Acoustic contrast, planarity and robustness of sound zone methods using a circular loudspeaker array

Since the mid 1990s, acoustics research has been undertaken relating to the sound zone problem—using loudspeakers to deliver a region of high sound pressure while simultaneously creating an area where the sound is suppressed—in order to facilitate independent listening within the same acoustic enclosure. The published solutions to the sound zone problem are derived from areas such as wave field synthesis and beamforming. However, the properties of such methods differ and performance tends to be compared against similar approaches. In this study, the suitability of energy focusing, energy cancelation, and synthesis approaches for sound zone reproduction is investigated. Anechoic simulations based on two zones surrounded by a circular array show each of the methods to have a characteristic performance, quantified in terms of acoustic contrast, array control effort and target sound field planarity. Regularization is shown to have a significant effect on the array effort and achieved acoustic contrast, particularly when mismatched conditions are considered between calculation of the source weights and their application to the system

Influence of low-order room reflections on sound zone system performance

Studies on sound field control methods able to create independent listening zones in a single acoustic space have recently been undertaken due to the potential of such methods for various practical applications, such as individual audio streams in home entertainment. Existing solutions to the problem have shown to be effective in creating high and low sound energy regions under anechoic conditions. Although some case studies in a reflective environment can also be found, the capabilities of sound zoning methods in rooms have not been fully explored. In this paper, the influence of low-order (early) reflections on the performance of key sound zone techniques is examined. Analytic considerations for small-scale systems reveal strong dependence of performance on parameters such as source positioning with respect to zone locations and room surfaces, as well as the parameters of the receiver configuration. These dependencies are further investigated through numerical simulation to determine system configurations which maximize the performance in terms of acoustic contrast and array control effort. The design rules for source and receiver positioning are suggested, for improved performance under a given set of constraints such as a number of available sources, zone locations and the direction of the dominant reflection. © 2013 Acoustical Society of America

Influence of low-order room reflections on sound zone system performance

Studies on sound field control methods able to create independent listening zones in a single acoustic space have recently been undertaken due to the potential of such methods for various practical applications, such as individual audio streams in home entertainment. Existing solutions to the problem have shown to be effective in creating high and low sound energy regions under anechoic conditions. Although some case studies in a reflective environment can also be found, the capabilities of sound zoning methods in rooms have not been fully explored. In this paper, the influence of low-order (early) reflections on the performance of key sound zone techniques is examined. Analytic considerations for small-scale systems reveal strong dependence of performance on parameters such as source positioning with respect to zone locations and room surfaces, as well as the parameters of the receiver configuration. These dependencies are further investigated through numerical simulation to determine system configurations which maximize the performance in terms of acoustic contrast and array control effort. The design rules for source and receiver positioning are suggested, for improved performance under a given set of constraints such as a number of available sources, zone locations and the direction of the dominant reflection. © 2013 Acoustical Society of America

Personal audio with a planar bright zone

Reproduction of multiple sound zones, in which personal audio programs may be consumed without the need for headphones, is an active topic in acoustical signal processing. Many approaches to sound zone reproduction do not consider control of the bright zone phase, which may lead to self-cancellation problems if the loudspeakers surround the zones. Conversely, control of the phase in a least-squares sense comes at a cost of decreased level difference between the zones and frequency range of cancellation. Single-zone approaches have considered plane wave reproduction by focusing the sound energy in to a point in the wavenumber domain. In this article, a planar bright zone is reproduced via planarity control, which constrains the bright zone energy to impinge from a narrow range of angles via projection in to a spatial domain. Simulation results using a circular array surrounding two zones show the method to produce superior contrast to the least-squares approach, and superior planarity to the contrast maximization approach. Practical performance measurements obtained in an acoustically treated room verify the conclusions drawn under free-field conditions

Innowacyjny układ do sterowania procesem azotowania gazowego zawierający moduł interaktywnego prognozowania rezultatu procesu

