Method for active suppression of acoustic noise
 Device to attenuate vent system noise / 2363992Invention relates noise protection devices. Proposed active-protection noise device comprises pressure receiver 2, preamplifier 3 with controlled transmission ratio, compensator 4, inverting amplifier 5, radiator, auxiliary pressure receiver 7 and control voltage shaper 8. Auxiliary pressure receiver is arranged shifted relative to the primary one, the shift magnitude from the formula TAD≥3τs, TAD=L/s, where TAD is the output signal advance magnitude, τs is the preamplifier control circuit time constant, L is the shift of auxiliary pressure receiver relative to the main one, s is sound velocity in air. |
 Ear protectors / 2363433Invention relates to protective devices for ears. The ear protectors have a headset for passive sound absorption, a microphone placed outside the ear protectors, a loud speaker placed inside the headset, and an amplifier for amplifying acoustic signals picked up by the microphone and transmitting signals to the loud speaker. The microphone, amplifier and loud speaker are combined into a device, to be placed into a depression made in the headset. The said depression has a lower wall, which forms a partition wall between the depression and the inner side of the headset. The lower wall has a perforation or opening for the loud speaker, facing inside the headset. |
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Ear protectors / 2363433 Invention relates to protective devices for ears. The ear protectors have a headset for passive sound absorption, a microphone placed outside the ear protectors, a loud speaker placed inside the headset, and an amplifier for amplifying acoustic signals picked up by the microphone and transmitting signals to the loud speaker. The microphone, amplifier and loud speaker are combined into a device, to be placed into a depression made in the headset. The said depression has a lower wall, which forms a partition wall between the depression and the inner side of the headset. The lower wall has a perforation or opening for the loud speaker, facing inside the headset. |
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Device to attenuate vent system noise / 2363992 Invention relates noise protection devices. Proposed active-protection noise device comprises pressure receiver 2, preamplifier 3 with controlled transmission ratio, compensator 4, inverting amplifier 5, radiator, auxiliary pressure receiver 7 and control voltage shaper 8. Auxiliary pressure receiver is arranged shifted relative to the primary one, the shift magnitude from the formula TAD≥3τs, TAD=L/s, where TAD is the output signal advance magnitude, τs is the preamplifier control circuit time constant, L is the shift of auxiliary pressure receiver relative to the main one, s is sound velocity in air. |
 Method for active suppression of acoustic noise / 2368017Invention is related to facilities for protection against acoustic noise caused by operating ventilation systems in residential premises and in moving objects. Method includes excitation of additional noise fields, in which signals for excitation of additional fields with the help of negative feedback chain with application of acoustic field exciter, acoustic pressure receiver, chain of preliminary amplifier control and generator of control voltage. Besides preliminary amplifier amplification ratio is varied by supply of additional pressure receiver signal to control voltage generator input, with time of main pressure output signal advance, which satisfies the following condition: TAD≥3τc, TAD=L/c, where: TAD - value of output signal advance, τc - time constant of preliminary amplifier control circuit. |
 System of active noise damping and its application / 2411592Here is disclosed system (10) of active noise damping for active reduction of intensity of primary sound waves (16) containing control device (11), sensor (12) of error, reference sensor (13) and several exciters (14) of secondary sound waves. Exciters (14) of secondary sound waves are designed to emit waves (15) of noise damping. Also, control device (11) connected to secondary exciters (15) processes error signal (F) and reference signal ® and generates secondary signal (S) transmitted to secondary exciters (14) through corresponding communication lines to control their emission. Thus, secondary exciters (14) emit waves (15) of noise damping, which decrease error signal (F) and facilitate optimal attenuation of sound waves. Secondary exciters (14) are positioned at boundary of open passage (21) letting primary sound waves (16) to ensure active attenuation of sound waves in open space in the direction of their transmission behind open passage (21) by means of waves of noise damping operating as "acoustic screen". |
