Abstract: A refrigerator includes a noise reduction device and a machine room that accommodates a condenser and a compressor. The noise reduction device includes a sensing unit configured to measure noise generated from the machine room of the refrigerator and a generating unit configured to output a sound signal having a frequency canceling or reducing the noise. The machine room is defined by a case that has a communication portion configured to communicate a fluid between an inside of the case and an outside of the case to thereby exchange heat between the fluid and the condenser and between the fluid and the compressor.

Abstract: Wind turbine comprising a tower (2) bearing a nacelle (5) and a rotor (3) with a plurality of rotor blades (4) and an active noise reduction device (7), wherein the active noise reduction device (7) comprises at least one actuator (8), at least one unsteady pressure sensor (9) adapted to produce an output signal corresponding to a turbulent flow condition during operation of the rotor blade (4), at least one noise sensor (10) adapted to produce an output signal corresponding to a noise generated by the rotor blade (4) at the location of the noise sensor (10), and a control unit (11), wherein the unsteady pressure sensor (9) and the actuator (8) are arranged on at least one of the rotor blades (4) and the noise sensor (10) is arranged at the nacelle (5) and/or at the tower (2), wherein the control unit (11) is adapted to control the actuator (8) in dependence of the output signals of the unsteady pressure sensor (9) and the noise sensor (10) to emit an anti-noise signal at least partly reducing the noise gener

Abstract: Provided are methods and systems for enhancing speech when corrupted by transient noise (e.g., keyboard typing noise). The methods and systems utilize a reference microphone input signal for the transient noise in a signal restoration process used for the voice part of the signal. A robust Bayesian statistical model is used to regress the voice microphone on the reference microphone, which allows for direct inference about the desired voice signal while marginalizing the unwanted power spectral values of the voice and transient noise. Also provided is a straightforward and efficient Expectation-maximization (EM) procedure for fast enhancement of the corrupted signal. The methods and systems are designed to operate easily in real-time on standard hardware, and have very low latency so that there is no irritating delay in speaker response.

Abstract: A method of operating a motor driving a rotating member includes directing rotation of the rotating member at the motor at an initial speed, determining a first frequency of a first noise component generated by the rotating member at the initial speed, determining a second noise component having a second frequency phase shifted 180° with respect to the first frequency, determining a torque modifier of the motor to generate the second noise component from the motor, and directing activation of the motor according to the determined torque modifier.

Abstract: An apparatus on a vehicle comprises one or more sensors, one or more nozzles that output fluid to clean the respective one or more sensors, and a compressor that generates fluid such as compressed air. The compressor is in fluid communication with the one or more nozzles. The apparatus further comprises one or more processors, and a memory storing instructions that, when executed by the one or more processors, cause the system to determine information of an acoustic emission from the compressor and to counteract the acoustic emission based on the determined information.

Abstract: For example, an apparatus may include an input to receive input information including a Heating, Ventilation and Air Conditioning (HVAC) input including HVAC configuration information corresponding to a configuration of an operation of an HVAC system of a vehicle; a plurality of noise inputs representing acoustic noise at a plurality of noise sensing locations; and a plurality of residual-noise inputs representing acoustic residual-noise at a plurality of residual-noise sensing locations within at least one sound control zone in the vehicle; a controller configured to determine a sound control pattern to control sound within the at least one sound control zone in the vehicle, the controller configured to determine the sound control pattern based on the HVAC input, the plurality of noise inputs and the plurality of residual-noise inputs; and an output to output the sound control pattern to a plurality of acoustic transducers.

Abstract: Audio signal processing for adaptive de-reverberation uses a least mean squares (LMS) filter that has improved convergence over conventional LMS filters, making embodiments practical for reducing the effects of reverberation for use in many portable and embedded devices, such as smartphones, tablets, laptops, and hearing aids, for applications such as speech recognition and audio communication in general. The LMS filter employs a frequency-dependent adaptive step size to speed up the convergence of the predictive filter process, requiring fewer computational steps compared to a conventional LMS filter applied to the same inputs. The improved convergence is achieved at low memory consumption cost. Controlling the updates of the prediction filter in a high non-stationary condition of the acoustic channel improves the performance under such conditions. The techniques are suitable for single or multiple channels and are applicable to microphone array processing.