The article presents the concept of a system to control the gas nitriding process containing an interactive module for predicting the results of the process on the basis of mathematical model of growth kinetics of the nitrided layer. The concept of the system is based on comparing the current values of process parameters: temperature, the composition of nitriding atmosphere, and the current value of the nitrogen potentia! (which is determined based on the signal from the hydrogen sensor) with a pre-established algorithm of changes in process parameters. According to the developed concept, if there are differences, the control system selects one of two options: - Changing the flow rate of the components of a nitriding atmosphere, in the range of possible changes for a given stand to nitriding, to achieve a predetermined potentia! value, or - Setting a new algorithm for changes in temperature and nitrogen potential. Selecting one of these options by the system will depend on obtaining the slightest difference between on-line calculated result of a process on the basis of mathematical model (for both options) and the assumed result, i.e. the nitrided layer thickness and profile of hardness change.W artykule zamieszczono koncepcję funkcjonowania układu do sterowania procesem azotowania gazowego zawierającego moduł interaktywnego prognozowania rezultatu procesu na podstawie kinetyki wzrostu warstwy azotowanej. Idea działania układu polega na porównywaniu bieżących/aktualnych wartości parametrów procesu temperatury, składu atmosfery i bieżącej wartości potencjału azotowego (wyznaczanego na podstawie sygnału z sondy wodorowej) z założonym wstępnie algorytmem zmian parametrów procesu. Zgodnie z opracowaną koncepcją, w przypadku zaistnienia rozbieżności układ sterowania wybiera jedną z dwóch opcji: - zmienia natężenie przepływu składników atmosfery azotującej w celu osiągnięcia założonej wartości potencjału bądź - wyznacza nowy algorytm zmian temperatury i potencjału azotowego. Wybór jednej z tych opcji przez układ będzie zależał od uzyskania najmniejszej różnicy pomiędzy na bieżąco prognozowanym rezultatem procesu (dla obu opcji) a rezultatem założonym, tj. grubością warstwy azotowanej oraz profilem twardości. Dodatkowo układ będzie zawierał moduł wizualizacji wzrostu grubości stref warstwy azotowanej oraz wizualizację zmian profili twardości w strefie dyfuzyjnej warstwy azotowanej w trakcie trwania procesu

Optimizing the planarity of sound zones

Reproduction of personal sound zones can be attempted by sound field synthesis, energy control, or a combination of both. Energy control methods can create an unpredictable pressure distribution in the listening zone. Sound field synthesis methods may be used to overcome this problem, but tend to produce a lower acoustic contrast between the zones. Here, we present a cost function to optimize the cancellation and the plane wave energy over a range of incoming azimuths, producing a planar sound field without explicitly specifying the propagation direction. Simulation results demonstrate the performance of the methods in comparison with the current state of the art. The method produces consistent high contrast and a consistently planar target sound zone across the frequency range 80-7000Hz. Copyright © (2013) by the Audio Engineering Society

Influence of low-order room reflections on sound zone system performance.

Studies on sound field control methods able to create independent listening zones in a single acoustic space have recently been undertaken due to the potential of such methods for various practical applications, such as individual audio streams in home entertainment. Existing solutions to the problem have shown to be effective in creating high and low sound energy regions under anechoic conditions. Although some case studies in a reflective environment can also be found, the capabilities of sound zoning methods in rooms have not been fully explored. In this paper, the influence of low-order (early) reflections on the performance of key sound zone techniques is examined. Analytic considerations for small-scale systems reveal strong dependence of performance on parameters such as source positioning with respect to zone locations and room surfaces, as well as the parameters of the receiver configuration. These dependencies are further investigated through numerical simulation to determine system configurations which maximize the performance in terms of acoustic contrast and array control effort. The design rules for source and receiver positioning are suggested, for improved performance under a given set of constraints such as a number of available sources, zone locations, and the direction of the dominant reflection

Performance of optimized sound field control techniques in simulated and real acoustic environments.

It is of interest to create regions of increased and reduced sound pressure ('sound zones') in an enclosure such that different audio programs can be simultaneously delivered over loudspeakers, thus allowing listeners sharing a space to receive independent audio without physical barriers or headphones. Where previous comparisons of sound zoning techniques exist, they have been conducted under favorable acoustic conditions, utilizing simulations based on theoretical transfer functions or anechoic measurements. Outside of these highly specified and controlled environments, real-world factors including reflections, measurement errors, matrix conditioning and practical filter design degrade the realizable performance. This study compares the performance of sound zoning techniques when applied to create two sound zones in simulated and real acoustic environments. In order to compare multiple methods in a common framework without unduly hindering performance, an optimization procedure for each method is first used to select the best loudspeaker positions in terms of robustness, efficiency and the acoustic contrast deliverable to both zones. The characteristics of each control technique are then studied, noting the contrast and the impact of acoustic conditions on performance

Performance of optimized sound field control techniques in simulated and real acoustic environments.

It is of interest to create regions of increased and reduced sound pressure ('sound zones') in an enclosure such that different audio programs can be simultaneously delivered over loudspeakers, thus allowing listeners sharing a space to receive independent audio without physical barriers or headphones. Where previous comparisons of sound zoning techniques exist, they have been conducted under favorable acoustic conditions, utilizing simulations based on theoretical transfer functions or anechoic measurements. Outside of these highly specified and controlled environments, real-world factors including reflections, measurement errors, matrix conditioning and practical filter design degrade the realizable performance. This study compares the performance of sound zoning techniques when applied to create two sound zones in simulated and real acoustic environments. In order to compare multiple methods in a common framework without unduly hindering performance, an optimization procedure for each method is first used to select the best loudspeaker positions in terms of robustness, efficiency and the acoustic contrast deliverable to both zones. The characteristics of each control technique are then studied, noting the contrast and the impact of acoustic conditions on performance