US 4,435,751 AGranted

Vibration/noise reduction device for electrical apparatus

AssigneeHitachi, Ltd.

InventorsYasuro Hori, Minoru Kanoi, Kazuyuki Seino, Syuya Hagiwara

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Abstract

A vibration/noise reducing device for applying contrary vibrations/sound waves whose phases are substantially opposite to vibrations/noises generated from an electrical apparatus is disclosed, in which the vibrations/noises from the electrical apparatus are sensed by a sensor, the sensed analog time-domain signal is A/D converted, the resulting digital time-domain signal is then Fourier-transformed, the resulting Fourier-transformed digital frequency-domain signal is modified in its amplitude/phase to produce a second digital frequency-domain signal for generating a vibration/noise reducing control signal, the second digital-frequency-domain signal is inverse-Fourier-transformed, the resulting inverse-Fourier transformed second digital time-domain signal is D/A converted, and the resulting analog time-domain signal is used as the control signal to generate the contrary vibration/sound waves to be applied to the vibrations/noises.

Claims33

Dependent claims

A device for reducing vibrations of an electrical apparatus comprising;

sensor means for sensing said vibrations generated by said electrical apparatus to produce a first analog time-domain signal,
analog-to-digital converter means for converting said first analog time-domain signal to a corresponding first digital time-domain signal,
Fourier transformation means for Fourier-transforming said digital time-domain signal to produce a first digital frequency-domain signal,
control means responsive to said first digital frequency-domain signal to produce a vibration-reducing second digital frequency-domain signal, said control means including first, second and third memory means, comparing means and control signal generating means, wherein a portion of said first digital frequency-domain signal belonging to a (m+1)th time section of a unit time interval T is applied to said first memory means and stored therein while a portion of said first digital frequency-domain signal belonging to a m-th time section of the unit time period T is stored in said second memory means, wherein said comparing means compares the contents of said first, and second memory means and said control signal generating means responds to the compare result of said comparing means to modify a portion of said second digital frequency-domain signal previously produced based on the previous compare result and stored in said third memory to produce a next portion of said second digital frequency-domain signal, and wherein the contents of said first, second and third memory means are updated each time when said control signal generating means produces said modified second digital frequency-domain signal portion,
inverse Fourier transformation means for inverse-Fourier-transforming said second digital frequency-domain signal to produce a second digital time-domain signal,
digital-to-analog converter means for converting said second digital time-domain signal to a corresponding second analog time-domain signal,
means for amplifying said second analog time-domain signal, and applying vibrations corresponding to said amplified second analog time-domain signal to said electrical apparatus.

4 more elements

A device for reducing noises resulting from vibrations of an electrical apparatus comprising;

sensor means for sensing the vibrations generated by said electrical apparatus to produce a first analog time-domain signal,
analog-to-digital converter means for converting said first analog time-domain signal to a corresponding first digital time-domain signal,
Fourier transformation means for Fourier-transforming said first digital time-domain signal to produce a first digital frequency-domain signal,
control means responsive to said first digital frequency-domain signal to produce a vibration-reducing second digital frequency-domain signal, said control means including first, second and third memory means, comparing means and control signal generating means, wherein a portion of said first digital frequency-domain signal belonging to a (m+1)th time section of a unit time interval T is applied to said first memory means and stored therein while a portion of said first digital frequency-domain signal belonging to a m-th time section of the unit time period T is stored in said second memory means, wherein said comparing means compares the contents of said first, and second memory means and said control signal generating means responds to the compare result of said comparing means to modify a portion of said second digital frequency-domain signal previously produced based on the previous compare result and stored in said third memory to produce a next portion of said second digital frequency-domain signal, and wherein the contents of said first, second and third memory means are updated each time when said control signal generating means produces said modified second digital frequency-domain signal portion,
inverse Fourier transformation means for inverse-Fourier-transforming said second digital frequency-domain signal to produce a second digital time-domain signal,
digital-to-analog converter means for converting said second digital time-domain signal to a corresponding second analog time-domain signal,
means for amplifying said second analog time-domain signal, and
speaker means responsive to said amplifying means to be actuated by the amplified second analog time-domain signal to produce noise-reducing sound waves of substantially opposite phase to said noises and to cause said sound waves to interfere with said noises.

