# Auralization of High-Order Directional Sources from First-Order RIR Measurements
## 3 Listening Experiment--Comparative Study
### Design and Implementation  
_Measurements_: The underlying measurements are done in the Gyorgy Ligeti Saal (\(V=5630\) m\({}^{3}\), \(T_{60}=1.4\) s) in Graz, Austria. Figure 4 shows a panoramic photo of the measurement setup and Figure 5 the layout of source, receiver, and the locations of the four reflecting baffle (\(0.9\times 1.8\) m) positions. Source and receiver were aligned quasi-parallel to the shorter side walls of the room, are facing each other, and are 4.2 m apart. The source-receiver distance approximately corresponds to the critical distance (\(r_{H}=3.6\) m) when assuming an omnidirectional source, and thus is considered generally interesting. As test signal we used interleaved and exponentially swept sines with a length of 4 s. The measured source and receiver configurations included (i) MOBRIRs ([[https://phaidra.kug.ac.at/o:104386](https://phaidra.kug.ac.at/o:104386)]([https://phaidra.kug.ac.at/o:104386](https://phaidra.kug.ac.at/o:104386))) between the IKO and multiple dummy head orientations (measurements for \(Dy\)), (ii) MIMO RIRs ([[https://phaidra.kug.ac.at/o:104385](https://phaidra.kug.ac.at/o:104385)]([https://phaidra.kug.ac.at/o:104385](https://phaidra.kug.ac.at/o:104385))) between the IKO and the em32 (measurements for \(Em\)), (iii) MIMO RIRs ([[https://phaidra.kug.ac.at/o:104384](https://phaidra.kug.ac.at/o:104384)]([https://phaidra.kug.ac.at/o:104384](https://phaidra.kug.ac.at/o:104384))) between the IKO and ST450 (measurements for \(As\)), and (iv) MIMO RIRs ([[https://phaidra.kug.ac.at/o:104376](https://phaidra.kug.ac.at/o:104376)]([https://phaidra.kug.ac.at/o:104376](https://phaidra.kug.ac.at/o:104376))) between the Cubelet and the ST450 (measurements for \(Sr\), and \(Si\)). Figure 4: Panoramic image (\(360^{\circ}\)) of the measurement setup in the György Ligeti Saal, Graz. The camera perspective corresponds with the receiver/listener position. Tested Directivities:Here, we tested for six distinct beam directions on the horizon \(\varphi_{S}=[0^{\circ},180^{\circ},90^{\circ},45^{\circ},-36^{\circ},-82^{\circ}]\), which roughly correspond to the directions of the back wall, the listener, and the reflectors R1, R2, R3, R4, respectively, cf. Figure 5. Those specific directions were chosen as they evoke a pronounced direct or reflection path and allow for testing certain aspects of the auralization:  
* \(0^{\circ}\): weak direct path, low direct-to-reverberant energy ratio (DRR). * \(-36^{\circ},-82^{\circ},45^{\circ},90^{\circ}\): pronounced reflections and weak direct path. Note that the directions \(\varphi_{S}=-36^{\circ}\) and \(\varphi_{S}=-82^{\circ}\) were perceptually chosen by the authors such that the perception of the baffle reflection (R3, and R4) is most pronounced. In order to avoid redundancy due to symmetry and to test for various reflection vs. direct path levels we also included \(\varphi_{S}=45^{\circ}\) and \(\varphi_{S}=90^{\circ}\) as possible beam directions. * \(180^{\circ}\): pronounced direct path, high direct-to-reverberant energy ratio (DRR). Implementation:For the sake of reproducibility and in order to circumvent room divergence [46; 47; 48], i.e., violation of acoustical expectations arising from the environment in which one listens to headphones, the entire scenery was modeled in virtual reality. In order to deliver graphics as realistically as possible, the room was modeled based on building plans and photogrammetry. Control buttons and labels were added to the virtual environment to give the participants control over the progression of the experimental trials and means to comparatively rate their auditory localization under the various conditions. A screenshot of the user interface is depicted in Figure 6. In addition to the typical playback and save/proceed (upwards facing arrow) buttons we used five colored squares and the corresponding spheres for controlling the experiment.