Classifications

• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
  • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
  • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
  • G10K11/1787—General system configurations
  • G10K11/17879—General system configurations using both a reference signal and an error signal
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
  • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
  • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
  • G10K11/1785—Methods, e.g. algorithms; Devices
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
  • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
  • G10K2210/30—Means
  • G10K2210/301—Computational
  • G10K2210/3026—Feedback
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
  • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
  • G10K2210/30—Means
  • G10K2210/301—Computational
  • G10K2210/3027—Feedforward

Definitions

• the invention relates to a method of attenuating sound, comprising measuring at least one component of a sound field and producing attenuation sound by means of at least one actuator on the basis of the measurement result, and adjusting the measurement result by a coefficient.
• the invention further relates to an apparatus for attenuating sound, comprising at least one device measuring a component of a sound field and at least one actuator producing attenuation sound on the basis of the measurement result.
• JMC elements It is previously known to attenuate sound by using elements known as JMC elements.
• the idea of the method is to measure the sound pressure and particle velocity of a sound field and on the basis of the measurements to control actuators, i.e. means for producing attenuation sound, so as to allow a sound field to be produced which is exactly similar to the original sound field but of the opposite sign. In that case, the sound field can be completely eliminated by means of the actuators.
• a dipole actuator is driven by means of the measured sound pressure, a monopole actuator by means of the normal component of particle velocity, and a quadripole actuator by means of the tangential component of particle velocity. This method is, however, complicated and difficult to implement.
• An object of the present invention is to provide a method and apparatus by means of which sound attenuation can be implemented in a reasonably effective and simple way.
• the method of the invention is characterized in that a measurement result is adjusted with the approximation of the impedance or admittance of a sound field, and the approximation is adjusted on the basis of the measured residual sound pressure.
• the apparatus of the invention is characterized in that the apparatus comprises at least one device measuring residual sound pressure and a device producing an error signal, said apparatus being arranged to adjust the attenuation sound to be produced on the basis of the approximation of the impedance or admittance of a sound field, which has been adjusted on the basis of the measured residual sound pressure.
• the basic idea of the invention is that at least one component of the sound field is measured, and at least one actuator producing a sound field of the opposite sign is controlled on the basis of the measurement, and the result is adjusted by utilizing the approximation of the impedance or admittance of the sound field, and the approximation can be estimated and adjusted by measuring the residual sound pressure.
• Any detector or actuator can be left out of the apparatus consisting of two detectors and two actuators and replaced with the approximation of the impedance or admittance of the sound field in question.
• the idea of one preferred embodiment is that the value of the impedance or admittance is adjusted substantially continuously by measuring how high the level of the residual sound pressure is.
• An advantage of the invention is that with respect to sound attenuation very good and reliable results are achieved with a relatively simple method and apparatus.
• FIG. 1 illustrates a general diagram of an apparatus according to the invention
• FIG. 2 illustrates a general diagram of a second apparatus according to the invention
• Figure 3 illustrates a general diagram of a third apparatus according to the invention
• Figure 4 illustrates a general diagram of a fourth apparatus according to the invention
• Figure 5 illustrates an overall system of sound attenuation, utilizing the method and apparatus of the invention.
• Figure 1 illustrates a sound attenuation element 1.
• the sound attenuation element 1 comprises a detector 2 for the sound pressure p.
• the sound attenuation element 1 further comprises a detector 3 for the particle velocity.
• the device is used for indicating the normal component u x of particle velocity.
• the sound pressure detector 2 controls a dipole actuator 4 directly via a filter 5 on the basis of the measurement result of the sound pressure p.
