ADJUSTABLE QUIET SEAT

Abstract: A noise reduction system in a personal seat comprising in combination a noise reduction system in a personal seat, the seat comprising in combination a loudspeaker and microphone mounted in a fixed positional relationship adjacent to the ear of a user, the combination being adjustable relative to the user's ear. The loudspeaker and microphone may be mounted in respective wings of the seat headrest.

Description: ADJUSTABLE QUIET SEAT This invention relates to a noise reduction system for a personal seat, including reclining seats, bunks and the like. As shown in International patent application WO89/11841, it is known to incorporate a noise reduction or attenuation system in the form of a loudspeaker and microphone combination attached to a personal seat adjacent to each ear of a person using the seat. A controller controls energisation of the loudspeaker in accordance with the sound picked up by the microphone so as to cancel noise in the region of the microphone and, thus, the user's ear adjacent to the microphone. In order to bring the noise cancellation zone as near as possible to the user's ear, the microphone is mounted at the end of a telescoping/flexible arm. However, these arms are unsightly, inhibit free movement of the user, and can even be a hazard. According to one aspect of the present invention, a noise reduction system in a personal seat comprises in combination a loudspeaker and microphone mounted in a fixed positional relationship adjacent to the ear of a user, the combination being adjustable relative to the user's ear. For convenience, the loudspeaker and microphone are adjustably mounted in the body of the seat, preferably in the headrest thereof. For improved noise attenuation, the system includes two loudspeaker/microphone combinations on respective alternate sides of the seat, adjacent to each respective ear of the user. In order that the user can optimise the noise attenuation effect of the system for his selected adjustment of the moveable portion of the seat back or headrest, the system preferably includes a gain control that is readily accessible to the user when seated. The system includes a controller for receiving the sound signals from the microphone and for transmitting a sound attenuating signal through the amplifier to the loudspeaker, the controller also including means for identifying the noise signal to be attenuated and for generating an appropriate interference signal for attenuation of the noise signal. The invention therefore provides a noise reduction or attenuation system that is compact and convenient for the user to operate, that accommodates different user heights, head sizes and head positions, and that accommodates the user's preference as to the extent to which the adjustable portions of the seat enclose the user's head. The greater the degree of enclosure of the head, the greater the noise reduction that can be achieved, but the more restricted the user's head will be. On the other hand, the further the moveable portions are spaced away from the head, the more the gain of the controller has to be increased in order to increase the attenuation zone. However, the performance is not likely to be as good as when the head is more enclosed. The spatially-fixed relationship of the loudspeaker and microphone relative to each other means that the system's response is stable once the position of the combination relative to the user's head has been set up, optimum acoustic performance being achieved at that position by adjustment of the gain control. Optionally, video or audio entertainment sound signals can be input to the system, to be emitted by the loudspeaker as a user-audible noise in addition to the noise-reduction signal which attenuates only other external noises. Optionally, an automatic gain control feature can be employed to adjust the gain without the need for user control. In that circumstance, the gain would be adjusted automatically to as high a level as possible with a reasonable stability margin. Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows conceptually the general arrangerhent; Figure 2 shows the incorporation of the system components in a seat headrest; Figure 3 shows in plan view a headrest with pivotable wings incorporating the system components; Figure 4 shows a seat including a vertically-slidable headrest; Figure 5 shows a circuit for the controller gain adjustment; and Figure 6 shows another circuit including filters for introduction of an audible entertainment signal. With reference firstly to Figure 1, the head of the user is shown at 11 and, spaced from the left ear, are mounted a microphone 12 and a loudspeaker 13. As shown in more detail with reference to Figures 2A and 2B, which show respective front and side views of a headrest 14, the microphone and loudspeaker have a fixed spatial relationship to each other, the headrest as a whole being adjustable to vary the position with respect to the head of the user. Various adjustment systems may be utilised, as more particularly described by way of example with reference to Figures 3 and 4. As shown in Figure 3, the system components are incorporated in respective wings 31,32 each pivoted about a vertical pivot axis 33,34 to the central portion 35 of the headrest which supports the rear of the user's head. As shown, the wings can be independently adjusted between a position in which they are in alignment with the central portion 35, as shown in dotted outline for wing 31, and the position at right angles thereto. In Figure 4, the seat has a seat base 41 and a seat back 42 to which is attached, via a track and slide arrangement 43, a headrest 44. The headrest can incorporate wings as shown in Figure 3. Electrical cables or other links could be incorporated or contained in the tracks. With reference to Figure 5, the gain adjustment circuit links the microphone 51 to the loudspeaker 52 via an actuator compensation- circuit 54, a gain circuit 53 and a feedback compensation circuit 55. The actuator compensation circuit filters the signal it receives to compensate for the characteristic of the loudspeaker or actuator. When this compensation circuit 54 is set so that, in the absence of circuit 55 and with 53 disconnected, the output of 51 is at the same level as the input to 54, the gain circuit is normally a negative gain which would normally be in the range from minus 0.5 to minus 10. The gain circuit may include a low-pass filter or other filter to focus the noise attenuation on one part of the frequency response. With a gain of minus 1.0, the attenuation would be greatest at the microphone. As the gain is increased, the size of the attenuation region will also increase. The feedback compensation circuit removes the effect of the loudspeaker output on the signal received from the microphone. If it is desired to add an audible entertainment signal to the attenuation signal, the entertainment signal could be fed in at 56. However, a preferable arrangement is shown in Figure 6 where the entertainment signal is introduced via filters 57 and 58. These filters are typically arranged so that the sum of the microphone signal (in response to the entertainment signal) and the output of filter 57 is as small as possible. Preferably, one or more of the circuits or filters 53,54,55,57,58 are made adaptive in response to changes in the system responses or the spectrum of the external noise to be reduced with the aim of improving the noise reduction performance of the system whilst maintaining its good performance to the entertainment signal. There are various rearrangements of Figure 6 that can be made by, for example, combining or splitting filters, but they have essentially the same effect.