5 more elements

A device for reducing vibrations of an electrical apparatus comprising;

sensor means for sensing noises resulting from said vibrations generated by said electrical apparatus to produce a first analog time-domain signal,
analog-to-digital converter means for converting said first analog time-domain signal to a corresponding first digital time-domain signal,
Fourier transformation means for Fourier-transforming said first digital time-domain signal to produce a first digital frequency-domain signal,
control means responsive to said first digital frequency-domain signal to produce a vibration-reducing second digital frequency-domain signal, said control means including first, second and third memory means, comparing means and control signal generating means, wherein a portion of said first digital frequency-domain signal belonging to a (m+1)th time section of a unit time interval T is applied to said first memory means and stored therein while a portion of said first digital frequency-domain signal belonging to a m-th time section of the unit time period T is stored in said second memory means, wherein said comparing means compares the contents of said first, and second memory means and said control signal generating means responds to the compare result of said comparing means to modify a portion of said second digital frequency-domain signal previously produced based on the previous compare result and stored in said third memory to produce a next portion of said second digital frequency-domain signal, and wherein the contents of said first, second and third memory means are updated each time when said control signal generating means produces said modified second digital frequency-domain signal portion,
inverse Fourier transformation means for inverse-Fourier-transforming said second digital frequency-domain signal to produce a second digital time-domain signal,
digital-to-analog converter means for converting said second digital time-domain signal to a corresponding second analog time-domain signal,
means for amplifying said second analog time-domain signal, and applying vibrations corresponding to said amplified second analog time-domain signals to said electrical apparatus.

4 more elements

A device for reducing noises resulting from vibrations of an electrical apparatus comprising;

sensor means for sensing the noises resulting from said vibrations generated by said electrical apparatus to produce a first analog time-domain signal,
analog-to-digital converter means for converting said first analog time-domain signal to a corresponding first digital time-domain signal,
Fourier transformation means for Fourier-transforming said first digital time-domain signal to produce a first digital time-domain signal to produce a first digital frequency-domain signal,
control means responsive to said first digital frequency-domain signal to produce a vibration-reducing second digital frequency-domain signal, said control means including first, second and third memory means, comparing means and control signal generating means, wherein a portion of said first digital frequency-domain signal belonging to a (m+1)th time section of a unit time interval T is applied to said first memory means and stored therein while a portion of said first digital frequency-domain signal belonging to a m-th time section of the unit time period T is stored in said second memory means, wherein said comparing means compares the contents of said first, and second memory means and said control signal generating means responds to the compare result of said comparing means to modify a portion of said second digital frequency-domain signal previously produced based on the previous compare result and stored in said third memory to produce a next portion of said second digital frequency-domain signal, and wherein the contents of said first, second and third memory means are updated each time when said control signal generating means produces said modified second digital frequency-domain signal portion,
inverse Fourier transformation means for inverse-Fourier-transforming said second digital frequency-domain signal to produce a second digital time-domain signal,
digital-to-analog converter means for converting said second digital time-domain signal to a corresponding second analog time-domain signal,
means for amplifying said second analog time-domain signal, and
speaker means responsive to said amplifying means to be actuated by the amplified second analog time-domain signal to generate sound waves of substantially opposite phase to said noises and to cause said sound waves to interfere with said noises.

5 more elements

A device for reducing vibration of an electrical apparatus comprising;

sensor means for sensing vibrations generated by said electrical apparatus to produce a first analog time-domain signal whose instantaneous value represents an instantaneous amplitude of the vibration,
analog-to-digital converter means for converting said first analog time-domain signal to a corresponding first digital time-domain signal,
Fourier transformation means for successively Fourier-transforming divided sections of said first digital time-domain signal, each section having a period of a predetermined time interval, to produce first digital frequency-domain signals successively with said time interval,
means for producing second digital frequency-domain signal, successively, with said time interval, as a function of two successive first digital frequency-domain signals produced by said Fourier transformation means, said means for producing second digital frequency-domain signals including first, second and their memory means, comparing means and control signal generating means, wherein a portion of said first digital frequency-domain signal belonging to a (m+1)th time section of a unit time interval T is applied to said first memory means and stored therein while a portion of said first digital frequency-domain signal belonging to a m-th time section of the unit time period T is stored in said second memory means, wherein said comparing means compares the contents of said first, and second memory means and said control signal generating means responds to the compare result of said comparing means to modify a portion of said second digital frequency-domain signal previously produced based on the previous compare result and stored in said third memory to produce a next portion of said second digital frequency-domain signal, and wherein the contents of said first, second and third memory means are updated each time when said control signal generating means produces said modified second digital frequency-domain signal portion,
inverse Fourier transformation means for successively inverse-Fourier-transforming such second digital frequency-domain signals to produce second digital time-domain signals, successively, with said time interval,
digital-to-analog converter means for converting said second digital time-domain signals to corresponding second analog time-domain signals, each having a period of said time interval, and
means for amplifying said second analog time-domain signals, and applying vibrations corresponding to said amplified second analog time-domain signals to said electrical apparatus.