 Aircraft with better acoustic comfort / 2469909Aircraft comprises cabin. Said cabin comprises lining panels and system of active ambient noise control. Every lining panel is either active or passive panel. Active panel comprises drives supplied from aforesaid system. Panel of one type is mechanical interchangeable with that of the other type. Active panel supply wiring allows connection to active panels. Active panel supply system is connected to active panel supply wiring. Proposed method consists in that passive panel is replaced by active panel. The latter is connected to wiring of active sound control system, or active lining panel is disconnected from said system and replaced by passive panel. |
 Device for noise compensation in car / 2472237Device for noise compensation in a car with a receiver (10) which detects occurring noise, having a signal generator (8) which generates, based on the detected noise, at least one signal, and with at least one speaker (7) which generates, based on the signal, damping sound waves which are phase shifted with respect to the sound waves of the occurring noise, and emits said waves inside the car. The at least one speaker (7) is installed inside the car such that damping sound waves are emitted into the zone of the sleeping berth (11). |
 Acoustic noise generator / 2493645Acoustic noise generator includes a control unit, a display unit, an inspection unit, a power supply and battery charge unit, a battery, a low-frequency signal generator and rotation actuating unit, wherein the low-frequency signal generator is in form of a cylindrical housing, on the inner surface of which there are uniform protrusions; a rod is placed in the housing in line with the axis of the housing, with the possibility of rotation, where the same ends of bearing elements are rigidly attached, and the other ends are fitted with first contact elements with the possibility of translational displacement thereof along the bearing elements and with the possibility of interaction with protrusions of the housing; on the outer surface of the housing there are uniformly arranged second contact elements, with the possibility of interaction thereof with the housing, wherein the rod of the low-frequency signal generator is kinematically connected to the rotation actuating element. |
 Method and apparatus for suppressing narrow-band noise in passenger cabin of vehicle / 2504025Apparatus for suppressing noise in the passenger cabin of a vehicle has at least one converter, a programmable computer and at least one acoustic sensor. The computer is configured to apply the electroacoustic model of the passenger cabin to the model of an adjustment system, having a fixed coefficient master controller which is connected to a variable coefficient unit, having a Yule parameter in form of a Yule Q unit. In the method, the first step involves determining and calculating the electroacoustic model and control law for at least one predetermined noise frequency. At the second step, the computer applies the control law to the electroacoustic model in real time in accordance with the current noise frequency to be suppressed. |
FIELD: physics, acoustics.
SUBSTANCE: invention is related to facilities for protection against acoustic noise caused by operating ventilation systems in residential premises and in moving objects. Method includes excitation of additional noise fields, in which signals for excitation of additional fields with the help of negative feedback chain with application of acoustic field exciter, acoustic pressure receiver, chain of preliminary amplifier control and generator of control voltage. Besides preliminary amplifier amplification ratio is varied by supply of additional pressure receiver signal to control voltage generator input, with time of main pressure output signal advance, which satisfies the following condition: TAD≥3τc, TAD=L/c, where: TAD - value of output signal advance, τc - time constant of preliminary amplifier control circuit.
EFFECT: higher efficiency of noise suppression and operation stability under unstable acoustic conditions.
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The invention relates to techniques for damping noise outside a bounded domain containing noisy object, as well as the protection of an object from external noise. In particular the invention relates to protection against acoustic noise caused by the running ventilation systems in dwellings and mobile objects.
The basis of active methods of damping of acoustic noise and vibration is excited such additional noise and vibration fields, interference with the primary fields leads to a specific decrease of the residual noise level in the room. Different systems for active noise and vibration absorption is determined by the methods of forming the signal that excites additional fields, the diversity of their means of excitation, characteristics of objects or characteristics of the space in which is provided an active damping, etc. the best dynamic performance characteristics have active device Samogitia, in which the signals for the excitation of additional fields are provided with negative feedback circuits. Such devices contain at least one agent of the acoustic field (the loudspeaker, which is loaded on the environment) and the corresponding acoustic pressure receiver (microphone)located in the immediate vicinity is the loudspeaker.
