Patent Grant
11363400
This application is the U.S. National Stage of International Application No. PCT/DE2019/100214 which designated the United States and has been published as International Publication No. WO 2019/196975 A1 and which claims the priority of German Patent Application, Serial No. DE 10 2018 108 852.3 filed Apr. 13, 2018, pursuant to 35 U.S.C. 119(a)-(d) the description of which is hereby incorporated by reference.
The invention relates to a method for influencing an auditory direction perception of a listener, wherein a focused sound is emitted by a real source S1 having a directional effect, which reaches the listener in a direct way between the real source S1 and the listener at a time t1 as a direct sound component and after at least one reflection from a direction different from the direction of the real source S1 at a time t0 as a reflected sound component.
The invention also relates to an arrangement for implementing the method for influencing an auditory direction perception of a listener.
Localization masking is intended to obscure for a listener the direction of the sound of a real source of a sound-projecting audio playback system. At the same time, the perception of the direction of the listener in a direction other than the direction of the real source is to be intensified.
Sound-projecting audio playback systems are formed by one or more real sources with, for example, high directivity, which are located in a room with sound-reflecting boundary surfaces. A real source can include one or more sound transducers, such as loudspeakers. Such sound-reflecting boundary surfaces are, for example, walls, windows and doors. By emitting strongly focused sound beams through the real sources, targeted reflections at these sound reflecting boundary surfaces can be generated. So-called virtual sources are formed by one of these reflections or by a combination of several reflections.
With sound-projecting audio playback systems of this type, an auditory direction perception of, for example, sounds or instruments can be shifted away from the real source by using targeted reflections.
The achievable directivity of real sources is physically limited by their limited size and by the number of the sub-elements involved in the sound radiation. Further explanations are given, for example, in OLSON, H.: Acoustical Engineering. D. Van Nostrand Company INC., Princeton, N.J., Toronto, New York, London, 1957.
The resulting focusing power is frequency-dependent and limited to a medium frequency range.
The auditory perception of the listener is influenced not only by projected sound from the direction of one or more virtual sources, but also by the direct sound arriving directly from the direction of one or more real sources. This direct sound does not propagate along reflection paths and therefore reaches a listener earlier than the projected sound.
Depending on the frequency-dependence of the focusing power, the spectral composition and the total energy of the two sound components are different. Depending on its spectral composition and the total energy remaining, direct sound can dominate the auditory direction perception of a listener. The precedence effect then localizes for a listener, for example, a sound or an instrument in the direction of the real source(s). Alternatively, the hearing event of the listener may be broken down into components arriving from different directions. Such scenario is disclosed, for example, in Wühle, T; Merchel, S.; Altinsoy, M.: Evaluation of auditory events with projected sound sources using perceptual attributes. In: Audio Engineering Society 142nd Convention, 2017, or Wühle, T.; Altinsoy, M.: Investigation of auditory events with projected sound sources. In: 173rd Meeting of Acoustical Society of America and 8th Forum Acusticum, 2017.
Real sources of sound-projecting audio playback systems are mostly formed by so-called loudspeaker arrays, in which several loudspeakers or sound converters are arranged next to one another and/or one above the other. No focusing can be achieved for frequencies smaller than a certain lower cut-off frequency, due to the ratio of the size of a loudspeaker array to the wavelength of the emitted sound. For frequencies greater than a certain upper cut-off frequency, the focusing power collapses frequently due to so-called spatial aliasing. In spatial aliasing, new main lobes form at the frequency depending on the ratio of a loudspeaker distance to the wavelength of the emitted sound, which with increasing frequency migrate towards the original main lobe.
In order to optimize the focusing properties of such loudspeaker arrays, numerous approaches have already been established in the prior art. For example, special loudspeaker arrangements and/or corresponding signal processing for optimizing the focusing performance with regard to the frequency range, achievable side-lobe attenuation and/or reduction of spatial aliasing are known.