Abstract: With the noise reduction device (300), in identifying an acoustic transfer function that includes a path from the control speaker (340) to the error microphone (350) or the noise microphone (320) by outputting an identification sound from the control speaker (340) and detecting the identification sound with the error microphone (350) or the noise microphone (320), the identification controller (338) is configured to identify the acoustic transfer function by generating the identification sound from the white noise generator (337) when the seat detector (582) has detected that the seat is in the actual usage state for noise reduction.

Abstract: A gas turbine engine generates noise during use, and one particularly important flight condition for noise generation is take-off. A gas turbine engine has high efficiency together with low noise, in particular from the turbine that drives the fan. The contribution of the turbine noise emanating from the rear of the engine to the Effective Perceived Noise Level (EPNL) is in the range of from 7 EPNdB and 30 EPNdB lower at a take-off lateral reference point than at an approach reference point.

Abstract: A rotor blade with a leading edge and a trailing edge, wherein the rotor blade is designed and configured for being exposed to a fluid flowing substantially from the leading edge to the trailing edge) of the rotor blade, the rotor blade includes at least one sensor for detecting flow characteristics of the fluid, and the rotor blade further includes at least one actuator for producing an anti-noise signal. The sensor and the actuator are both arranged at the surface of the rotor blade, and the actuator is arranged and prepared such that flow-induced edge noise of the rotor blade, which is generated by the fluid, is at least partly cancelled out by the anti-noise signal. The disclosure furthermore relates to a wind turbine including at least one such rotor blade.

Abstract: Active noise cancellation is employed to address unwanted acoustical noise generated by various equipment associated with an ophthalmic surgical system. Active noise cancellation may be used within a chassis of the ophthalmic surgical system, within an air compressor used with the ophthalmic surgical system, and within a reciprocating surgical probe used with the ophthalmic surgical system.

Abstract: In various embodiments, methods, systems, and vehicles are provided for masking a tonal noise of a motor. In certain embodiments, a vehicle includes a drive system and an active masking acoustic signal generator (AMAG). The drive system includes a motor generating a tonal noise. The AMAG is configured to at least facilitate masking the tonal noise, by introducing a complementary harmonic tone, injecting dithering into the motor, or both.

Abstract: Provided are a signal processing device, a program, a range hood device, and a selection method for frequency bins in a signal processing device with which it is possible to reduce the load on computation processing for computing filter coefficients and provide an excellent muting effect even when there are a peak band and a notch band in transmission characteristics from a speaker to an error microphone. A parameter setter sets an update parameter ? such that a filter coefficient W is corrected, only for a first frequency bin that corresponds to a frequency band of a first noise and a second frequency bin that corresponds to a frequency band of a second noise.

Abstract: A silencer is to be used in combination with a range hood system to suppress noise made by a fan. In a silencing circuit, a disturbance detector detects mixing of disturbance sound to a correction signal and an error signal. When the disturbance detector detects the mixing of the disturbance sound, an updating stopper causes a coefficient updater to stop a processing of updating a filter coefficient of a silencer filter, relating to, as an object, at least a frequency band other than a frequency band of the noise.

Abstract: A noise cancelation device that programs, records, and saves sounds and noises and their respective sound waves, inverts them, and broadcasts the inverted sound waves, thereby reducing, deadening, canceling, or eliminating, the original sounds and noises, and their respective sound waves. Further, the noise cancelation device can save sounds and noises that have a constant, predictable, steady, and recognizable sound quality and their respective sound waves, and preprogram the respective inverted sound waves, which allows for the noise cancelation device to broadcast the preprogrammed inverted sound waves through speakers to reduce, deaden, or cancel the original sounds and noise when they are present. The noise cancelation device is portable and may be used in any location desired, or the noise cancelation device may be is fixed in its location.

Abstract: A system and method are provided for taxonomically distinguishing grouped segments of signal data captured in unconstrained manner for a plurality of sources. The system comprises a vector unit constructing for each of the grouped signal data segments at least one vector of predetermined form. A sparse decomposition unit selectively executes in at least a training system mode a simultaneous sparse approximation upon a joint corpus of vectors for a plurality of signal segments of distinct sources. The sparse decomposition unit adaptively generates at least one sparse decomposition for each vector with respect to a representative set of decomposition atoms. A discriminant reduction unit executes during the training system mode to derive an optimal combination of atoms from the representative set. A classification unit executes in a classification system mode to discover for an input signal segment a degree of correlation relative to each of the distinct sources.

