## 1 Introduction  
Fully immersive reproduction of spatial audio in a way that both artificial and real audio objects are perceived as plausible audible events in a virtual and/or augmented environment is something researchers have tried for many years. Recently, this has been demonstrated under certain conditions [1]. One method which has been proposed to achieve an auditory illusion of a spatial acoustic environment is via the help of an existing position-dynamic binaural synthesis system [2]. Even then, the occurrence of a plausible auditory illusion depends on many parameters. Beyond an adequate technical realization there are several context dependent quality parameters like congruence between synthesized scene and the listening environment or individualization of the technical system. The goal of our research and this paper is to find efficient solutions to merge real and virtual acoustics in a plausible manner. Our approach is to start with measurements in real rooms and to stepwise simplify these measurements to identify the relevant cues and information which are mandatory to retain plausibility. The advantage of this approach is that we always can compare to the upper reference: The actual measurement in the real scenario. After identifying these cues, measurement efforts can be minimized and the computational efficiency of algorithms to create an auditory augmented reality (AAR) system can be improved. The primary question is to what extent simplifications in the technical realization of an audio-AR system are permissible without leading to an intolerable impairment of spatial auditory perception. In the following, we describe a basic scheme of an AAR system built from several different functional blocks which realize a position-dynamic binaural synthesis. This includes:  
1. provision of binaural room filters from measurements or simulations,
2. representation of the scene,
3. creation and/or adaptation of binaural room filters related to the pose and position of the listener, and
4. real-time rendering to make a position-dynamic auralization possible. Figure 1 shows these blocks in a basic scheme. In each block, different techniques and approaches are listed. Bold entries are techniques which will be described in greater detail. The reproduction of an audio object in a reverberant room can be realized using BRIRs. The audio signal of the source is convolved with binaural room impulse responses (BRIRs) of the current source-receiver position and head orientation of the listener. For the acquisition of binaural room filters, several popular approaches exist. BRIRs can be simulated [3,4] or directly measured, for example, with a dummy head. To create a position and head-pose-dependent binaural synthesis, measurements for each dummy head orientation and position must be conducted. The separation of the head-related transfer functions (HRTFs) and room measurements reduces the effort significantly. One way to do this is to just measure the room impulse responses (RIRs) and to estimate or measure the direction of arrival (DOA) in a separate calculation or measurement. An estimation can be done by assuming a certain room geometry, such as a shoe-box model, and by assigning a direction to the measured reflections [5]. Information about the room can either be predefined or measured by other sensors (visual, radar, etc.). The DOA can also be measured with an appropriate microphone array. Once the DOA is available, a direction and an HRTF can be assigned to each reflection and a BRIR can be calculated. The Spatial Decomposition Method (SDM) is one approach in this domain [6,7]. An alternative way is to employ B-format or higher order ambisonic arrays to record transfer functions in the ambisonics signal representation. The spatial resolution directly depends on the number of microphones as well as on the array design. To create binaural signals the combination with a spherical HRTF data set is necessary as well [8]. The next step is the creation of a scene.