Solutions from this state of the art can be found in KLEPPER, D.; STEELE, D.: Constant Directional Characteristics from a Line Source Array. In: Journal of the Audio Engineering Society 11 (1963), July, No. 3, pp. 198-202, MOSER, M.: Amplitude and phase controlled acoustic transmission lines with uniform horizontal directionality. In: Acustica 60 (1986), April, No. 2, pp. 91-104, VAN DER VAL, M.; START, E.; DE VRIES, D.: Design of Logarithmically Spaced Constant Directivity Transducer Arrays. In: Journal of the Audio Engineering Society 44 (1996), June, No. 6, pp. 497-507 and VAN BEUNINGEN, G.; START, E.: Optimizing Directivity Properties of DSP controlled Loudspeaker Arrays. In: Reproduced Sound 16 Conference, Statford (UK), 2000.
Further examples can be found in KEELE JR., D.: The Application of Broadband Constant Beamwidth Transducer (CBT) Theory to Loudspeaker Arrays. In: Audio Engineering Society Convention 109, 2000, or KEELE JR., D.: Implementation of Straight-Line and Flat-Panel Constant Beamwidth Transducer (CBT) Loudspeaker Arrays using Signal Delays. In: Audio Engineering Society Convention 113, 2002.
With particular mechanical arrangements of individual loudspeakers and/or additional digital processing of their control signals, a more homogeneous focusing behavior is achieved, particularly in the middle frequency range, or the effect of spatial aliasing is reduced. Such approaches are also known as “constant beamwidth” approaches.
Also known are so-called “superdirective” approaches, which enable comparatively strong focusing and expand the effective frequency range of the focusing slightly to low frequencies. A respective discussion can be found in BITZER, J.; SIMMER, K.: Superdirective Microphone Arrays. In: BRANDSTEIN, M. (ed.); WARD, D. (ed.): Microphone Arrays. Springer Verlag, 2001, pp. 19-37 and GÁLVEZ, M F S; ELLIOTT, S J; CHEER, J.: A Superdirective Array of Phase Shift Sources. In: Journal of the Acoustical Society of America 132 (2012), June, No. 2, p. 746.
In addition to the radiation of focused sound bundles, modern sound-projecting audio playback systems use filtering based on a head-related transmission function (HRTF) of sound components that are either directly or indirectly radiated via projection, in order to produce at the listener a localization deviating from the direction of the real source. The so-called head-related transfer function (HRTF) or outer ear transfer function describes a complex filter effect in which a person's head, outer ear and torso are involved.
An application of HRTF filtering is based on measurements of the directional behavior of the outer ear. This directional behavior imprints on the sound a frequency response, which the sound would have if it would arrive at the listener from a certain direction. For example, the proportion of high frequencies can be reduced to create the illusion that the sound is emitted from a position behind the listener. In this way, the perception of sound can be supported in a certain direction. Approaches of this type are known, for example, from U.S. Pat. No. 9,674,609 B2.
Conventional sound-projecting audio playback systems, where the generation of virtual sources is based solely on the use of reflections, are fundamentally limited to a medium effective frequency range due to physical restrictions. The physical dimension of the array affects the lower cut-off frequency due to a lack of ability to concentrate the sound at long wavelengths, while the mutual distance between the speakers affects the upper cut-off frequency (spatial aliasing).
Complex signal processing approaches to improve the absolute focusing performance and/or to expand the frequency range are particularly susceptible to irregularities within the individual channels, as discussed in Cox, H.; Zeskind, R.; Kooij, T: Practical Supergain. In: IEEE Transactions on Acoustics Speech and Signal Processing 34 (1986), June, No. 3, pp. 393-398 and Mabande, E.; Kellermann, W.: Towards Superdirective Beamforming with Loudspeaker Arrays. In: Conf. Rec. International Congress on Acoustics, 2007.
