Abstract: An apparatus for modifying acoustic transmission comprises an array of structures arranged along a transmission path and each structure having a major axis and a minor axis, the structures being arranged such that a minor axis of each void or structure is aligned with the transmission path.

Abstract: A sound reproduction system for reproducing an audio signal as originating from a first direction relative to a nominal position (211) and orientation of a listener is provided. The system comprises a first sound transducer arrangement (105) arranged to generate sound reaching the nominal position (211) from a first position corresponding to the first direction; and a second sound transducer arrangement (107) arranged to generate sound reaching the nominal position (211) from a second position corresponding to a different direction than the first direction. The arrangements may specifically be loudspeakers positioned at the given positions. A drive circuit (103) generates a first drive signal for the first sound transducer arrangement (105) and a second drive signal for the second sound transducer arrangement (107) from the audio signal. The first position and the second position are located on a sound cone of confusion for the nominal position (211) and the nominal direction.

Abstract: A parametric loudspeaker system comprises a pre-compensator (305) for generating a pre-compensated envelope signal by applying a pre-compensation to the input audio signal where the pre-compensation compensates for distortion of in-air demodulation of the modulated ultrasound signal. A pre-modulator (307) generates a complex base band signal generating a phase signal from the pre-compensated envelope signal using a predetermined function for determining a phase signal from an amplitude signal such that the corresponding complex signal has either suppressed negative or positive frequencies. The complex base band signal is then generated to have an amplitude corresponding to the pre-compensated envelope signal and a phase corresponding to the phase signal. A modulator (309) quadrature modulates the complex base band signal on an ultrasonic quadrature carrier and an output circuit (311) drives the ultrasound transducer (301) from the modulated signal.

Abstract: A speaker system includes a first speaker (203) and a second speaker (205). A driving circuit receives an audio signal and has a first drive circuit (209) generating a first drive signal for the first speaker (203) in response to a first filtering of the audio signal with a first passband. A second drive circuit (211) generates a second drive signal for the second speaker (205) in response to a second filtering having a second passband which includes a frequency band below the first passband. A delay (213) delays the second drive signal relative to the first drive signal. The sound from the second speaker is directionally radiated with a directional radiation pattern having a notch towards the listening position (111). The system uses the precedence effect and non-direct low frequency audio radiation to ensure that directional cues are predominantly provided by the first speaker (203) which may be small and positioned remote from the second speaker (205).

Abstract: A surround sound system comprises a receiver (301) for receiving a multichannel spatial signal that comprises at least one surround channel. A directional ultrasound transducer (305) is used for emitting ultrasound towards a surface to reach a listening position (111) via a reflection of the surface. The ultrasound signal may specifically reach the listening position from the side, above or behind of a nominal listener. A first drive unit (303) generates a drive signal for the directional ultrasound transducer (301) from the surround channel. The use of an ultrasound transducer for providing the surround sound signal provides an improved spatial experience while allowing the speaker to be located e.g. to the front of the user. In particular, an ultrasound beam is much narrower and well defined than conventional audio beams and can accordingly better be directed to provide the desired reflections. In some scenarios, the ultrasound transducer (305) may be supplemented by an audio range loudspeaker (309).

Abstract: An apparatus comprises a test signal generator (401) which generates an ultrasonic test signal by modulating an audio band test signal on an ultrasonic signal. The ultrasonic test signal is radiated from a parametric loudspeaker (403) and is demodulated by non-linearities in the air. A reflected audio signal may arise from reflections of an object, such as a wall. An audio band sensor (405) generates an audio band captured signal which comprises the demodulated reflected audio band signal. A distance circuit (407) then generates a distance estimate for the distance from the parametric loudspeaker (403) to the object in response to a comparison of the audio band captured signal and the audio band test signal. Specifically two signals may be correlated to determine a delay corresponding to the full path length. Based on the distance estimates an audio environment may be estimated and a sound system may be adapted accordingly.

Abstract: A parametric loudspeaker system comprises a pre-compensator (305) for generating a pre-compensated envelope signal by applying a pre-compensation to the input audio signal where the pre-compensation compensates for distortion of in-air demodulation of the modulated ultrasound signal. A pre-modulator (307) generates a complex base band signal generating a phase signal from the pre-compensated envelope signal using a predetermined function for determining a phase signal from an amplitude signal such that the corresponding complex signal has either suppressed negative or positive frequencies. The complex base band signal is then generated to have an amplitude corresponding to the pre-compensated envelope signal and a phase corresponding to the phase signal. A modulator (309) quadrature modulates the complex base band signal on an ultrasonic quadrature carrier and an output circuit (311) drives the ultrasound transducer (301) from the modulated signal.

Abstract: A sound reproduction system for reproducing an audio signal as originating from a first direction relative to a nominal position (211) and orientation of a listener is provided. The system comprises a first sound transducer arrangement (105) arranged to generate sound reaching the nominal position (211) from a first position corresponding to the first direction; and a second sound transducer arrangement (107) arranged to generate sound reaching the nominal position (211) from a second position corresponding to a different direction than the first direction. The arrangements may specifically be loudspeakers positioned at the given positions. A drive circuit (103) generates a first drive signal for the first sound transducer arrangement (105) and a second drive signal for the second sound transducer arrangement (107) from the audio signal. The first position and the second position are located on a sound cone of confusion for the nominal position (211) and the nominal direction.

Abstract: An apparatus comprises a test signal generator (401) which generates an ultrasonic test signal by modulating an audio band test signal on an ultrasonic signal. The ultrasonic test signal is radiated from a parametric loudspeaker (403) and is demodulated by non-linearities in the air. A reflected audio signal may arise from reflections of an object, such as a wall. An audio band sensor (405) generates an audio band captured signal which comprises the demodulated reflected audio band signal. A distance circuit (407) then generates a distance estimate for the distance from the parametric loudspeaker (403) to the object in response to a comparison of the audio band captured signal and the audio band test signal. Specifically two signals may be correlated to determine a delay corresponding to the full path length. Based on the distance estimates an audio environment may be estimated and a sound system may be adapted accordingly.

Abstract: A speaker system comprises a first speaker (203) and a second speaker (205). A driving circuit receives an audio signal and comprises a first drive circuit (209) generating a first drive signal for the first speaker (203) in response to a first filtering of the audio signal with a first pass band. A second drive circuit (211) generates a second drive signal for the second speaker (205) in response to a second filtering having a second pass band which comprises a frequency band below the first pass band. A delay (213) delays the second drive signal relative to the first drive signal. The sound from the second speaker is directionally radiated with a directional radiation pattern having a notch towards the listening position (111). The system uses the precedence effect and non-direct low frequency audio radiation to ensure that directional cues are predominantly provided by the first speaker (203) which may be small and positioned remote from the second speaker (205).

Abstract: A surround sound system comprises a receiver (301) for receiving a multichannel spatial signal that comprises at least one surround channel. A directional ultrasound transducer (305) is used for emitting ultrasound towards a surface to reach a listening position (111) via a reflection of the surface. The ultrasound signal may specifically reach the listening position from the side, above or behind of a nominal listener. A first drive unit (303) generates a drive signal for the directional ultrasound transducer (301) from the surround channel. The use of an ultrasound transducer for providing the surround sound signal provides an improved spatial experience while allowing the speaker to be located e.g. to the front of the user. In particular, an ultrasound beam is much narrower and well defined than conventional audio beams and can accordingly better be directed to provide the desired reflections. In some scenarios, the ultrasound transducer (305) may be supplemented by an audio range loudspeaker (309).