Abstract: Systems and techniques for cancelling fan noise by providing an anti-noise waveform are disclosed. In some embodiments, the systems and techniques include receiving, at a fan, a pulse width modulated signal from a power supply. A fan blade of the fan is rotated at a spin speed that is measured by a first sensor. A second sensor detects a position of the fan blade. Based on the spin speed and the position, an anti-noise waveform is generated that is configured to cause destructive interference with a fan noise of the fan. An audio signal is output that corresponds to the anti-noise waveform to cause destructive interference with noise caused by the spinning blades of the fan.

Abstract: System and method for producing enhanced speech data associated with at least one speaker. The process of producing the enhanced speech data comprises: receiving distant signal data from a distant acoustic sensor; receiving proximate signal data from a proximate acoustic sensor located closer to the speaker than the distant acoustic sensor; receiving optical data originating from an optical unit configured for optically detecting acoustic signals in an area of the speaker and outputting data associated with speech of the speaker; processing the distant and proximate signals data for producing a speech reference and a noise reference; operating an adaptive noise estimation module, which identifies stationary and/or transient noise signal components, using the noise reference; and operating a post filtering module, which uses the optical data, speech reference and identified noise signal components for creating an enhanced speech data.

Abstract: Methods, systems, and apparatuses are provided for controlling an environmental maintenance system that includes a plurality of sensors and a plurality of actuators. The operation levels of the actuators can be determined by optimizing a penalty function. As part of the penalty function, the sensor values can be compared to reference values. The optimized values of the operation levels can account for energy use of actuators at various operation levels and predicted differences of the sensor values relative to the reference values at various operation levels. The predicted difference can be determined using a transfer model. An accuracy of the transfer model can be determined by comparing predicted values to measured values. This accuracy can be used in determining new operational levels from an output of the transfer model (e.g., attenuating the output of the transfer model based on the accuracy).

Abstract: A fan active noise self-lowering system includes a fan, a push assembly, at least one pickup unit and a digital signal processing unit. The pickup unit serves to capture the noise made by the fan to generate a noise input signal and transmit the noise input signal to the digital signal processing unit. The digital signal processing unit receives the noise input signal and processes the noise input signal to output a control signal for controlling the push winding assembly to operate so as to push the fan impeller of the fan to move up and down. Accordingly, the fan impeller will generate a reverse sonic wave to offset the noise.

Abstract: Provided are a method and apparatus comprising an active noise reduction system. The active noise reduction system comprises an input transducer for transducing acoustic noise to a noise signal. The input transducer has a first sensitivity at a threshold temperature. The active noise reduction system includes circuitry that receives the noise signal and, in response, compensates for an effect by an ambient temperature on a second sensitivity of the input transducer by preventing the second sensitivity from being greater than the first sensitivity in response to a temperature deviation from the threshold temperature.

Abstract: A method for reducing the noise emission of a transformer, the transformer tank of which is filled with liquid and the tank wall of which vibrates during operation, is provided. The method is characterized by the sequence of the following method steps: detecting natural frequency values of the tank wall for at least one excitation frequency; determining at least one eigenmode for which the vibration of the tank wall is composed at an excitation frequency, from the natural frequency values, wherein areas of large curvature are determined on the tank wall; arranging at least one vibration loading device in at least one of said areas; and controlling the at least one vibration loading device by means of a control device in order to counteract the vibration of the tank wall.

Abstract: A system for controlling fan noise includes a fin, a fan, a sensor, a signal processing unit, and a speaker. The fin has a front side and a rear side opposite to the front side. The fan is disposed adjacent to the front side and has an airflow outlet, and the airflow outlet faces the front side. The sensor is disposed adjacent to the rear side and is used for receiving a sound signal made by the fan. After the signal processing unit receives the sound signal sent by the sensor, the signal processing unit provides an inversed phase signal by analysis and computation. The speaker is disposed adjacent to the rear side, for receiving and outputting the inversed phase signal provided by the signal processing unit, so as to offset the noise made by the fan.

Abstract: Provided are methods and systems for noise suppression within multiple time-frequency points of spectral representations. A multi-feature cluster tracker is used to track signal and noise sources and to predict signal versus noise dominance at each time-frequency point. Multiple features, such as binaural and monaural features, may be used for these purposes. A Gaussian mixture model (GMM) is developed and, in some embodiments, dynamically updated for distinguishing signal from noise and performing mask-based noise reduction. Each frequency band may use a different GMM or share a GMM with other frequency bands. A GMM may be combined from two models, with one trained to model time-frequency points in which the target dominates and another trained to model time-frequency points in which the noise dominates. Dynamic updates of a GMM may be performed using an expectation-maximization algorithm in an unsupervised fashion.

