Abstract: An active noise cancellation system includes a series of features for more effective cancellation, greater reliability, and improved stability. A particular feature adapted for headset systems includes locating a residual microphone radially offset from the center of a sound generator to detect a signal more similar to that incident upon the eardrum of the user. In addition, an open back headset design includes perforations on the side of the headset instead of the back, so that the perforations are less susceptible to inadvertent blockage. The system also includes a mechanism for detecting changes in the acoustic characteristics of the environment that may be caused, for example, by pressure exerted upon the earpieces, and that may destabilize the cancellation system. The system automatically responds to such changes, for example, by reducing the gain or the frequency response of the system to preserve stability.

Abstract: The invention relates to a controlled acoustic wave guide configured as an elongated hollow chamber (1) which via an opening (2) in its first face end (3) is connected to a sound-conducting channel (4). The longitudinal resonances of the hollow chamber (1) can be adjusted to a sound spectrum to be dampened. To this end diaphragm vibrations are detected by means of a microphone (10) which is positioned directly in front of the diaphragm (8) of at least one loud-speaker (9) at the second face-end (6) of the hollow chamber (1). The microphone signal is then inverted using an amplifier (11) and fed back to the loud-speaker (9) after amplification in accordance with a sensor (12) signal characterizing the sound spectrum in the channel (4).

Abstract: The invention refers to a device for sound control in a space (2) with a sound field from at least one sound source (3). The device includes a pulse sensor (5), which provides a pulse signal from the sound source (3). Moreover, the device includes a number of sound influencing members (8) for reducing the sound field in the space (2) and a number of sound sensors (9), which sense the actual sound field in the space and provide an error signal. A control unit includes a signal supplied device (11, 12), which receives a pulse signal and supplies a first signal to an adaptive filter (15). The filter has a number of filter coefficients and generates a drive signal for each sound influencing member (8). The signals supply device also supplies second signals to a calculating member (24), which calculates the value of the filter coefficients by the second signals and the error signals for updating the adaptive filter (15).

Abstract: An active noise control system (20) includes a controller (34) having an error signal processing module (38). The controller (34) updates a value of an adaptive filter (40) based upon an averaged error signal (56). A convergence factor (58) used in a least mean square update equation (60) can be selected independent of an averaging parameter &tgr;E, which allows for faster convergence without the otherwise associated instability.

Abstract: Some workers wear headsets to protect their hearing from loud persistent noises, such as airplane engines and construction equipment. These headsets are generally passive or active, with the active ones including ear speakers and automatic noise-reduction (ANR) circuitry to cancel or suppress certain types of loud persistent noises. One problem with active headsets, particulary those that are battery-powered, concerns battery life. Workers often take the headset off or store them without turning them off and thus wasting costly battery life. Accordingly, the inventor devised active headsets with automatic turn-on and/or turn-off circuits. One exemplary embodiment senses a condition of the headsets, for example, the light, pressure, or temperature within one earcup, and then turns the headset on or off in response to the sensed condition.

Abstract: A method and apparatus for actively influencing the intake noise of an internal combustion engine. The apparatus comprises a controller (7) which senses the actual noise (I) via a microphone (16) and compares the actual noise with a reference noise signal which depends on the engine speed D and at least one further engine parameter P, such as, for example, the throttle (12) position. A comparison signal V generated by comparing the actual noise to the reference noise value is used to adjust a control signal Asum, which also depends on the engine speed D. The control signal is fed to an electromechanical transducer (14) which generates a correcting noise (20) which is superimposed on the intake noise (21) to produce the resultant actual noise (22), which should correspond as closely as possible to the reference noise value.

Abstract: An active noise control system (100) and method compensates for changes in a microphone output to maintain accurate noise control. A calibration signal reflecting a desired microphone output is generated and stored in an active noise control module (106). During operation, the active noise control module (106) compares an actual microphone output signal with the calibration signal and compensates for any changes in the actual output signal before any noise compensation or cancellation function occurs.