Even minimal fluctuations in the installation position of the loudspeakers or production-related deviations in the transmission behavior of the individual loudspeakers can often prevent the theoretical performance of such approaches from being achieved in practice. As a result, localization in the direction of the real source can only be suppressed for playback having certain spectral and temporal properties.
Spectral properties are to be understood as referring to the frequency components of a signal.
Temporal properties are to be understood as referring to a time profile of a signal, such as a sound pressure-time profile.
The underlying data for HRTF-based filtering for sound components emitted directly or indirectly via projection, as is used in complex sound-projecting audio playback systems, are mostly based on measurements on an artificial head or on averaging over a comparatively small number of measurements on test subjects. These data may differ significantly from the individual head-related transmission functions of the listener, which limits the achievable effect. If a virtual source is generated jointly by sound projection and HRTF-based filtering, the resulting mixed products can cause an incorrect localization or entirely prevent a clear localization in the superposition of the corresponding sound components.
There is therefore a need for a solution that overcomes the disadvantages of the prior art and enables improvement of the suppression of the auditory localization in the direction of one or more real sources of a sound-projecting audio playback system.
In contrast to absolute masking, this is not about making the real source inaudible, but exclusively about preventing the perception of the direction of the real source, which can also be called localization masking.
This is particularly interesting when a limited absolute focusing power and the physically limited frequency range of one or more real sources complicate or prevent sound projection using classic methods.
The object of the invention is now to provide a method for influencing an auditory direction perception of a listener and an arrangement for implementing the method, with which the suppression of the auditory localization of a direction of one or more real sources of a sound-projecting audio playback system can be improved. In this way, the perception of a listener of an auditory direction is to be shifted away from a real source.
The object is achieved by a method for influencing an auditory direction perception of a listener comprising emitting a focused sound by a real source S1 having a directional effect and reaching the listener on a direct path between the real source S1 and the listener at a time t1 as a direct sound component and after at least one reflection from a direction that is different from the direction of the real source S1 at a time t0 as a reflected sound component, generating an additional localization-masking sound instance radiated by the real source S1 with a directional effect in a defined direction.
The object has been achieved by and arrangement for implementing the method for influencing an auditory direction perception of a listener including a localization masking processor for generating the at least one additionally generated, localization-masking sound instance, that the localization masking processor comprises a first input for parameters L(f), Δt, ϑ, φ for each direct and each projected transmission channel, a second input for a playback signal x(t) with a desired localization direction ϑLok; φLok, and an output for outputting control signals y(t) and their radiation direction ϑBeam; φBeam, and that the output is connected to a sound projecting audio playback system. Further embodiments are also disclosed.
To suppress the auditory localization of a direction of a real source of a sound-projecting audio playback system, it is provided to generate at least one additional sound instance, which a listener perceives as at least one virtual sound source from a direction deviating from the real source. By generating this additional sound instance such that this additional sound instance arrives at the listener before the sound of the real source and by exploiting the precedence effect, the localization in the direction of the real sound source is suppressed, thus shifting the localization. This process is also referred to as localization masking and thus differs from an absolute masking. The goal with absolute masking is to make certain sound components inaudible.
To implement the method, the concrete playback situation is first characterized by measuring or calibrating the surroundings. For this purpose, the impulse responses of the direct and projected sound transmission paths can be determined in a specific and spatially limited playback area. This can be performed with a measuring system or based on geometric, acoustic or electroacoustic models of the playback room and real source.
The complex frequency responses L(f) of the transmission paths are then derived, as are the associated delay times Δt, with which the sound components from the direction of the virtual source arrive at the listener by way of at least one reflection with respect to the sound components that arrive directly from the direction of the real source. Although this description refers for sake of simplification to a real source and a virtual source, a person skilled in the art will understand that this will also apply to several real sources and several virtual sources. For example, a virtual source can be formed by a single reflection point. Alternatively, a virtual source can be formed, for example, by two or more reflection points. In one example, a virtual source can be formed intermediate on a path between two reflection points.
