Subjective evaluation of an emerging theory of low-frequency sound source localization in closed acoustic spaces

An earlier reported theory of low-frequency sound-source localization within closed acoustic spaces proposed that virtual image acuity is strongly dependent on sufficient inter-arrival time between a direct sound and its first reflection. This current study aims to test the theory’s predictions by subjective experiment where participants are required to indicate perceived sound source direction, but without knowledge of loudspeaker location. Test signals of frequencies 40 Hz to 115 Hz take the form of either windowed sine or square waves. Results confirm broad agreement with theoretical expectations and support the conjecture, contrary to common expectation, that low-frequency sound localization within the context of closed acoustic spaces is possible, although strongly dependent on system configuration and size of a listening space

Low-frequency sound source localization as a function of closed acoustic spaces

Further development of an emerging generalized theory of low-frequency sound localization in closed listening spaces is presented that aims to resolve the ambiguities inherent in previous research. The approach takes a robust set of equations based on source/listener location, reverberation time and room dimensions and tests them against a set of evaluation procedures to explore image location against theoretical expectations. Phantom imaging is germane to the methodology and its match within the theoretical framework is investigated. Binaural recordings are used to inspect a range of closed environments for localization clues each with a range of source-listener placements. A complementary series of small-scale listening tests are included for perceptual validation

Towards a generalized theory of low-frequency sound source localization

Low-frequency sound source localization generates considerable amount of disagreement between audio/acoustics researchers, with some arguing that below a certain frequency humans cannot localize a source with others insisting that in certain cases localization is possible, even down to the lowest audible of frequencies. Nearly all previous work in this area depends on subjective evaluations to formulate theorems for low-frequency localization. This, of course, opens the argument of data reliability, a critical factor that may go some way to explain the reported ambiguities with regard to low-frequency localization. The resulting proposal stipulates that low-frequency source localization is highly dependent on room dimensions, source/listener location and absorptive properties. In some cases, a source can be accurately localized down to the lowest audible of frequencies, while in other situations it cannot. This is relevant as the standard procedure in live sound reinforcement, cinema sound and home-theater surround sound is to have a single mono channel for the low-frequency content, based on the assumption that human’s cannot determine direction in this band. This work takes the first steps towards showing that this may not be a universally valid simplification and that certain sound reproduction systems may actually benefit from directional low-frequency content

Live sound loudspeaker array optimization for consistent directional coverage with diffuse radiation characteristics.

A central aim of sound reinforcement systems is to deliver consistent tonality across a wide audience area. Loudspeaker arrays are commonly used to meet this goal, where the upper and lower frequency bounds that can be spatially controlled are dictated by inter-element spacing and array width, respectively. This work focuses on the calculation of frequency-dependent complex coefficients for each array element using a modified Fourier technique to achieve a frequency-independent radiation pattern across an array’s functional region. In order to ensure efficiency, temporally diffuse impulses are utilized within the optimization procedure to avoid clustering of radiated energy at the center of an array and to provide a diffuse radiated field while maintaining the desired directional characteristics. Example applications for subwoofer arrays are presented, although the technique is applicable to any frequency range across the audible spectrum.N/

Enhanced wide-area low-frequency sound reproduction in cinemas: effective and practical alternatives to current calibration strategies

The current strategies for the low-frequency calibration of cinema sound systems are based on a flawed premise of low-frequency acoustics and psychoacoustics. This research shows that there is virtually no benefit in terms of spatiotemporal variance reduction: pre- and post-calibrated systems will exhibit equally position-dependent listening experience differences. For modern cinemas, the typical focus on room-modes when designing a low frequency calibration system is not necessary because the dimensions of the space coupled with low reverberation time results in Schroeder frequencies around 35 Hz. Above this value, effects of room-modes are not perceptible. Comb-filtering between sources and low-order reflections is the primary cause of high spatial variance. Furthermore, there is no evidence that spatial averaging techniques used for measurement and equalization are subjectively beneficial. A new approach needs to be invented