Consider some well-known technical solutions for damping noise.
The known device for noise suppression (Copyright certificates of the USSR: №349011, 356819, 590807, 832578, 836655), the essence of which is that beeping noise received by the microphone is converted into electrical and then served on a speaker that emits sound waves of the same frequency but with a phase opposite to the incident on the microphone waves.
Device for noise suppression, containing a microphone, amplifier, phase shifter and the loudspeaker, characterized in that the core magnetic circuit of the loudspeaker with its reverse side is made a recess in which is placed the microphone, soundproof from the loudspeaker. USSR author's certificate No. 356819, IPC H04R 9/06, 1972
Device for noise suppression, containing a number of identical channels, each of which consists of series connected filter, the phase shifter and amplitude regulator, as well as a preamplifier, the output of which is connected simultaneously to filters on all channels, and the input to the sensor, the amplifier, the input of which is connected both to the outputs of the regulators amplitude of all channels and output from the loudspeaker, characterized in that to increase the degree of noise suppression across the sound field, it is equipped with a camera the noise source and the camera compensation, United have been added to the waveguides, and the loudspeaker is installed on one of the walls of the chamber compensation. USSR author's certificate No. 836655, IPC H04R 9/06, 1981
According to the authors, as emitted from the speaker the sound waves of opposite phase sound waves, noise, with the same amplitude and those of others they must extinguish each other. The above-mentioned devices differ from each other by the degree of complexity of electronic equipment that converts sound signals into electric, and then again in the sound, but opposite in phase source.
Although the emitted sound waves of the noise of the waves emitted by the device at the same frequency and, therefore, are coherent, it is not enough for uniform noise over the entire area suppression.
For uniform suppression it is necessary that the sound wave of the noise of the waves emitted by the device were not only coherent, but that it coincided according to the shape of the surface of the wave front and the direction of their propagation. Otherwise, coherent waves, coming in different points of space, will have different phases and, depending on the phase difference will be in one place to extinguish each other, and the other to increase. The shape of the wave front emitted from the device, depends on the shape of the radiating surface is.
The task of uniform noise over the entire area suppression is not solved by these devices.
A device for noise suppression, containing a microphone, a diffuser for emitting waves in antiphase waves of noise and the amplifier connected to the microphone located on the inner side of the cone, characterized in that it contains one or more vibrators located on the outer side of the cone from incoming waves of noise, the amplifier has an adjustable gain and connected to the vibrators, and for uniform noise over the entire area of the suppression of the cone has the shape close to the shape of the wavefront waves of incoming noise. The patent of Russian Federation №2115960, IPC G10K 11/16, 1998
The microphone picks up the sound of the noise, converts them into electrical signals, amplified by the amplifier and then supplied to the vibrators, which is forced to oscillate radiating surface opposite the incoming waves of noise, and the interference of the radiated waves and waves of noise, to extinguish the last. Radiating surface (cone) has the form of a wave surface incoming waves of noise, the vibrators are located on the outer side of the surface, and the microphone is on the inside. Vibrators change the phase fluctuations on the opposite when changing the polarity of the power supply. The device is difficult and in the expansion and as it is practically impossible to meet the shape of the diffuser, close the wavefront shape of the waves of incoming noise.
