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.

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.

According to one embodiment, an estimating apparatus includes an insertion tube, a first sensor, a second sensor, a processing unit, an adder, and an analyzer. The insertion tube is detachably mounted midway along a coupling tube that couples an excitation source to a main unit. The first sensor is provided inside the insertion tube at a first distance from an exit of a space housing the excitation source. The second sensor is provided at a second distance from the first sensor. The processing unit performs filter processing to a first signal obtained by the first sensor. The adder adds a filtered signal and a second signal obtained by the second sensor, the first signal being the first signal having undergone filter processing by the processing unit. The analyzer analyzes a frequency of a signal obtained by the adder.

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.

According to one embodiment, an estimating apparatus includes an insertion tube, a first sensor, a second sensor, a processing unit, an adder, and an analyzer. The insertion tube is detachably mounted midway along a coupling tube that couples an excitation source to a main unit. The first sensor is provided inside the insertion tube at a first distance from an exit of a space housing the excitation source. The second sensor is provided at a second distance from the first sensor. The processing unit performs filter processing to a first signal obtained by the first sensor. The adder adds a filtered signal and a second signal obtained by the second sensor, the first signal being the first signal having undergone filter processing by the processing unit. The analyzer analyzes a frequency of a signal obtained by the adder.

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.

A fan control system applied to N fans inside a computer system is disclosed, comprising: a main microphone, a control circuitry, a wave generation circuitry and a number N of fan controllers. The control circuitry calculates a basic frequency value according to a temperature inside the computer system, and continuously updates a parameter by any known optimization algorithm according to a main audio signal from the main microphone. The wave generation circuitry generates N square waves according to the basic frequency value and the parameter. The N fan controllers respectively form and transmit N modulation signals to the N fans according to the N square waves and N tachometric signals from the N fans. The parameter is one of a frequency variation and a set of phase differences, and the N square waves have the same frequency.

An active duct noise control system and a method thereof are provided, including a duct, a noise source speaker, a microphone, a plurality of noise-cancelling speakers, and a plurality of controllers. Wherein, the noise source speaker generates the primary noise, and the microphone is disposed to receive the residual noise. The plurality of noise-cancelling speakers are disposed between the noise source speaker and the microphone and respectively generate noise-cancelling audio frequencies to offset the primary noise and reduce the residual noise. The plurality of controllers are respectively connected to the plurality of noise-cancelling speakers and the noise source speaker and calculate each of the noise-cancelling audio frequencies generated by each of the plurality of noise-cancelling speakers according to the multi-channel inverse filtering principle.

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 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.