The complex frequency responses have a magnitude and a phase and thus enable an unambiguous characterization based on the impulse response defined in the time domain.
Based on these data, for example, a so-called localization masking processor generates additional sound instance which arrives at the listening position from the direction of a reflection, for example shifted by a defined time ΔtM.
When using a reflection path, on which the sound of the additional sound instance is reflected, for example on walls inside a room, the additional sound instance reaches the listener from a direction that is different from the radiation direction. Thus, for example, a sound event can be generated that arrives from the side or from an area behind the listener. For example, since a property and the geometry of a room is known from a calibration of the surroundings, a desired effect, such an effective sound arriving from the right rear, can be produced for the listener by emitting sound in a defined direction.
The intention is to control the radiation of the additional sound instance in the time domain. With the knowledge of the reflection path, the time control can be adjusted such that the additional sound instance arrives at the listener earlier and thus enables localization masking of the real source.
In an alternative embodiment, the localization masking processor may generate several additional sound instances which arrive at the position of the listener from different directions of the reflections, each shifted by defined time differences ΔtM. The time differences ΔtM between the plurality of additional sound instances can here be identical or different from each other.
Compared to playback without localization masking, an absolute delay can thus be generated, which is made possible by buffering the playback signal.
In addition, one or more additional sound instances may be pre-distorted and hence have, as a result of focusing-dependent frequency-dependent amplitude attenuation, for example the same complex frequency response as the original direct sound.
According to the so-called precedence effect, which is also referred to as the “law of the first wave front”, when the same sound signal arrives at a listener with a time delay from different directions, the sound signal arriving first determines the direction perceived by the listener. The direction of the sound signal arriving at the listener first is then also assigned to the sound signals arriving at the listener with a delay.
The precedence effect between the additional sound instance and the original direct sound now causes the direct sound to be localized in the direction of the virtual source. Depending on the playback signal, playback situation and structure of the real source, further manipulation of the complex frequency response and/or the localization masking level LM of the additional sound instance(s) may be necessary.
In such a manipulation of the complex frequency response, for example, subjective user settings and/or room acoustic measurements, model simulations or estimates and/or psychoacoustic measurements, model simulations or estimates and/or electroacoustic measurements, model simulations or estimates can be taken into account.
A user can, for example, select the size of the localization masking level LM or an effective frequency range according to his/her own taste.
Electroacoustic measurements, model simulations or estimates relate to predictions about the expected transmission behavior of the real source, which is to be regarded as part of the transmission path.
Room acoustic measurements, model simulations or estimates relate to predictions about the effect of the room using models or estimates. For example, a prediction of an expected transmission behavior of the room can be generated by specifying a room size, position of the real source and user, and the reflection properties of the sound-reflecting boundaries such as walls, as well as an absorption level or a scattering behavior. This knowledge can be used to determine an optimal complex frequency response or an optimum localization masking level LM.
Psychoacoustic measurements, model simulations or estimates relate to predictions in relation to a human localization in response to known ear signals. If, for example, the signals on a user's ears are known through measurements, use of models of the behavior of the real source and/or space or the like, a prediction can be generated as to whether a desired location can be reached or not. In this way, the effects of different manipulations can also be tested and an optimum determined in this way, for example. Measurements are understood here as perception experiments or listening tests with which the localization or localization-determining threshold are examined under the influence of defined ear signals.
The localization masking level LM or the amplitude of an additional sound instance can be smaller than, equal to or greater than the level L of the associated real source. For example, the first location masking level LM1 may be smaller than, equal to, or greater than the first level L1 of the real source.
Projected sound transmission paths are used to emit an additional sound instance from the direction of the reflections.
