According to one embodiment, a noise reduction apparatus includes a speaker, a generator and a controller. The speaker outputs control sound. The generator generates self-excited sound. The controller controls a phase and an amplitude of the control sound to reduce noise generated from a noise source, based on the control sound and the self-excited sound that is synchronized with the control sound.

A vehicle exhaust system includes a first exhaust gas path and a second exhaust gas path. At least one valve is positioned within the first exhaust gas path and an active noise control system is associated with the second exhaust gas path. An example method includes, providing the first exhaust gas path with a first tailpipe having a first outlet and the second exhaust gas path with a second tailpipe having a second outlet separate from the first outlet. The valve and the active noise control system are controlled simultaneously to control noise generated by the vehicle exhaust system.

A feedback noise reduction method, a feedback noise reduction system, and an earphone are provided. In the method, a channel morphological parameter of an acoustic channel between a microphone and a speaker in a feedback noise reduction system is detected; the feedback noise reduction system is switched from using a first noise reduction filter to using a second noise reduction filter in a case that it is determined that the acoustic channel is in an interfered state based on the channel morphological parameter; and a noise reduction signal is generated by using the second noise reduction filter to cancel a noise signal received by the feedback noise reduction system. A frequency response of the second noise reduction filter in a predetermined frequency band is less than a frequency response of the first noise reduction filter in the predetermined frequency band.

An unmanned flying object, capable of suppressing an increase in overall size while having a configuration to reduce noise, is provided. The unmanned flying object includes a duct that corresponds to: at least one generator that generates airflow; at least one microphone; and at least one speaker. The duct covers the at least one generator in a direction perpendicular to an airflow direction, passes the airflow in the airflow direction, includes a space between inner and outer peripheral surfaces, and defines an opening at the end of the space in the airflow direction. A shape of the inner peripheral surface is tapered in the airflow direction. The at least one microphone is positioned in the space. The at least one speaker is positioned closer to the at least one generator than the at least one microphone.

An acoustic measurement system for an industrial process asset includes a process measurement device providing a value representative of an acoustic signal near the industrial process asset based in part on a signal from an acoustic sensor positioned near the industrial process asset. A second acoustic sensor provides an acoustic value and a noise reduction component uses the acoustic value from the second acoustic sensor to affect the value provided by the process measurement device so that the value provided by the process measurement device is more representative of an acoustic signal generated by the industrial process asset.

A noise control system for a ducted rotor assembly, the ducted rotor assembly including a hub, a duct, and two or more blades coupled to the hub and supported by the duct. The noise control system including a microphone configured to receive a sound input generated by the ducted rotor assembly, the microphone configured for association with the hub; a speaker unit configured to generate a cancellation noise, the speaker configured for association with the hub; and a controller operably connected to the microphone and the speaker unit, the controller configured to selectively adjust harmonics of the cancellation noise to reduce an acoustic signature of the ducted rotor assembly. In another aspect, there is provided a rotorcraft with a ducted rotor assembly in a tail portion including a noise control system. In a third aspect, there is a method of reducing an acoustic signature of a ducted rotor assembly.

The present invention is in the field of an active sound-cancellation system, an open fluid-duct comprising such an active sound-cancellation system, such as an air duct, and an active sound-cancellation computer program comprising instructions for operating such an active sound-cancellation system. The active sound-cancellation system reduces noise significantly.

An apparatus for natural ventilation of a room, with a room delimited by walls, at least one door or one window installed in one of the room walls, a ventilation passage which is fitted to the door or the window and which communicates between the outside of the room and the inside of said room in such a way as to allow natural ventilation between the outside and inside of said room, the passage having a first end opening into the room and a second end opening to the outside of said room, and a noise absorber capable of attenuating sound waves propagating in the ventilation passage, the attenuation being realized by the generation of a counter-noise which is superimposed on said sound waves or by absorbing all or part of said sound waves.

A method to suppress noise emanating from an electrical power generator including the steps of: receiving sound emanating from the electrical power generator, wherein the sound is received in a duct for cooling air having passed through the generator; analyzing the received sound and, based on the analysis, generating a sound signal which represents a destructive sound to the received sound, and broadcasting a destructive sound into the duct, wherein the destructive sound corresponds to the sound signal.

Noise abatement within a signal stream containing unwanted signal referred to as noise is performed by acquiring a digitized noise signal and using a digital processor circuit to subdivide the acquired noise signal into different frequency band segments and thereby generate a plurality of segmented noise signals. Then individually for each segmented noise signal, the processor shifts in time the segmented noise signal by an amount dependent on a selected frequency of the segmented noise signal to produce a plurality of shifted segmented noise signals. The precise time shift applied to each noise segment considers the frequency content of the segment and the system processing time. Individually for each segmented noise signal, amplitude scaling is applied. The shifted and amplitude-scaled segmented noise signals are then combined to form a composite anti-noise signal which is output into the signal stream to abate the noise through destructive interference.