Abstract: A system includes a first housing that houses a plurality of mechanical keys. A first microphone that is configured to detect a dynamic noise is located within the first housing and under the mechanical keys. A second microphone is configured to detect acoustic waves that include speech and to convert the acoustic waves into an electrical audio signal. The dynamic noise is not associated with the detected speech. The system further includes a dynamic audio signal filter that is configured to suppress, in the electrical audio signal, dynamic noise, and the dynamic audio signal filter is activated in response to the first microphone detecting the dynamic noise.

Abstract: An active noise control (ANC) system may be implemented to both sides of a fan, such that both directions of the noise emitting are treated to reduce the overall noise. The impact on airflow is minimal, and the technique is very effective in a broad range of low frequencies. Passive sound-absorbing materials may be included for attenuation of high frequencies. The resulting quiet fan produces a low level of noise compared to any other device based on fan, which produces the same capacity of airflow. The quiet fan may be incorporated in any mechanical system which requires airflow induction such as: computers, air conditioners, machines, and more.

Abstract: Noise reduction is provided to audio captured by a headset by employing spatially separated microphones provided by a headset and a mobile phone. Primary audio is captured by a headset microphone and includes both voice audio and ambient noise. Secondary audio is captured by a mobile phone microphone and includes ambient audio. Noise reduction is performed using the primary and secondary audio to generate a noise-reduce audio.

Abstract: A sound output device to be mounted in equipment, the device comprises: a memory unit configured to store correction information for at least one from among date, day and time; a sound reproducing unit configured to reproduce a sound signal representing an additional sound for an operation sound of the equipment, to read, from the memory unit, correction information corresponding to at least one of the current date, day, and time from the memory unit, and to then output a reproduced sound signal after correcting its sound pressure level in accordance with the correction information being read; and a sound output unit configured to emit the additional sound based on the sound signal outputted by the sound reproducing unit.

Abstract: An acoustic management system configured to compensate for acoustical dampening is provided. The system includes a microphone configured to detect a first acoustic signal from an acoustic environment and a logic circuit. The logic circuit detects an onset of the acoustical dampening between the acoustic environment and the microphone. The logic circuit generates an acoustic damping compensation filter, which is applied to the first acoustic signal to generate a drive signal.

Abstract: An encoding apparatus comprises a frame processor (105) which receives a multi channel audio signal comprising at least a first audio signal from a first microphone (101) and a second audio signal from a second microphone (103). An ITD processor 107 then determines an inter time difference between the first audio signal and the second audio signal and a set of delays (109, 111) generates a compensated multi channel audio signal from the multi channel audio signal by delaying at least one of the first and second audio signals in response to the inter time difference signal. A combiner (113) then generates a mono signal by combining channels of the compensated multi channel audio signal and a mono signal encoder (115) encodes the mono signal. The inter time difference may specifically be determined by an algorithm based on determining cross correlations between the first and second audio signals.

Abstract: Disclosed herein are a washing machine and a sound control method thereof that are capable of canceling noise generated during an operation of the washing machine and, at the same time, informing a user of information related to the operation of the washing machine using a sound. The sound control method includes operating the washing machine according to an inputted operation command, sensing noise generated during the operation of the washing machine, reading a sound to cancel the sensed noise, and outputting the read sound in a state in which the read sound is mapped with the noise. Consequently, it is possible mask the noise, thereby minimizing the noise. Also, it is possible to sense a start and an end of each operation and a change of the operation based on the noise pattern, sense a user's access to the washing machine, and output a feedback sound, thereby informing of the progress information of the washing machine.

Abstract: One embodiment of the present invention provides a system that manages the acoustic noise produced by a device. During operation, the system receives a set of acoustic characteristics for the device. The system then uses these acoustic characteristics to estimate the acoustic noise being generated by the device. Next, the system uses the estimated acoustic noise to adjust a setting in the device to manage the acoustic noise produced by the device.

Abstract: A system and method for reduce noise emitted by a printer are disclosed herein. In one embodiment, a sound detector disposed proximate to a noise source detects a measured noise signal, which is analyzed to determine one or more resonant frequencies thereof. A feedback signal is determined based on the analyzed noise signal and is used to generate a compensated signal 180 degrees out of phase with the feedback signal. The compensated signal is output proximate to the noise source.

