放法规日益严格,在发动机和汽车的开发过程中,必须对噪声品质进行检验.基于这一原因,近几年,AVL公司致力于燃烧爆震指数及粗暴指数等参数的开发,运用这些参数,就能在整个开发过程中脱机检验噪声品质,而不是仅靠主观评定.

Extact knowledge of chassis transmission paths is essential for an effective and purposeful interior noise / noise quality development process. One possible approach to obtain this required information is the application of a Transfer Path Analysis (TPA).When applying this analysis method care has to be taken in choosing the appropriate algorithm and the corresponding setup. Therefore this paper first focuses on the most important errors concerning existing TPA methodologies and their consequences on the result, starting from difficulties in locating the excitation position of the applied forces via deviations in excitation direction up to differences in chassis temperatures.Accordingly solutions for elimination or reduction of these errors are presented. Additionally a completely new TPA approach is introduced which is faster and more accurate than currently approved methods.

The proposed system enables the control of sound sources in a large auditorium both in direction and distance. Reproduction of 3D sound fields over loudspeakers where distance coding is taken into account is a rather difficult goal, because different simple and complex properties of a sound event contribute to the perception of distance. Similar to the perception of pitch, the perception of distance is bounded in both directions. Small deviations concerning far and very short distances can hardly be distinguished. Furthermore, caused to be the associated memory, the impression of distance is always biased and relative. Therefore, similar to the visual sense, the auditory sense can be easily confused. To overcome these problems the reproduces sound field should be identical to the natural one as much as possible. As will be shown below, the presented approach is based on the construction of the wavefront curvature in a defined listening area in order to perceive the desired distance. The subject of this paper is to find out and validate objective description, which correlates with subjective perception. Based on this correlation, optimization criteria can be evaluated to maximize the reconstruction performance in order to control the desired spatial auditory stimuli of perception.

Concerning the spatialisation of 3D sound fields around an almost free mobile listener an immersive audio environment for desktop applications is presented. The sound field is reproduced by a loudspeaker array that is positioned along the desktop edges. To improve the listener's freedom no head tracking is required. Using the principle of the wave field synthesis approach combined with different panning techniques derives the loudspeaker signals. Therefore virtual sources can be positioned in azimuth, elevation and distance, too. The reproduction area around the listener and the possible source space is restricted to a defined area. The effort of these different panning techniques can be simulated and objectively compared.

Convincing binaural sound reproduction via headphones requires filtering the virtual sound source signals with head related transfer functions (HRTFs). Furthermore, humans are able to improve their localization capabilities by small unconscious head movements. Therefore it is important to incorporate head-tracking. This yields the problem of high-quality, time-varying interpolation between different HRTFs. A further improvement of human localization accuracy can be done by considering room simulation yielding a huge amount of virtual sound sources. To increase the computational efficiency of the proposed system, a virtual ambisonic approach is used, that result in a bank of time-invariant HRTF filter independent of the number of sources to encode.

A mathematical model is presented to objectively derive sound localisation performance using HRIR (Head Related Impulse Response) based binaural sound reproduction systems. Rendering a sound source via panning methods causes artefacts that will lead to errors in localisation by human subjects. A localisation function and a localisation blur will be derived by comparing reference HRIRs with the distorted HRIRs, assuming that the cues specified by the reference HRIRs result in optimal localisations. Psychophysical effects will be incorporated as well. Studying the relationship between panning and perceived directions using listening tests entails an enormous effort of time. In addition, the presented mathematical model can be used to minimise the number of parameters which need to be evaluated by listening tests. Furthermore the localisation performance of several HRIR-based panning methods will also be evaluated.

In general hearing tests are necessary to assess the properties of spatialisation systems. To speed up the procedure of testing different system parameters an objective model of localisation in binaural sound reproduction system is introduced [7]. In the following the localisation properties of an auditory system based on playback via head phones is investigated. Therefore a new design for the experiment setup to investigate the perception of virtual sources is introduced. This paper reports the subjective validation of the objective model by informal listening tests. In addition to the localisation and localisation blur further properties are evaluated. Significant differences between different system setups are studied and depicted.

This investigation proposes a possibility to synthesise a true 3D sound field over loudspeakers. A new approach concerning the distance coding is presented. We tried to combine the benefits of using both the wave field synthesis (WFS) approach and higher order ambisonics (HOA). Therefore the proposed system can be divided into two main parts. Firstly the determination of the driving functions of the sound sources using a derivative of the WFS approach. Secondly the coding for transmission and/or storage whereby the scheme is based on the ambisonics approach using higher orders. The paper is organised in four sections. The first section gives a brief introduction about the WFS and the HOA approaches. In the second section the derivation of the driving functions is presented and the coding scheme of the derived source signals is explained. Results are given irk section three. Finally the paper is concluded and further possible research directions are identified.