## 1 Introduction
Generally, the auralization process consists of three modules [2]. The first module provides the signal emitted at the source. In its simplest form, this emission module makes use of suitable audio recordings. Obviously, the disadvantage of this strategy is its inflexibility, the limitations with respect to possible emission signal variations and the fundamental difficulty to obtain recordings that are not contaminated by unwanted sound. In addition, due to the Doppler effect, recordings of moving sources can be used for the auralization of situations with similar geometries only. It is therefore promising to use a digital emission synthesizer that is capable of generating the audio signal as radiated by the source. In [5], a granular synthesis using an enhanced pitch-synchronous overlap-and-add (PSOLA) method is presented for engine noise. This method features low computational costs and is therefore well suited for real-time applications. It is however limited in terms of flexibility, as it does not allow for inter- and extrapolations between measured signals. This limitation can be overcome by the synthesizer presented in this article, at the expense of computational costs. The second module needed in the auralization process is a filter that simulates the sound propagation effects of the wave traveling from the source to the receiver. These effects involve geometrical spreading, propagation delay and atmospheric absorption. In outdoor situations, along with the direct sound path, also reflections occur, particularly ground reflections, leading to the ground effect. When either the source or the receiver moves, additionally, the Doppler effect arises. However, also, due to the time-varying propagation situation, all of the other effects change over time, which means that the propagation filter becomes time variant [18]. The third module is a reproduction system, which renders the received signals to headphones or a multi-channel loudspeaker system. In this process, for every received signal, its corresponding emission angle with respect to the observer is required. For the rendering, a variety of different methods exists [19]. Further, it has to be assured that the reproduction system has a linear frequency response and that it is correctly calibrated. In the ongoing research project \"TAURA\", a traffic noise auralizator is developed that covers road traffic and railway noise. It will form the basis for future experiments to refine the characterization of noise. The key element is a synthesizer that simulates the acoustical emission of a great many different vehicles, operating on a wide variety of surfaces and under different operating conditions. In the TAURA model, road traffic noise is created by the superposition of individual vehicle pass-by sounds. The objective of this article is to describe how these single pass-by sounds can be generated in the case of passenger cars. This paper extends the work presented in [20] and is structured in two main parts: In Section 2, the auralization model of accelerating passenger cars is developed step by step and presented. Thereby, an emission synthesizer, which is based on spectral modeling synthesis, and propagation filtering algorithms are elucidated. Section 3 shows how the model parameters can be estimated based on controlled measurements. On that account, a series of signal analysis steps to obtain the steering parameters of the synthesizer is proposed. The article ends with conclusions in Section 4.