Abstract: A CT system is provided that includes an outer housing, a rotatable gantry positioned within the outer housing and having a gantry opening to receive an object to be scanned, an x-ray source mounted on the rotatable gantry and configured to project an x-ray beam toward the object, and a detector array mounted on the rotatable gantry and configured to detect x-ray energy passing through the object and generate a detector output responsive thereto that can be reconstructed into an image of the object. A hybrid noise mitigation system is included in the CT system that is configured to mitigate noise generated by the CT system during operation, the hybrid noise mitigation system comprising a passive noise mitigation device configured to control noise in a passive manner and an active noise mitigation device configured to control noise in an active manner.

Abstract: A method and a system for the active reduction, at a predetermined area, of the energy of a sound signal (dk(n)), also called a diffused noise signal, generated at the area by a primary signal (xk(n)), or noise signal, by the emission of a plurality of counter-noise signals (yk(n)) having an effect antagonistic to the diffused noise signal (dk(n)), each of the counter-noise signals (yk(n)) including a feedback counter-noise signal (yfbkk(n)) and a feed-forward counter-noise signal (yfwdk(n)). The method includes detecting the periodical components of diffused noise signal (dk(n)) for adjusting the feedback counter-noise signal (yfbkk(n)), and modelling the inverse of the secondary path for adjusting the feedback counter-noise (yfbkk(n)) and feed-forward counter-noise (yfwdk(n)) signals. The invention can be implemented to any type of industrial or non-industrial noise and in any location such as working places and relaxation places.

Abstract: A system and method for controlling noise produced by an air handling system, for example, is provided. The system includes a source microphone to collect sound measurements from the air handling system and a processor to define a cancellation signal that at least partially cancels out the sound measurements. The system also includes a speaker to generate the cancellation signal. The sound measurements are at least partially canceled out within a region of cancellation. Accordingly, the system further includes a response microphone to collect response sound measurements at the region of cancellation. The processor tunes the cancellation signal based on the response sound measurements.

Abstract: An echo suppressing system includes: a sound output device for outputting sound based on a sound signal, including a passing section for allowing passage of a component of a different frequency band, and a plurality of sound output sections, each of which outputs sound based on each of the plurality of sound signals passed through the passing section; a summer for summing the plurality of sound signals to generate a reference sound signal; a sound input device for converting input sound into a sound signal; and an echo suppressor for suppressing echo based on the sound output by the sound output device, including an input section to which a sound signal is input from the sound input device as an observation sound signal, and a correction section for correcting the observation sound signal so as to suppress echo included in the observation sound signal.

Abstract: An active noise reduction system that reduces the incidence of divergence in the presence of high amplitude interfering noise. A limited frequency range threshold is established.

Abstract: An electronic device includes an enclosure for the electronic device and a duct extending from an interior to an exterior of the enclosure to exhaust airflow from the enclosure. The electronic device further includes an active noise control mechanism. The active noise control mechanism includes an internal sensor, an external sensor, and an acoustic wave generator. The internal sensor is arranged within the enclosure to sense a noise and generate an internal sensor output, and the external sensor is arranged outside of the enclosure to detect sounds and generate an external sensor output. Based on the internal sensor output and the external sensor output, the acoustic wave generator generates an acoustic wave within the duct to reduce the noise.

Abstract: A noise extraction device of the present invention includes: first and second microphone units (11 and 12) each picking up a sound; a directivity synthesis unit which performs a directivity synthesis on output signals respectively received from the first and second microphone units (11 and 12) and generates two directionally synthesized signals which have: different sensitivities to noise; the same directional pattern with respect to sound pressure; and the same effective acoustic center position; and an acoustic cancellation unit which cancels an acoustic component of one of the two directionally synthesized signals by subtracting the one of the two directionally synthesized signals from the other of the two directionally synthesized signal, so as to extract a noise component.

Abstract: To provide a noise control system capable of generating a noise cancellation field where noise is reduced at a desired position in a space. An error scanning filter generates a noise cancellation signal using an adaptive control algorithm based on error scanning, the signal having a phase opposite to that of an acoustic signal component detected by a reference sensor. A control speaker radiates the noise cancellation signal to create a noise cancellation field near the head of a person receiving sound.

Abstract: A fan control system includes a controller that is coupled to a plurality of fan couplers. A computer-readable medium is coupled to the controller and includes a first fan identification corresponding to a first fan, a second fan identification corresponding to a second fan, and at least one fan property associated with each of the first fan identification and the second fan identification. The controller is operable to monitor at least one operating parameter of each of the first fan and the second fan when the first fan and the second fan are coupled to a respective fan coupler. The controller is further operable to use the at least one fan property associated with each of the first fan identification and the second fan identification and the at least one operating parameter of each of the first fan and the second fan in order to adjust a speed of the second fan relative to a speed of the first fan.