Abstract: An active noise cancellation system (26) for controlling engine noise propagation through a vehicle induction system (32) is customizable to achieve a desired engine noise profile. A controller (34) of the active noise cancellation system drives a speaker (36) to generate a noise cancellation sound in a manner consistent with an individual's indicated preference for a specific type of available engine noise profile. By customizing how the speaker is driven, the system customizes the resulting engine noise heard in the passenger compartment. In one example, the system is customizable using a hand held communication device (24) such as a cell phone, a personal digital assistant or a so-called palm top computer. In another example, a resident communication bus on the vehicle is accessed through a user communication interface (28) supported on the vehicle.

Abstract: A method and apparatus for actively influencing the intake noise of an internal combustion engine. The apparatus comprises a controller (7) which senses the actual noise (I) via a microphone (16) and compares the actual noise with a reference noise signal which depends on the engine speed D and at least one further engine parameter P, such as, for example, the throttle (12) position. A comparison signal V generated by comparing the actual noise to the reference noise value is used to adjust a control signal Asum, which also depends on the engine speed D. The control signal is fed to an electromechanical transducer (14) which generates a correcting noise (20) which is superimposed on the intake noise (21) to produce the resultant actual noise (22), which should correspond as closely as possible to the reference noise value.

Abstract: Control data such as an optimal filter coefficient or the like of an engine mount is obtained by adaptation control or the like with respect to a reference vehicle F provided with a reference engine mount 20k, and the control data is stored in a reference data map storage medium 35 as a reference data map. Mount characteristics of the reference engine mount and a mass-produced engine mount 20m are measured. A correction data map which is a deviation from the reference data map is obtained for the control data of the mass-produced engine mount from a difference between both the mount characteristics, and the correction data map is stored in the correction data map storage medium 36. Both the data map storage media are added to the active control apparatus of the mass-produced vehicle M. Using both the data maps, it is possible to appropriately and actively control the vibration of the mass-produced vehicle without variation.

Abstract: The air induction system comprises an air induction body and speaker disposed about the air induction body. A control unit communicates with the speaker and has at least two modes of noise attenuation signal generation. An engine speed sensor communicates engine speed data to the control unit. An engine load sensor communicates engine load data to the control unit as well. The control unit then selects one of the at least two modes of noise attenuation based on the engine speed data and the engine load data.

Abstract: The active noise attenuation system comprises a speaker, a control unit in communication with the speaker, and a memory unit in communication with the control unit storing cancellation waveform data. The system uses the stored cancellation waveform data to create a cancellation waveform through a speaker in proximity to an air induction system to thereby attenuate engine noise. Sensors serve to trigger the release of the cancellation waveform as well as to affect the form of the cancellation waveform to ensure noise attenuation.

Abstract: A method for predicting a noise intensity emitted from a fan is provided. The method in accordance with the present invention provides data about the performance of the fan and a noise intensity corresponding to a shape of the fan and operating conditions so that the data are used in design and manufacturing of fans. The method comprises following steps for: analyzing a flow field around the fan on the basis of a fan shape and operating conditions; obtaining a noise source value of the fan from force data of blades at a given time in the analyzed flow field; and calculating a noise intensity from the noise source value.

Abstract: A noise canceler of the present invention is of the type including an adaptive filter for generating a pseudo noise signal, subtracting the pseudo noise signal from a received signal to thereby output an error signal, and sequentially correcting the filter coefficient of the filter in accordance with the error signal. A second adaptive filter produces a second pseudo noise signal and a second error signal. A first and a second power mean circuit each calculates the signal power of the respective signal. A divider performs division with the resulting two kinds of signal power, so that a signal-to-noise power ratio is estimated. A comparator compares the estimated signal-to-noise power ratio and a delayed version of the same and outputs greater one of them as an extended signal-to-noise power ratio.

Abstract: A fan noise canceller comprises a rotation information detecting means 2 (or 12) for detecting noise information of a fan 1 (11), a band-pass filter 3 (13) for extracting the blade passing frequency from the noise information, an output control means 4 (14) for controlling the amplitude and phase of the blade passing frequency signal of the extracted noise information, and a cancelling loud-speaker 2 (25) for converting the output of the output control means 4 (41) into a sound signal. The rotation information detecting mean 2 (21) Yincludes a rotatable disc 2A coupled to the shaft of the fan 1 (11) and carrying change information corresponding to the number of fan blades, and a photo-interrupter 2B for outputting signals of the blade passing frequency and harmonics thereof contained in the rotation information of the rotatable disc 2A as electric signals.