In accordance with the aforedescribed physical relationships, this radiation generates an associated additional direct sound, which can determine the localization in the same way as the original direct sound. This is the case when the additional direct sound still exceeds a location-determining auditory perceptibility threshold. In this case, the additional direct sound can be localized by newly generating a corresponding further additional sound instance from the direction of a reflection. If the resulting further additional direct sound continues to determine the auditory direction perception of the listener, the procedure can be further continued in the same way.
As a result, n localization masking levels (with LMn and ΔtMn) are cascaded until earliest additional direct sound arriving at the listener no longer exceeds the localization-determining auditory perceptibility threshold, thus making a localization in the direction of the real source impossible. In a special case of this type of cascading, all additional sound instances are preceding in time.
The localization-determining influence of direct sound can be assessed, for example, based on so-called psychoacoustic models.
Depending on the temporal and spectral characteristics of the for example several additional sound instances, the temporal and spectral characteristics of the sound of the virtual source S0 10 can be additionally manipulated. For example, this can optionally be performed using envelope manipulation or HRTF filtering.
The aforedescribed features and advantages of the present invention can be better understood and evaluated after careful study of the following detailed description of the preferred, non-limiting exemplary embodiments of the invention in conjunction with the accompanying drawings, which show in:
After a characterization or calibration of the playback situation in a specific area, such as a room 6, in which the sound-projecting audio playback system is arranged, the parameters L(f); Δt; ϑ; φ were determined for each of the direct and projected transmission channels. Here, a direct transmission channel refers to a path 8 of a direct sound from the real source S1 1 and a projected transmission channel refers to a path 9 of an indirect sound from the virtual source S0 10. Here, L(f) indicates the complex frequency response, Δt the delay time, ϑ and φ the elevation and azimuth angles in the spherical coordinate system, which is used to describe a transmission direction of the respective sound bundle of the real source into the room.
Subsequently, the localization-determining influence of direct sound is determined in a processor, such as a localization masking processor, for each playback signal x(t) having the desired localization direction ϑLok; φLok, and based thereon the number and properties of the sound bundles or beams with corresponding additionally generated sound instances 13, 13a, 13b, . . . , 13n required for playback with localization masking. Thereafter, the required control signal y(t) and the required radiation direction ϑBeam; φBeam are calculated for each sound bundle and forwarded to the sound projecting audio playback system for playback.
Such a localization masking processor refers to an arrangement suitable for data processing, which can be controlled with the present method for influencing an auditory direction perception of a listener. Such control is advantageously performed with a program that implements the method for influencing an auditory direction perception of a listener.
It is envisioned that the localization masking processor has an input for parameters L(f), Δt, ϑ, φ for each direct and each projected transmission channel. In addition, the localization masking processor has a second input for a playback signal x(t) with a desired localization direction ϑLok; φLok.
The localization masking processor also has an output for outputting control signals y(t) and their radiation direction ϑBeam; φBeam for each sound bundle. This output is connected to the real source (1) of the sound-projecting audio playback system for controlling this real source (1), such as an array of loudspeakers.
The real source S1 1 is arranged in a space 6 shown by a dash-dash line. A receiver 7 is arranged in this room, for example at the indicated position.
According to this schematic approach, a virtual source S0 10 is generated with the aid of reflections on the walls 11 of the room 6 and by a projection of the sound which is emitted by the real source S1 1 in the direction of the main lobe 4. In the illustrated example, this sound reaches the listener 7 after two reflections on the walls 11. The path of the reflected sound 9 causes a virtual source S0 10 to be generated, which the listener perceives in the example from the right rear.
In the example, the direct sound from the real source S1 1 reaches the listener via path 8. This sound, which is emitted directly from the direction of the real source S1 1 originates from an area with focus-related amplitude attenuation in the area of the side lobes 5. Since this sound has at most the intensity of a side lobe 5 of the radiation pattern 3 and is thus perceived by the listener 7 weaker than the sound via the path 9, a resulting hearing event direction 12 is produced for the listener 7 in the direction of the virtual source S0 10.