4 more elements

A device for reducing noises resulting from vibrations of an electrical apparatus comprising;

sensor means for sensing the vibrations generated by said electrical apparatus to produce a first analog time-domain signal,
analog-to-digital converter means for converting said first analog time-domain signal to a corresponding first digital time-domain signal,
Fourier transformation means for Fourier-transforming said first digital time-domain signal to produce a first digital frequency-domain signal,
control means responsive to said first digital frequency-domain signal to produce a vibration-reducing second digital frequency-domain signal, said control means including first, second and third memory means, comparing means and control signal generating means, wherein a portion of said first digital frequency-domain signal belonging to a (m+1)th time section of a unit time interval T is applied to said first memory means and stored therein while a portion of said first digital frequency-domain signal belonging to a m-th time section of the unit time period T is stored in said second memory means, wherein said comparing means compares the contents of said first, and second memory means and said control signal generating means responds to the compare result of said comparing means to modify a portion of said second digital frequency-domain signal previously produced based on the previous compare result and stored in said third memory to produce a next portion of said second digital frequency-domain signal, and wherein the contents of said first, second and third memory means are updated each time when said control signal generating means produces said modified second digital frequency-domain signal portion,
inverse Fourier transformation means for inverse-Fourier-transforming said second digital frequency-domain signal to produce a second digital time-domain signal,
digital-to-analog converter means for converting said second digital time-domain signal to a corresponding second analog time-domain signal,
means for amplifying said second analog time-domain signal, and
speaker means responsive to said amplifying means to be actuated by the amplified second analog time-domain signal to produce noise-reducing sound waves of substantially opposite phase to said noises for application against said noises to cause said sound waves to interfere with said noises.

5 more elements

A device for reducing vibrations of an electrical apparatus comprising;

sensor means for sensing noises generated by said electrical apparatus to produce a first analog time-domain signal,
analog-to-digital converter means for converting said first analog time-domain signal to a corresponding first digital time-domain signal,
Fourier transformation means for Fourier-transforming said first digital time-domain signal to produce a first digital frequency-domain signal,
control means responsive to said first digital frequency-domain signal to produce a vibration-reducing second digital frequency-domain signal, said control means including first, second and third memory means, comparing means and control signal generating means, wherein a portion of said first digital frequency-domain signal belonging to a (m+1)th time section of a unit time interval T is applied to said first memory means and stored therein while a portion of said first digital frequency-domain signal belonging to a m-th time section of the unit time period T is stored in said second memory means, wherein said comparing means compares the contents of said first, and second memory means and said control signal generating means responds to the compare result of said comparing means to modify a portion of said second digital frequency-domain signal previously produced based on the previous compare result and stored in said third memory to produce a next portion of said second digital frequency-domain signal, and wherein the contents of said first, second and third memory means are updated each time when said control signal generating means produces said modified second digital frequency-domain signal portion,
inverse Fourier transformation means for inverse-Fourier-transforming said second digital frequency-domain signal to produce a second digital time-domain signal,
digital-to-analog converter means for converting said second digital time-domain signal to a corresponding second analog time-domain signal,
means for amplifying said second analog time-domain signal, and applying vibrations corresponding to said amplified second analog time-domain signal to said electrical apparatus.

4 more elements

A device for reducing noises resulting from vibrations of an electrical apparatus comprising;

sensor means for sensing noises generated by said electrical apparatus to produce a first analog time-domain signal,
analog-to-digital converter means for converting said first analog time-domain signal to a corresponding first digital time-domain signal,
Fourier transformation means for Fourier-transforming said first digital time-domain signal to produce a first digital frequency-domain signal,
control means responsive to said first digital frequency-domain signal to produce a vibration-reducing second digital frequency-domain signal, said control means including first, second and third memory means, comparing means and control signal generating means, wherein a portion of said first digital frequency-domain signal belonging to a (m+1)th time section of a unit time interval T is applied to said first memory means and stored therein while a portion of said first digital frequency-domain signal belonging to a m-th time section of the unit time period T is stored in said second memory means, wherein said comparing means compares the contents of said first, and second memory means and said control signal generating means responds to the compare result of said comparing means to modify a portion of said second digital frequency-domain signal previously produced based on the previous compare result and stored in said third memory to produce a next portion of said second digital frequency-domain signal, and wherein the contents of said first, second and third memory means are updated each time when said control signal generating means produces said modified second digital frequency-domain signal portion,
inverse Fourier transformation means for inverse-Fourier-transforming said second digital frequency-domain signal to produce a second digital time-domain signal,
means for amplifying said second analog time-domain signal, and
speaker means responsive to said amplifying means to be actuated by the amplified second analog time-domain signal to generate sound waves of substantially opposite phase to said noises for application against said noises to cause said sound waves to interfere with said noises.

4 more elements

Dependencies are inferred from the claim text.