Device for noise suppression is intended to improve the efficiency of noise reduction. For this purpose, the proposed device has a first microphone that is connected in series with the filter, phase detector, an adjustable phase shifter and the second microphone, connected in series with block automatic gain control, filter, phase detector, an adjustable phase shifter, both microphone is loaded on the adder, consistently associated with the speaker to control the amplitude and duration and the power amplifier, while the output of the second filter of the second microphone connected to a second input of the phase detector of the first microphone. The application for the invention of the Russian Federation No. 92005264, IPC G10K 11/16, 1995
There is a method of damping noise, according to which set of measurement microphones in the nodes of the mesh structures that are placed in two layers and which borders the measuring plane. Similarly installed and exclusive sound sources. The application for the invention of the Russian Federation No. 95107190, IPC: G10K 11/16, 1996
Known way to absorb noise, which consists in measuring the excess of the noise level over the sanitary norm ΔL, wherein identifying the sources of excess noise, RA is meshaut at a distance of r> λ from the identified sources emitters infrasonic tones with a wavelength of deleting from each other d>λ/π, radiate into the surrounding space infrasonic wave, the intensity of which is determined from the ratio
,
where ΔL is the amount of excess noise level, dB; P is the intensity of the sound pressure generated by the emitter infrasonic tone, dB; PW- maximum intensity noise on the harmonica, dB; λ, λW, ΔL - wavelengths infrasonic tones and identified harmonics excess noise, refer to the Patent of Russian Federation №2078477, IPC G10K 11/16, 1997.
How active Zvukovaya is that in the direction of propagation suppressed signal waves together and collinear with her emit a wave pump with an amplitude significantly greater amplitude of the signal wave, and the frequency and initial phase of the radiated wave more than twice the frequency and initial phase of the suppressed waves. The result is increased efficiency Zvukovaya, a suppression of low-frequency signal of the high-frequency pumping. This prevents the pump bandwidth reception path locator. The patent of Russian Federation №2185666, IPC G10K 11/16, 2002
A device active damping of noise that contains the causative agent of the acoustic field (loudsp the tel, loaded on the environment) and the corresponding acoustic pressure receiver (microphone), located in front of the loudspeaker. Inverting amplifier and compensator circuit is included in the negative feedback. Part of the negative feedback circuit includes a loudspeaker and a microphone, and the microphone is connected to the input of pre-amplifier, the output of which is connected to the input of the compensator and the output of the compensator - inverting input of the amplifier, the output of which is connected to the loudspeaker. U.S. patent No. 4527282, IPC G11K 11/00, 1985.
Practical application of the device ineffective due to the lower stability under the action of random rapid changes of air pressure in the room caused by opening Windows and doors, draughts, temperature, wind, different move, etc. characterizing acoustic instability conditions of operation.
The known method and device for active damping of acoustic noise that contains the causative agent of the acoustic field (the loudspeaker), which is loaded on the environment, and the corresponding acoustic pressure receiver (microphone), located in front of the loudspeaker. Inverting amplifier and compensator included in the feedback circuit, which includes the speaker and and mi is Rofan, moreover, the output of the microphone is connected to the input of a preamplifier electrically operated transfer coefficient, the pre-amp output is connected to the input of the compensator, the output of the compensator is connected to the inverting input of the amplifier, the output of which is connected to the loudspeaker, and the control input of the pre-amplifier coupled to the output driver control voltage, the input connected to the output of the microphone.
The output voltage of the microphone is supplied simultaneously to the input of pre-amplifier with an electric control transmission coefficient and the input of the shaper control voltage, providing the adaptive change of the transmission factor of the feedback circuit under the action of a control voltage corresponding to the differential air pressure. U.S. patent No. 5848169, IPC G11 11/00, 1998 Prototype.
With the rapid changes in air pressure, the formation of the control voltage lags behind the process of formation of differential air pressure. Since the magnitude of the speed differential air pressure reaches 90 dB relative pressure characterizing the threshold of hearing, the gap formation process of the control voltage leads to the excitation of the feedback circuit of the transition process, reducing the effect of what you want to make the operation of the device active damping of noise and exciting indoor noise characteristic response, that is a significant drawback.
This invention eliminates the disadvantages of analogue and prototype.
The technical result of the invention is to increase the efficiency of Samogitia and stability in unstable acoustic conditions.
