Isolation performance metrics for personal sound zone reproduction systems

Abstract

Two isolation performance metrics, inter-zone isolation (IZI) and inter-program isolation (IPI), are introduced for evaluating personal sound zone (PSZ) systems. Compared to the commonly used acoustic contrast metric, IZI and IPI are generalized for multichannel audio and quantify the isolation of sound zones and of audio programs, respectively. The two metrics are shown to be generally non-interchangeable and suitable for different scenarios, such as generating dark zones (IZI) or minimizing audio-on-audio interference (IPI). Furthermore, two examples with free-field simulations are presented and demonstrate the applications of IZI and IPI in evaluating PSZ performance in different rendering modes and PSZ robustness.

The Effects of Individualized Binaural Room Transfer Functions for Personal Sound Zones

“…Two cases were considered in order to evaluate both aspects of PSZ performance: one in situ case, in which the listener stays at the same position for both the capture of setup BRTFs and the measurement of the performance of generated individualized filters, and one ex situ case, in which the listener is instructed to leave the seat and sit back to the position where the setup BRTFs were measured. This paper presents and extends the authors' prior work [30]: SEC. 1 introduces the PM method and its adaptation used for PSZ filter generation.…”

“…For the human-HATS setup, two types of filters are evaluated within each SZC: To generate PSZ filters, the target pressure in BZ is chosen as the summed responses (truncated to first 2,048 samples) at two ears when a stereo pair of loudspeakers (for the listener, it is the first and fourth loudspeakers from the left, and for the HATS, it is the fifth and eighth loudspeakers) are driven in phase, and the target pressure in DZ is set to zero. In practice, this corresponds to a mono audio program, because it usually leads to higher isolation performance than other multichannel programs [29]. To determine the variance matrix in Eq.…”

“…IZI and IPI indicate the isolation performance of a PSZ system from two complementary perspectives: the isolation between two zones given a single program and the isolation between two active audio programs in the same zone. IZI is conceptually similar to the well-known Acoustic Contrast [12] metric, which is proven to be a special case of IZI for single-channel programs [29]; IPI is more relevant to the perception of audio-on-audio interference [19,33] than IZI and is suitable for scenarios in which multiple programs are simultaneously rendered. Following the general definition, the system setup in this paper corresponds to rendering two mono programs to two zones.…”

“…Such a PSZ setup allows direct measurements and comparison of the Binaural Room Transfer Functions (BRTFs), which consist of HRTFs convolved with room responses, of both the mannequin head and the human listener, as opposed to those in [3,4,[8][9][10] in which larger zones with dense control points are specified. After the BRTFs are measured with in-ear binaural microphones and then used as setup TFs to generate generic and individualized PSZ filters, the performance of the PSZ system were experimentally evaluated with metrics the authors recently proposed in [29]: Inter-Zone Isolation (IZI) and Inter-Program Isolation (IPI), as well as robustness against slight head misalignments.…”