When a personalized set of head-related transfer functions (HRTFs) is not available, a common solution is identifying a perceptually appropriate substitute from a database. There are various approaches to this selection process whether based on localization cues, subjective evaluations, or anthropomorphic similarities. This study investigates whether HRTF rankings that stem from different selection methods yield comparable results. A perceptual study was carried out using a basic source localization method and a subjective quality judgment method for a common set of eight HRTFs. HRTF rankings were determined according to different metrics from each method for each subject and the respective results were compared. Results indicate a significant and positive mean correlation between certain metrics. The best HRTFs selected according to one method had significant above-average rating scores according to metrics in the second method.

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.

The use of the term 'immersion' to describe a multitude of varying experiences in the absence of a definitional consensus has obfuscated and diluted the term. This paper presents a non-exhaustive review of previous work on immersion on the basis of which a definition of immersion is proposed: a state of deep mental involvement in which the subject may experience disassociation from the awareness of the physical world due to a shift in their attentional state. This definition is used to contrast and differentiate interchangeably used terms such as presence and envelopment from immersion. Additionally, an overview of prevailing measurement techniques, implications for research on immersive audiovisual experiences, and avenues for future work are discussed briefly.