# Binaural Rendering with Measured Room Responses: First-Order Ambisonic Microphone vs. Dummy Head
## 1 Introduction  
Typically, binaural rendering involves a convolution of source signals with measured or modeled head-related impulse responses (HRIRs) or binaural room impulse responses (BRIRs) and playback of the corresponding ear signals via headphones [1]. Both HRIRs and BRIRs implicitly contain the cues accessible to the human auditory system to perceive sound from a certain direction and distance, with a certain source width, envelopment, or spaciousness, cf. [2, 3]. In order to reduce poor externalization when using both individual and non-individual HRIRs, it is often helpful to involve a natural or simulated acoustic room and thus to render with BRIRs instead. It is shown in [1, 4] that BRIRs measured with a loudspeaker and a dummy head can achieve static binaural rendering of high audio quality and of convincing realism. Such a BRIR-based virtualization of loudspeakers in rooms is not only useful to virtualize multi-channel loudspeaker setups in mixing studios [5, 6, 7], but also to document and preserve acousmatic or electroacoustic music sceneries. By involving the natural interaction of the ear signals with the head rotation of a listener, i.e., head-tracking [8] and dynamic rendering, immersion is improved as this reduces localization ambiguities and poor externalization [9, 10, 11]. Dynamic and interactive head-tracked BRIR rendering requires the acquisition of MOBRIRs (multi-orientation BRIRs), which can be tedious for highly resolved orientations. For best individualized results, in particular, one would need to measureMOBRIRs of each individual listener in each room to be auralized. Efficient and versatile alternatives [12; 13; 14] propose to measure the listener-dependent (HRIRs) and room-dependent (RIRs) parts separately to enable individualization as a second step. _State of the art:_ Linear interpolation of coarse-orientation MOBRIRs can cause strong comb-filter artifacts. [PERSON] [15] showed for multiple-orientation binaural recordings that the minimum required binaural grid resolution to avoid artifacts is most sensitive in anechoic conditions, and less sensitive reverberant cases, in which particular reverberation did not matter. To ensure continuous and robust interpolation from orientations coarser than 3\({}^{\circ}\), a dual-band interpolation strategy is required, which literature refers to as motion-tracked binaural (MTB) [16]. At low frequencies, the dual-band approach interpolates the headphone signal from neighboring pairs of recorded ear signals linearly, while comb filters at high frequencies are avoided by combining interpolated spectral magnitudes with suitable phase values, e.g., found by spectrogram inversion [17]. Less challenging approaches yielding a suitable phase are discussed in [18] and perceptual properties are studied in [19]. Perceptually optimal cross-over frequencies and block sizes were investigated in [20] for the static and dynamic case, with which rendering from MOBRIRs resolved finer than 30\({}^{\circ}\) was found to be indiscernible from a 1\({}^{\circ}\)-resolved reference. Dynamic rendering based on first-order Ambsonic RIRs (ARIRs) and a pre-measured set of high-resolution HRIRs, e.g., of a dummy head [21], is studied in [22]. Static rendering with ASDM (Ambisonic Spatial Decomposition Method) upscaling was shown to yield perceptually indistinguishable results for 7 th order when compared to a reference dummy-head BRIR. Moreover, the study involved three rooms of different reverberation times (0.3 s, 0.7 s, and 1.4 s) and could show that the performance of the ASDM method did not depend on the particular reverberation time. _Contents:_ ARIR-based and MOBRIR-based rendering haven't been compared yet, and our contribution deals with establishing a balanced comparison. The goal is to find out configurations in which both methods yield perceptually optimal or correspondingly scaled results.