Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S7/00—Indicating arrangements; Control arrangements, e.g. balance control
  • H04S7/30—Control circuits for electronic adaptation of the sound field
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S2400/00—Details of stereophonic systems covered by H04S but not provided for in its groups
  • H04S2400/11—Positioning of individual sound objects, e.g. moving airplane, within a sound field
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S2420/00—Techniques used stereophonic systems covered by H04S but not provided for in its groups
  • H04S2420/11—Application of ambisonics in stereophonic audio systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S2420/00—Techniques used stereophonic systems covered by H04S but not provided for in its groups
  • H04S2420/13—Application of wave-field synthesis in stereophonic audio systems

Definitions

• Advantages of the former include versatility of the spatial source layout and in the number of sources required, with the inherent limitations in performance due to a given configuration.
• the source configuration in relation to synthesis methods tends to be more constrained, especially in the case of methods like Wave Field Synthesis and Ambisonics.
• these methods facilitate reproduction of a specific sound field, which enables control of impinging wave fronts in the controlled regions, unlike the energy considerations applied in most numerical optimization methods as in the Acoustic Contrast Control (ACC) and the Energy Difference Maximization method (EDM).
• ACC Acoustic Contrast Control
• EDM Energy Difference Maximization method
• control strategies including elements from both synthesis and optimization approaches exist.
• the Pressure Matching method is an example of this type of control strategy.
• IVSSP Independent Multimedia Processing
• control the acoustic potential energy in each zone this energy may be seen as being proportional to the mean square sound pressure in a zone
• the weight determining step comprises determining a weight for controlling the tradeoff between the cost functions in the combined optimization.
• the cost functions may be an unconstrained optimization given as:
• this reproduction error may be a difference between a direction of a sound wave and a preferred direction and/or a difference between an ideal plane wave and the form of the actual wave.
• the Acoustic Contrast is defined as the ratio of the average potential energies in the two zones, which is proportional to the average squared pressures in the zones.
• the EDM does not include a matrix inversion to determine the source weights
• Figure 1 illustrates one embodiment of a system configured to use the method of the invention, the system having an equidistant circular array of sources 2, which encompasses the desired sound zones, is applied.
• the schematic setup of zones and sources is shown using the polar coordinate system.
• the spatial sound regions to be controlled are inside a circular array of 40 acoustic monopoles.
• the dark zone refers to a region with low sound pressure relative to the bright zone, where high sound pressure is desired.
• the system also has a controller or processor 10 configured to receive sound or signals from one or more sources and to generate signals for the speakers 2 in accordance with the method in order to obtain the desired sound in the two zones.
• This controller may thus have filters, delay circuits and/or amplifiers either for more speakers 2 or individually for each speaker 2.
• each speaker 2 could alternatively have its own amplifier/delay circuit/filter, if desired.
• the bright and dark zones are distinguished by applying different amplitude of the plane wave in the zone (the amplitude of the plane wave in the dark zone is e.g. reduced by 60 dB).
• the Pressure Matching term in the hybrid method is unnecessary for the Pressure Matching term in the hybrid method to include control points in the dark zone, where the main criterion is low sound pressure level rather than accurate wave front reproduction. Therefore, the Pressure Matching control points in the hybrid method only include points in the bright zone in order to reduce the restrictions on the solution.
• Figure 2 displays the Acoustic contrast obtained with Energy Difference Maximization at different values of the control factor ⁇ .
• the performance obtained by the Acoustic Contrast Control is included for reference. The values are obtained at 1 kHz for the configuration shown in Fig. 1 .
• Experimental data are disclosed, the data related to a simulation of one embodiment of the invention.
• the simulation was conducted under anechoic conditions and without any scattering elements.
• the EDM, ACC, and the proposed hybrid method were implemented with a 3D acoustic monopole simulation and evaluated in the plane coinciding with a circular source array of radius 1.5m and sound zone radius of 0.3m. Simulations employing 40 equidistant monopoles were made at different frequencies in the range 100-2500 Hz.
• the acoustic contrast was evaluated as well as the reproduction error, where the latter was only applied for the EDM and hybrid method due to the fact that no desired phase characteristics are implied in the ACC.
• Figure 3 displays two-dimensional plots of the plane of concern at 1 kHz, where the upper row shows the normalized level and the lower shows the real part of the complex sound field showing the performance of ACC, PM and the hybrid method when generating a bright and a dark zone each with a radius of 0.3m and a separation distance of 1 .2m at 1 kHz.
• An array of 40 three-dimensional monopole sources on a circle of 1.5m was simulated.
• the surface plot is showing the plan coinciding with the source array.
• the dark regions on the level plots are seen to spatially extend further and the low sound pressure extends far beyond the predefined regions.
• the dark region is found to nearly overlap the space of the bright zone introducing spatial variations across this area, which is highly unintended. Both the Pressure Matching and the hybrid method provide more even distribution of sound energy in the bright zone.
• the hybrid method performs better compared to the Pressure Matching method below approximately 1750 Hz in the given configuration and appears to converge towards the Pressure Matching method at higher frequencies.
• the resulting contrast obtained with the hybrid drops rapidly above 1200 Hz, where the main effort is focused on preserving a low reproduction error rather than high contrast, since opti- mum including both high contrast and low reproduction error seems unachievable in this frequency interval.
• the system may have one or more microphones 4 (figure 1 ) for setting up the model and deriving the parameters and/or for permanent or intermittent use, when parameters are to be altered or the listening space, furnitures, listening position(s), zone positions, speaker positions or the like are altered.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Stereophonic System (AREA)
• Circuit For Audible Band Transducer (AREA)
• Soundproofing, Sound Blocking, And Sound Damping (AREA)

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• 2013
  • 2013-03-14 EP EP13711865.9A patent/EP2826264A1/en not_active Withdrawn
  • 2013-03-14 WO PCT/EP2013/055249 patent/WO2013135819A1/en not_active Ceased
  • 2013-03-14 CN CN201380012369.8A patent/CN104170408B/zh active Active
  • 2013-03-14 US US14/381,089 patent/US9392390B2/en active Active
  • 2013-03-14 JP JP2014561452A patent/JP6069368B2/ja active Active
  • 2013-03-14 KR KR1020147028535A patent/KR102024284B1/ko active Active

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