Systems and methods for reducing noise or vibration generated by an internal combustion engine are described. An engine controller is arranged to operate the working chambers of the engine in a cylinder output level modulation manner. A noise/vibration reduction unit actively control of a device that is not a part of the powertrain. The device is controlled in a feed forward manner to alter an NVH characteristic of the vehicle in a desired manner based at least in part on a characteristic of the cylinder output level modulation operation of the engine.

A microphone system may include a measuring device that includes a plurality of sound elements and a semiconductor chip connected to the sound elements and receives a vibration signal and a noise signal from the outside to cancel the vibration signal and changes a phase of the noise signal to output a reverse phase noise signal; and a driver that is connected to the semiconductor chip and is included in a front glass of a vehicle and vibrates in response to the reverse phase noise signal to cancel a noise signal inputted from the outside.

An acoustic conversion device for an active noise control is provided. The acoustic conversion device can effectively suppress or remove noise by controlling variation in a lowest resonance frequency. A volume of a closed space is smaller than an equivalent compliance air volume of a speaker unit. Therefore, motion of a vibration plate, an edge and a damper is suppressed, it is possible to restrain the edge and the damper from being deteriorated with time, variation in lowest resonance frequency can be suppressed, phase of emitted sound can be less prone to be deviated from opposite phase of noise, and it is possible to effectively suppress or remove noise.

A loudspeaker device includes: a first loudspeaker that outputs a sound; a second loudspeaker that is adjacent to the first loudspeaker in a predetermined direction and outputs a sound in a direction intersecting with a direction in which the first loudspeaker outputs the sound; and a phase switching circuit that switches between a first switching state and a second switching state, the first switching state being a state in which an input sound signal is inputted to both the first loudspeaker and the second loudspeaker, the second switching state being a state in which the input sound signal is inputted to one of the first loudspeaker and the second loudspeaker while an inverted sound signal obtained by inverting a phase of the input sound signal is inputted to the other of the first loudspeaker and the second loudspeaker.

An acoustic liner may include a core with a plurality of resonator chambers, a perforated top sheet coupled to the core, and a backskin coupled to the core. A thermoacoustic speaker including nanomaterials may be coupled to at least one of the core, the backskin, and the perforated top sheet. A voltage may be applied to the thermoacoustic speaker. The thermoacoustic carbon nanotube speaker may create a dynamic excitation within a resonator chamber in the core. The dynamic excitation may change the liner acoustic impedance to achieve optimum noise attenuation over a wide range of frequencies or engine operating conditions.

A system includes an Active Noise Control (ANC) module unit configured to be installed within an air intake or exhaust of a power generation unit. The ANC module unit includes an ANC housing shaped to fit within the air intake or exhaust, an ANC core configured to be secured within the ANC housing, which includes a microphone configured to detect a sound generated by the power generation unit, a control board configured to control the noise-canceling sound based on the sound signal from the microphone and a set of pre-determined noise reduction transfer functions, and a first speaker configured to deliver a first noise-canceling sound to the air intake or exhaust.

Sound attenuation is performed using a sound attenuation panel using an electromagnetic or electrostatic response unit to modify resonance. The sound attenuation panel has an acoustically transparent planar, rigid frame divided into a plurality of individual cells configured for attenuating sound. In one configuration, each cell has a weight fixed to the membrane. The planar geometry of each said individual cell, the flexibility of the membrane, and the weight establish a base resonant frequency for sound attenuation. The electromagnetic or electrostatic response unit is configured to modify the resonant frequency of the cell.

An acoustic conversion device for an active noise control including a protection member is provided. Since the protection member hides an entire opening, all of water and foreign matters which pass through the opening arrive at an upper surface of the protection member. Further, since the protection member hides the entire speaker unit, it is possible to protect a vibration plate of the speaker unit from water and foreign matters which drop from the protection member. Therefore, water and foreign matters are prevented from adhering to the vibration plate, it is possible to prevent lowest resonance frequency from being varied, emitted sound can be less prone to be deviated from opposite phase of noise, and it is possible to effectively suppress or remove noise.

An acoustic conversion device for an active noise control is provided. The acoustic conversion device can effectively suppress or remove noise by controlling variation in a lowest resonance frequency. A volume of a closed space is smaller than an equivalent compliance air volume of a speaker unit. Therefore, motion of a vibration plate, an edge and a damper is suppressed, it is possible to restrain the edge and the damper from being deteriorated with time, variation in lowest resonance frequency can be suppressed, phase of emitted sound can be less prone to be deviated from opposite phase of noise, and it is possible to effectively suppress or remove noise.

An audio amplifier circuit may include a power amplifier, a charge pump power supply, and a control circuit. The power amplifier may have an audio input for receiving an audio input signal, an audio output for providing the output signal, and a power supply input. The charge pump power supply may provide a power supply voltage to the power supply input. The charge pump power supply may have a select input for selecting an operating mode of the power supply. In a first operating mode, the power supply voltage may equal to a first voltage, and in a second operating mode, the power supply voltage may be substantially equal to a second voltage which is a rational fraction of the first voltage. The control circuit may generate the select input based on a magnitude of anti-noise generated by an adaptive noise cancellation system associated with the audio transducer.