• the dipole actuator 4 is used for producing a sound opposite to the original sound field.
• the intensity of the sound produced by the dipole actuator 4 is described with the strength f s of the dipole.
• the normal component u x of particle velocity measured with the particle velocity detector 3 is also utilized in controlling the dipole actuator 4.
• the effect of the particle velocity is taken into account by the device 6 producing a correction signal.
• the velocity component is multiplied by the approximation of the impedance H z of the sound field.
• H z p x c can be considered the initial value, where p is the density of the medium and c is the sound velocity in the medium.
• the approximation of the impedance H z is adjusted by measuring the remaining sound pressure, i.e. the residual sound pressure p res , which is sent to the device 6 producing a correction signal.
• control can be implemented with substantially no delay, and furthermore, by utilizing the velocity signal u x adjusted with the approximation of the impedance H Z) an accurate result can be achieved.
• There may be several measuring devices for the residual sound pressure p res whereby the residual sound pressure p res can be measured in several places. If the environmental conditions and sound source remain constant, it is not necessary to alter the approximation of the impedance after the desired level of attenuation has been achieved.
• FIG. 2 illustrates a second sound attenuation element 1'.
• a monopole actuator 4' is controlled via a filter 5' on the basis of the particle velocity. The intensity of the sound produced by the monopole actuator 4' is described with the volume velocity q s .
• the monopole actuator 4' is controlled by means of the sound pressure p in such a manner that the measurement result of the sound pressure p is adjusted with the approximation of the admittance H 1/z of the sound field.
• the admittance of the sound field is the inverse of the impedance of the sound field.
• the admittance function H 1/z of the sound field is adjusted in the same way as the impedance function H z of the sound field.
• Figure 3 illustrates a third sound attenuation element 1" according to the invention.
• the same numbers have the same significance as in Figures 1 and 2.
• the dipole actuator 4 is controlled directly on the basis of the sound pressure p.
• the particle velocity u x is not measured at all.
• the monopole actuator 4' is controlled with the measuring result of the sound pressure p, adjusted in the device producing a correction signal by means of the approximation of the admittance H 1/z of the sound field as in the case shown in Figure 2.
• Figure 4 illustrates a fourth sound attenuation element 1'" according to the invention.
• the same numbers have the same significance as in Figures 1 to 3.
• the monopole actuator 4' is controlled on the basis of the value of the particle velocity u x .
• the sound pressure p is not measured at all, but the dipole actuator 4 is controlled by means of the measuring result of the particle velocity u x , adjusted in the device 6 producing a correction signal by means of the approximation of the impedance H z as was explained in connection with Figure 1.
• Figure 5 illustrates an overall system of sound attenuation.
• the overall system comprises several sound attenuation elements 1 , 1', 1" or 1"' of the invention. All measuring results achieved with the measuring device 7 for residual sound pressure are collected in the system in order to influence the adjustment of each attenuation element. The adjustment of different elements may depend differently on different residual sound pressures.
• the measuring devices 7 for residual sound pressure may be mobile and even portable, whereby the minimization of the sound pressure focuses most effectively on the persons carrying the device.
• the arrangement is suitable for mediums in which sound causes a longitudinal wave motion, i.e. besides air, the medium may be e.g. another gas or a liquid.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Multimedia (AREA)
• Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
• Soundproofing, Sound Blocking, And Sound Damping (AREA)
• Devices For Supply Of Signal Current (AREA)
• Diaphragms For Electromechanical Transducers (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=8547098

Family Applications (1)

Country Status (6)

Families Citing this family (1)

Family Cites Families (3)

• 1996
  • 1996-11-20 FI FI964636A patent/FI105602B/fi not_active IP Right Cessation
• 1997
  • 1997-11-19 AU AU50544/98A patent/AU5054498A/en not_active Abandoned
  • 1997-11-19 DE DE69710928T patent/DE69710928T2/de not_active Expired - Fee Related
  • 1997-11-19 AT AT97913207T patent/ATE214191T1/de not_active IP Right Cessation
  • 1997-11-19 EP EP97913207A patent/EP1002311B1/de not_active Expired - Lifetime
  • 1997-11-19 WO PCT/FI1997/000707 patent/WO1998022933A1/en not_active Ceased

Non-Patent Citations (1)

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