The illustrated exemplary radiation pattern 3 of the real source S1 1 is valid for a medium frequency range. As stated above, the resulting hearing event direction 12 of the listener 7 shown in
As can be seen, the sound from the real source S1 1 arrives at the listener 7 via the path 8 of direct sound, not shown in
The sound of the virtual source S0 10, which arrives at the listener 7 via the path 9 of the reflected sound, which is not shown in
The sound of the virtual source S0 10 has a level L0 or an amplitude which is greater by the difference ΔL. The reason for this greater level L0 or amplitude is the directivity or radiation pattern 3, with which the sound of the virtual source S0 10 propagating via the path 9 to the listener 7 is radiated in the area of the main lobe 5 of the real source S1 1.
In this example, a resulting hearing event direction 12 in the direction of the real source S1 1 arises, as shown on the right-hand side of
As can be seen, the additionally generated sound instance 13 is provided in such a way that it arrives at the listener 7 earlier than the direct sound component 15 of the real source S1 1 by a time difference of ΔtM1.
In a particular embodiment, the additionally generated sound instance 13 can be provided in such a way that it arrives at the listener 7 at the same time as the direct sound component 15 of the real source S1 1. In this case, too, localization masking is possible by designing the additionally generated sound instance 13 so that signal features of the direct sound component 15 are augmented so as to make localization in its direction more difficult or prevent it altogether. This can for example prevent transients by way of additional signal components, or can ambiguate localization by phase smearing.
In a further particular embodiment, the additionally generated sound instance 13 may be provided in such a way that it arrives at the listener 7 with a time delay, i.e. later than the direct sound component 15 of the real source S1 1.
The localization masking level LM1 or the amplitude of the additionally generated sound instance 13 can, as shown in
Localization masking of the direct sound component 15 of the real source S1 1 is achieved by ideally adding an additionally generated sound instance 13. This generates a resulting hearing event direction 12 in the direction of the virtual source S0 10, as shown on the right-hand side of
Due to the imperfect focusing power of the real sources S1 1, caused by the non-ideal radiation pattern 3, an additional direct sound component 14 arises in the region of the side lobes 5, which reaches the listener 7 from the direction of the real source S1 1. This undesired additional direct sound component 14 transmitted directly to the listener 7 via the path 8 is shown in the left-hand side of
The resulting hearing event direction 12 can be sufficiently influenced in this way for certain applications. There is an undesirable influence on the resulting hearing event direction 12 if the level or the amplitude of the undesired additional direct sound component 14 reaches or exceeds a localization-determining auditory perceptibility threshold for the listener 7. As shown in the right-hand side of
This drawback of the undesired additional direct sound component 14, which undesirably influences the perception of the listener 7 in the direction of the real source S1 1, is eliminated by a further measure according to the invention.
