Auralization of High-Order Directional Sources from First-Order RIR Measurements

Abstract

Can auralization of a highly directional source in a room succeed if it employs a room impulse response (RIR) measurement or simulation relying on a first-order directional source, only? This contribution presents model and evaluation of a source-and-receiver-directional Ambisonics RIR capture and processing approach (SRD ARIR) based on a small set of responses from a first-order source to a first-order receiver. To enhance the directional resolution, we extend the Ambisonic spatial decomposition method (ASDM) to upscale the first-order resolution of both source and receiver to higher orders. To evaluate the method, a listening experiment was conducted based on first-order SRD-ARIR measurements, into which the higher-order directivity of icosahedral loudspeaker’s (IKO) was inserted as directional source of well-studied perceptual effects. The results show how the proposed method performs and compares to alternative rendering methods based on measurements taken in the same acoustic environment, e.g., multiple-orientation binaural room impulse responses (MOBRIRs) from the physical IKO to the KU-100 dummy head, or higher-order SRD ARIRs from IKO to em32 Eigenmike. For optimal externalization, our experiments exploit the benefits of virtual reality, using a highly realistic visualization on head-mounted-display, and a user interface to report localization by placing interactive visual objects in the virtual space.

Parametric Late Reverberation from Broadband Directional Estimates

“…Applying the PIV is especially straightforward if first-order Ambisonics room impulse responses (ARIR) are available. In broadband methods employing PIV estimation [4], [16], [17], the omnidirectional pressure is simply multiplied with the three first-order directional components sample-by-sample. The resulting vector's length can be interpreted as an estimate of diffuseness, which in turn is used in narrowband processing of SRIR [1] and in the parametric time-frequency spatial audio method DirAC [18], which operates on running signals.…”

“…Firstly, it has been observed that the rendered response may contain more high frequencies than the omnidirectional response, which can be referred to as whitening. The effect has first been reported in [29] and the typical solution is to apply spectrogram or filterbank-based time-varying equalization to the response [17], [29]. If such equalization is not done carefully, it can lead to audible artefacts of its own.…”

Common-Slope Modeling of Late Reverberation

“…For directional sound sources and receivers, it is also important to consider the propagation path's direction of departure (DOD) from the source and direction of arrival (DOA) at the receiver [35]. They are denoted by Ω s = (ϕ s , θ s ) and Ω r = (ϕ r , θ r ), respectively, where ϕ is the azimuth angle and θ is the elevation angle.…”

Common-slope modeling of late reverberation

“…A room impulse response (RIR) describes the combined effects on sound waves traveling from a sound source at position x s = (x s , y s , z s ) to a receiver at position x r = (x r , y r , z r ). For directional sound sources and receivers, it is also important to consider the propagation path's direction of departure (DOD) from the source and direction of arrival (DOA) at the receiver [43]. They are denoted by Ω s = (ϕ s , θ s ) and Ω r = (ϕ r , θ r ), respectively, where ϕ is the azimuth angle and θ is the elevation angle.…”