The technical result is achieved in that in the method for the active damping of acoustic noise of ventilation systems, including the initiation of additional noise fields in which the signals for the excitation of additional fields form a chain of negative feedback using acoustic exciter field acoustic pressure receiver, the control circuit preamplifier and shaper control voltage, the change in the gain of the pre-amplifier, feeding on input shaper control voltage signal additional pressure receiver, with the lead of the output signal of the main receiver pressure, satisfying the condition: Top≥3τc, Top=L/c, where Top- the value of the timing output signal, τc- the time constant of the control circuit of the preamplifier.
In the device for active damping of acoustic noise ventilation systems containing driver control voltage, the emitter and the receiver pressure is Oia, located in front of the emitter, electrically connected by a feedback circuit which sequentially installed a pre-amplifier with electrically operated transfer coefficient, the compensator and the power amplifier, which is loaded on the emitter, the output driver control voltage is connected with the control input of the pre-amplifier and its input - output receiver pressure, additional pressure receiver, the output of which is connected with the second input of the shaper control voltage, an additional receiver pressure is set with an offset relative to the base. The offset is determined from the ratio of the ratios of Top≥3τc, Top=L/c, where Top- the value of the timing output signal, τc-the time constant of the control circuit of the pre-amplifier, L - offset additional pressure receiver relative to the base, c is the speed of sound in the air.
The essence of the invention illustrated in figures 1 and 2.
Figure 1 shows the structural diagram of the device, where 1 - air channel (the input space), 2 - pressure receiver (microphone), 3 - pre-amplifier with electrically operated gear ratio, 4 - compensator, 5 - inverting amplifier, 6 - emitter, 7 - additional receiver pressure is Oia, 8 - shaper control voltage. Arrow And marked with the direction of propagation of acoustic noise.
Figure 2 presents the dependence of the efficiency of the device damping of acoustic noise In the operating frequency band of 60...500 Hz when the action in the premises of the differential air pressure 90 dB relative pressure characterizing the threshold of audibility. Dependence is obtained when the ratio of signal to noise in the feedback circuit, greater than 36 dB.
The implementation of the method here on the example of the operation of the device. Acoustic noise propagating along the ventilation channel 1 in the direction indicated by the arrow A, excites the receiver output pressure 2 (primary) voltage transmitted to the input of the pre-amplifier 3 with electrically operated transfer coefficient and the input of the shaper control voltage 8. The output voltage of the pre-amplifier 3 is fed to the input of the compensator 4. The compensator 4 provides a phase shift of spectral components of the output voltage of the amplifier 3 and reduces the overall level of noise acting on the pressure receiver 2 due to the interference of noise coming through the ventilation channel 1, and noise generated by the emitter 6, the output voltage of the inverting amplifier 5, whose input is connected to the output of the compensator 4.
Rabotastala when destabilizers the action of the differential air pressure is provided at the control input pre-amplifier 3 with electrically operated transfer coefficient of the output voltage of the shaper the control voltage 8. Input shaper control voltage 8 receives signals from the pressure receiver 2 that is installed in front of the radiator (speaker) 6, and additional pressure receiver 7 that is installed with an offset of L with respect to the pressure receiver 2, resulting in an output signal of the pressure receiver 7 is ahead of the output signal of the pressure receiver (microphone) 2. The magnitude of the timing Topdetermined from the condition Top≥3τcwhere τc- the time constant of the control circuit of the pre-amplifier 3. While Top=L/c where L is the offset of the additional pressure receiver (microphone) 7 relative to the main pressure receiver (microphone) 2, c is the speed of sound in the air.
How active damping of acoustic noise of ventilation systems, including the initiation of additional noise fields in which the signals for the excitation of additional fields form a chain of negative feedback using acoustic exciter field acoustic pressure receiver, the control circuit preamplifier and shaper control voltage, wherein changing the gain of the pre-amplifier, feeding on input shaper control voltage signal additional receiver giving is to be placed, with time, the timing of the output signal of the main receiver pressure, satisfying the condition:
Top≥3τwith, Top=L/c
where Top- the value of the timing signal output;
τwith- the time constant of the control circuit of the pre-amplifier.