Patent Application
20070140060
The present disclosure is directed to noise reduction apparatus and methods, and more particularly, to an apparatus and method for reducing noise for a moveable target.
Active noise cancellation is a method for reducing unwanted sound. Sound consists of vibrations in the air, which can be represented as a wave. If a speaker emits a sound whose wave has the same amplitude and an exact opposite polarity to the original sound, the waves cancel out and the result is no sound. A computer analyzes the waveform of the background aural or nonaural noise, then generates a similar waveform rotated 180 degrees out of phase to cancel background noise out by interference. This method differs from passive “noise cancellation” (sound proofing) such as insulation, sound-absorbing ceiling tiles, automobile mufflers or using headphones to suppress the noise. The advantages of active noise control methods compared to passive ones are: they are more effective, less bulky, and can be made to be selective, that is, to block unwanted noise (e.g. from an engine) but not useful sound (e.g. voice).
Active noise cancellation involves superimposing on a noise acoustic wave an opposite acoustic wave that destructively interferes with and cancels the noise acoustic wave. In active noise cancellation systems, the characteristics of the noise acoustic wave are sensed, a canceling acoustic wave is generated and delivered to a location through a speaker. The combined waves are monitored at the location and a feedback or error signal is produced for interactive adjustment of the cancellation of the noise acoustic wave.
Implementation of the active noise cancellation principle is arranged to accommodate changes in the frequency and intensity characteristics of the noise acoustic wave by incorporating adaptability into the feedback or error path of the active noise cancellation system.
Active noise cancellation systems generally provide only a relatively small and geographically fixed volume of “quiet space”. In a larger environment, this space would not accommodate the normal movement of an item or person within that larger space. Thus, with current technology, the quiet space is relatively small and fixed, and if the target moves outside this space, there is little or no reduction of noise.
U.S. Patent Application Publication No. US 2005/0226434, describes a noise reduction system employed in a working environment to reduce the noise that a user within that working environment experiences. The system determines the user's location within the working environment and produce a remedial noise profile that is configured to reduce the noise that the user experiences at the user's current location. The noise reduction system includes multiple speakers installed in the working environment. A signal that represents the remedial noise profile is used to drive one or more speakers proximate the user's current location so that the user experiences less noise at that location.
One disadvantage of the noise reduction system disclosed in the 2005/0226434 publication is that the system only can reduce noise by turning on the speakers proximate to the user's location when the user is relatively stationary at the location. The system cannot provide an effective noise cancellation for the user when the user is moving.
The apparatus and method for reducing noise for a moveable target of the present disclosure solves one or more of the problems set forth above.
In one aspect, the present disclosure is directed to a noise control system for controlling a noise level around a moveable target. The noise control system includes a detecting system for detecting a location and movement of the target, and a noise cancellation system. The noise cancellation system includes a sensor for dynamically sensing a noise acoustic wave at the location of the target. The noise cancellation system is configured to be responsive to a detection of the location of the target by the detecting system and the sensed noise acoustic wave by the sensor, and provide a noise cancellation wave to a first space at and around the location of the target. The noise cancellation system is further configured to be responsive to a detection of the movement of the target by the detecting system and the sensed noise acoustic wave, and provide a noise cancellation wave to a second space to cover the moving target. The second space is larger than the first space.
In another aspect, the present disclosure is directed to a method for providing reduction of a noise level for a moveable target. The method includes detecting a first location of the target and detecting a noise acoustic wave at the first location. A noise cancellation wave is provided in response to the noise acoustic wave to a first space at and around the first location of the target. A movement of the target is detected, and a noise cancellation wave is provided in response to the noise acoustic wave to a second space to cover the moving target. The second space is larger than the first space.
In one embodiment as shown in
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In one embodiment, the noise control system 10 is configured to track movement of the target 12 and use algorithms for optimization of the noise cancellation for the target 12. For example, when the target location detecting system 20 detects that the target 12 is moving, the noise cancellation system 30 can make tradeoffs in the algorithms to make the volume of the noise cancellation space larger but not as “quiet”. Upon detection that the target has stopped moving, the noise cancellation system 30 may reduce the size of the noise cancellation space, while increasing the noise cancellation quality. The implementation of such optimization is described in detail below.
In one embodiment, when the target 12 moves as determined by the target location detecting system, the noise acoustic wave received by the noise sensor 32 changes. The noise sensor 32, which generated the noise signal representative of the noise profile of a first space 42 at and around the target location, now generates a new noise signal representative of a noise profile of a second space 44 which is larger than the first space and covers the moving target. In one embodiment, the new noise signal represents the noise profile in the larger second space 44, and therefore, for the purpose of reducing the noise level around the target, the new noise signal may be not as accurate as the original noise signal which represents the noise profile in the smaller first space 42. In response to the detection of the movement of the target 12 and the new noise signal, the processor 34 adjusts the acoustic signal generator 36 to produce a new noise cancellation wave and direct the noise cancellation wave to cover the second space 44 to reduce the noise in the second space 44. In directing the acoustic signal to the second space 44, in one embodiment, the processor 34 may adjust the speaker 38 to produce sound in a wider angle. In another embodiment, in which multiple speakers are used, the processor 34 may selectively turn on more speakers to cover the larger second space 44. When the target stops moving, upon the detection of the target being stationary, the processor 34 adjusts the acoustic signal generator 36 to produce a noise cancellation wave in response to a noise profile in a third space 46 at and around the stationary target's location, which is smaller than the second space 44. The processor 34 adjusts the speaker or speakers 38 to deliver the noise cancellation wave to the third space 46 to reduce the noise in the third space 46 at and around the target 12.
The target location detecting system 20 can be any suitable means for detecting the location of the target. In one embodiment, the target location detecting system 20 may include a Global Positioning System (GPS) for detecting the location of the target 12. In another embodiment, the target location detecting system 20 includes at least one transmitter for generating signals, and at least one receiver for receiving the signals. Either the transmitter or the receiver is attached to the target 12, and the detecting system 20 is configured to determine the location of the target 12 based on the time of arrival of the signals from the transmitter to the receiver. In yet another embodiment, the detecting system 20 may include a Doppler radar system for detecting the location of the target 12. In a further embodiment, the detecting system 20 may include a triangulation system for detecting the location of the target. In yet another embodiment, the detecting system 20 may include an optical system for detecting the location of the target 12, for example, a camera. In yet another embodiment, the detecting system 20 may include a sensor attached to the target 12. The sensor could be configured to detect a change of the noise amplitude indicative of the movement of the target 12. Alternatively, the sensor may be configured to detect a change of the noise frequency indicative of the movement of the target 12.
In a further embodiment as shown in
The disclosed system for reducing'noise for a movable target may be implemented in any environment to reduce the noise that a user within that environment experiences, including a work machine cabin, a work site, etc. By implementing the disclosed system, the noise level perceived by a worker at the work site or an operator in the work machine can be reduced. The operation of the system for reducing noise for a movable target will now be explained.
Several advantages over the prior art may be associated with the noise control system. A target, for example, a worker at a work site or an operator in a vehicle or of a machine, sometimes move from one area to another during working. The prior art can only provide a fixed “quiet space”, and if the target moves outside of the “quiet space”, the target will not be protected from the noise. The disclosed system can provide a “quiet space” to cover the moving target by enlarging the “quiet space”, and reducing the “quiet space” when the target is stationary. The disclosed system, therefore, can provide an optimal noise attenuation to the moveable target.
It will be apparent to those skilled in the art that various modifications and variations can be made to the noise control system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed noise control system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