Claims: Claims 1. A noise reduction system in a personal seat, the seat comprising in combination a loudspeaker and microphone mounted in a fixed positional relationship adjacent to the ear of a user, the combination being adjustable relative to the seat. 2. A noise reduction system according to claim 1, in which the loudspeaker and microphone are adjustably mounted in a body portion of the seat. 3. A noise reduction system according to claim 2 in which the loudspeaker and microphone are adjustably mounted in a headrest of the seat. 4. A noise reduction system according to any preceding claim, in which the system includes two loudspeaker/microphone combinations on respective alternate sides of the seat, adjacent to each respective ear of the user. 5. A noise reduction system according to any preceding claim in which the system includes a gain control that is readily accessible to the user when seated. 6. A noise reduction system according to any preceding claim, in which the system includes a controller for receiving the sound signals from the microphone and for transmitting a sound attenuating signal through the amplifier to the loudspeaker, the controller also including means for identifying the noise signal to be attenuated and for generating an appropriate interference signal for attenuation of the noise signal. 7. A noise reduction system according to any preceding claim, the system further including means for inputting video or audio entertainment sound signals and means for emitting said signals by the loudspeaker as a user-audible noise in addition to the noise-reduction signal which attenuates only other external noises. 8. A noise reduction system according to claim 7, including an automatic gain control means to maximise attenuation at the expected user's head position whilst maintaining a reasonable stability margin. 9. A noise reduction system according to any preceding claim and including a gain adjustment circuit linking the microphone to the loudspeaker via an actuator compensation circuit, a gain circuit and a feedback compensation circuit, the actuator compensation circuit filtering the signal it receives to compensate for the characteristic of the loudspeaker or actuator. 10. A noise reduction system according to claim 9, in which the gain circuit includes a low-pass filter or other filter to focus the noise attenuation on a required part of the frequency response. 11. A noise reduction system according to claim 10, including an entertainment signal introduced via filters arranged so that the filtered microphone signal response to the entertainment signal is as small as possible. 12. A noise reduction system according to claim 11 , in which one or more of the circuits or filters are made adaptive in response to changes in the system responses or the spectrum of the external noise to be reduced, whereby the noise reduction performance of the system is improved whilst maintaining its good performance to the entertainment signal.

Inventors: ROSS COLIN FRASER, ROSS, COLIN, FRASER
Applicants: ROSS COLIN FRASER, ULTRA ELECTRONICS LTD, ROSS, COLIN, FRASER, ULTRA ELECTRONICS LIMITED
Application year: 1999
Main classification: G10K11
IPC codes: G10K11