Abstract: The present examples provide for the cancellation, or substantial reduction, of fan noise typically encountered in equipment cooling applications. Local audio nulls may be created by adjusting fan velocity and/or phase to cancel the fan noise near an operator. In a first example, phase and velocity of the fan may be controlled by feedback techniques. This technique utilizes feedback provided by a microphone located in the proximity of the operator to create an area of audio nulling of the fan noise. Local audio nulls may also be created by manipulating fan, phase and velocity by a controller that implements a process to create local audio nulls using the fixed position of equipment and the operator in the determination.

Abstract: A noise control system is directed to the path along which the noise is transmitted from the source of the noise being generated to the receiver of the noise in the passenger compartment of an automotive vehicle. The noise control system is deployed in a box structure, such as the dual bulkhead of the dashboard of the vehicle, to provide a constrained volume within which engine noise can be controlled. The dual bulkhead plenum houses an active noise control apparatus, such as a speaker or a vibrating device, between the bulkheads to be operable with a control algorithm to generate sound that can control the noise or vibrations generated by the engine. The plenum can also be treated with passive noise control materials, such as viscoelastic damping materials, acoustical foam or heavy vinyl barrier and foam to block airborne sound and vibrations, in addition to the active noise control.

Abstract: The invention relates to a method for adapting a vibration isolation system as well as to an arrangement with a vibration isolation system. By constructive measures in the environment of the vibration isolation system, particularly plane-parallel surfaces areas are avoided and thereby disturbing environmental influences are reduced.

Abstract: A noise control system operable within a box-like structure provided by the dual bulkhead plenum of the vehicle dashboard positioned within the transfer path along which the noise is being transmitted from the source of the generated noise to the receiver of the noise in the passenger compartment of an automobile. The plenum is divided into discrete chambers into each of which is provided smart materials affixed to the walls of the plenum to be operable for selectively changing a property characteristic of the chambers to vary the acoustic resonance of the plenum and change the effectiveness of controlling the transmission of noise energy therethrough. A controller is coupled to the smart materials to change said property characteristic of the smart material in response to noise cancellation requirements.

Abstract: In a communication machine room wideband noise suppression system, a sensing unit detects a noise source produced by a fan during the operation thereof and generates a noise input signal and a feedback signal, which are sent to a signal amplifying unit for signal amplification. The amplified signals are then sent to a signal converting unit and converted into digital signals. A multi-channel hybrid controller receives the digital signals and makes corrections and conduct rapid convergence algorithm to derive a reverse digital signal, which is sent to the signal converting unit and converted into a reverse analog signal. The reverse analog signal is sent to the signal amplifying unit for power amplification to generate a control signal for driving a loudspeaker unit to produce interfering acoustic wave, so as to cancel out the noise source and achieve the purpose of eliminating wideband noise.

Abstract: The present invention is an ambient noise canceling physiological acoustic monitoring system and method. The system and method utilizes a plurality of microphones to collect input data including ambient noise signals, bed frame noise signals and patient respiratory and cardiac data signals. The system and method cancels the ambient noise and bed frame noise signals, and calculates a filtered audio output signal with an algorithm that utilizes ECG rhythm patterns and impedance pneumography. The set of input data and the filtered audio output signal are then displayed in real time.

Abstract: A passive noise reduction apparatus for altering predetermined sound levels of a sound producing device, the noise reduction apparatus includes at least one piezoelectric foil sensor disposed relative to the sound producing device with the at least one piezoelectric foil sensor being operable to convert such sound wave energy into an electric sound signal and one or more electric circuits in electrical communication with the at least one piezoelectric foil sensor for receiving the electric sound signal and shunting the electric sound signal to a ground connection, thereby reducing sound heard outside the sound producing device.

Abstract: A sound altering apparatus for altering predetermined sound levels of a sound producing device, the sound altering apparatus includes at least one piezoelectric foil sensor disposed relative to the sound producing device with the at least one piezoelectric foil sensor being operable to convert such sound wave energy into an electric sound signal one or more electric circuits in electrical communication with the at least one piezoelectric foil sensor for receiving the electric sound signal and shunting the electric sound signal to a ground connection, or to produce cancelling sound wave energy in the vicinity of the sound producing device, thereby reducing sound heard outside the sound producing device.