Back to results
US 6,650,758 B1Granted
Adaptive dual port loudspeaker implementation for reducing lateral transmission
AssigneeNortel Networks Limited
InventorAndre J. Van Schyndel
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeNortel Networks Limited
InventorAndre J. Van Schyndel
Estimating the term…
This invention describes a loudspeaker implementation which can adaptively reduce the transmission of an acoustic signal to listeners other than the intended listener. The invention uses a dipole loudspeaker implementation with two acoustic sources, each of which is driven by a separate signal. By introducing a predetermined phase difference between the signals produced by the two acoustic sources, the null in the standard dipole spatial directivity pattern may be moved to any desired direction. Alternatively, using a microphone close to the unintended listener's ears and a suitable feedback arrangement, the null can adaptively be aligned with the direction of minimum desired sound transmission. This invention, therefore, provides a solution for applications where it is preferable to reduce the transmission of sound in particular directions while providing the listener with headphoneless audio. In particular, the invention would be effective in applications which involve embedding the implementation into a headrest, seat or other object where the direction of minimum desired transmission is known. Since the invention only involves the use of presently available components, its implementation will not add much cost to an overall system.
A directional sound source comprising a dipole loudspeaker having two acoustic sources driven by two respective electrical drivers, an audio input connected to feed an audio signal to the two electrical drivers, a null direction control means connected to the audio input to introduce a phase difference into the audio signal fed to one of the two electrical drivers relative to the other of the two electrical drivers, a microphone for sensing acoustic signals from the dipole loudspeaker and locatable in a plane in which it is desired that acoustic signals at all audible frequencies from the dipole loudspeaker be minimum such that the sound is substantially inaudible and a feedback circuit interconnecting the microphone with the null direction control means such that the null direction control means adaptively introduces the phase difference until the acoustic signals at all audible frequencies sensed by the microphone are minimum.
A null direction control module for connection to an audio input of a dipole loudspeaker having two acoustic sources driven by two respective electrical drivers, wherein the null direction control module is arranged to introduce a phase difference into the audio signal fed to one of the electrical drivers relative to the audio signal fed to the other of the electrical drivers thereby to vary the direction of a null plane of the dipole loudspeaker further comprising a null direction control means having outputs connectable respectively to the two electrical drivers, an input connected to the audio input and a further input connected to one end of a feedback circuit the other end of which is connected to an output by a microphone locatable in a desired null plane such that the null direction control means adaptively introduces the phase difference until acoustic signals at all audible frequencies sensed by the microphone are minimum.
A directional sound source comprising a dipole loudspeaker having two acoustic sources driven by two respective electrical drivers, an audio input connected to feed an audio signal to the two electrical drivers, a null direction control means connected to the audio input to introduce a phase difference into the audio signal fed to one of the two electrical drivers relative to the other of the two electrical drivers, a microphone for sensing acoustic signals from the dipole loudspeaker and locatable in a plane in which it is desired that acoustic signals from the dipole loudspeaker be minimum and a feedback circuit interconnecting the microphone with the null direction control means such that the null direction control means adaptively introduces the phase difference until the acoustic signals sensed by the microphone are minimum.
A null direction control module for connection to an audio input of a dipole loudspeaker having two acoustic sources driven by two respective electrical drivers, wherein the null direction control module is arranged to introduce a phase difference into the audio signal fed to one of the electrical drivers relative to the audio signal fed to the ocher of the electrical drivers thereby to vary the direction of a null plane of the dipole loudspeaker further comprising a null direction control means having outputs connectable respectively to the two electrical drivers, an input connected to the audio input and a further input connected to one end of a feedback circuit the other end of which is connected to an output by a microphone locatable in a desired null plane such that the null direction control means adaptively introduces the phase difference until acoustic signals sensed by the microphone are minimum.
Dependencies are inferred from the claim text.