For this purpose, the additional direct sound component 14 is localization-masked by newly providing a corresponding further additionally generated sound instance 13a, which impinges on the listener 7 from the direction of the virtual source S0 10. This provision of a further additionally generated sound instance 13a is shown in
The further additionally generated sound instance 13a is provided such that it arrives with a time difference ΔtMn before the additional direct sound component 14 in order to localization-mask the additional direct sound component 14. In the example in
If the further additional direct sound component 14a generated by the further additional sound instance 13a, which reaches the listener 7 from the direction of the real source S1 1, still determines the auditory direction perception of the listener 7, the process can be further continued in the same way. Additionally generated, temporally preceding sound instances 13, 13a, 13b, . . . , 13n are cascaded until the listener 7 experiences a resultant hearing event 12 from the direction of the virtual source S0 10. This situation created by the method is shown in the right-hand side of
This situation is achieved when, after cascading n localization masking levels (with LMn and ΔtMn), the additional direct sound component 14n arriving first at the listener 7 does no longer exceed the auditory perceptibility threshold of the listener 7 that determines the localization, thereby eliminating localization in the direction the real source S1 1. The example of
Even if the signal of the additionally generated sound instance 13 shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2018 108 852.3 | Apr 2018 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2019/100214 | 3/12/2019 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2019/196975 | 10/17/2019 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 9674609 | Katayama et al. | Jun 2017 | B2 |
| 20170053641 | Kamdar et al. | Feb 2017 | A1 |
| 20170070837 | De Poortere | Mar 2017 | A1 |
| Number | Date | Country |
|---|---|---|
| 2 596 649 | Sep 2015 | EP |
| 3 142 384 | Mar 2017 | EP |
| Entry |
|---|
| International Search Report issued by the European Patent Office in International Application PCT/DE2019/100214, dated Jun. 17, 2019. |
| Hagen Wierstorf et al. “Die Rolle des Präzedenzeffektes bei der Wahrnshmung von räumlichen Aliasingartefakten bei der Wellendfeldsynthese” Fortschritte der Akustik [DAGA 2010] vol. 2, Jan. 1, 2010, pp. 639-640. |
| Cox et al. “Practical Supergain” In: IEEE Transactions on Acoustics, Speech, and Signal Processing, vol. aasp-34, No. 3, Jun. 1986. |
| Gálvez et al. “A superdriective array of phase shift sources” J. Acoust. Soc. Am., vol. 132, No. 2, Aug. 2012, p. 746-756. |
| Wühle, T .et al.: Evaluation of auditory events with projected sound sources using perceptual attributes. In: Audio Engineering Society 142nd Convention, 2017. |
| Wühle, T.; Altinsoy, M.: Investigation of auditory events with projected sound sources. In: 173rd Meeting of Acoustical Society of America and 8th Forum Acusticum, 2017. |
| Klepper, D.; Steele, D.: Constant Directional Characteristics from a Line Source Array. In: Journal of the Audio Engineering Society 11 (1963), July, No. 3, pp. 198-202. |
| Möser, M.: Amplituden-und Phasen-gesteuerte akustische Sendezeilen mit gleichmäßiger Horizontal-Richtwirkung. In: Acustica 60 (1986), April, No. 2, pp. 91-104. |
| Van der Val, M.et al.: Design of Logarithmically Spaced Constant Directivity Transducer Arrays. In: Journal of the Audio Engineering Society 44 (1996), June, No. 6, pp. 497-507. |
| Van Beuningen, G.; Start, E.: Optimizing Directivity Properties of DSP controlled Loudspeaker Arrays. In: Reproduced Sound 16 Conference, Statford (UK), 2000. |
| Keele Jr., D.: The Application of Broadband Constant Beamwidth Transducer (CBT) Theory to Loudspeaker Arrays. In: Audio Engineering Society Convention 109, 2000. |
| Keele Jr., D.: Implementation of Straight-Line and Flat-Panel Constant Beamwidth Transducer (CBT) Loudspeaker Arrays using Signal Delays. In: Audio Engineering Society Convention 113, 2002. |
| Mabande, E.; Kellermann, W.: Towards Superdirective Beamforming with Loudspeaker Arrays. In: Conf. Rec. International Congress on Acoustics, 2007. |
| Ziemer T.: “A Psychoacoustic Approach to Wave field Synthesis”, Institute of Musicology, University of Hamburg, Germany In: AES Conference 42nd International Conference: Semantic Audio Jul. 22, 2011. |
| Van der Wal, M. et al.: “Design of Logarithmically Spaced Constant-Directivity Transducer Arrays”, In: Journal of the Audio Engineering Society 44 (1996), Jun., No. 6, pp. 497-507. |
| Gálvez et al. “A superdirective array of phase shift sources” J. Acoust. Soc. Am., vol. 132, No. 2, Aug. 2012, p. 746-756. |
| Number | Date | Country | |
|---|---|---|---|
| 20210112360 A1 | Apr 2021 | US |
