Noise reduction system

Patent metadata

Field	Value
Publication number	US-9747885-B2
Application number	US-201615066112-A
Country	US
Kind code	B2
Filing date	Mar 10, 2016
Priority date	Mar 26, 2015
Publication date	Aug 29, 2017
Grant date	Aug 29, 2017

Abstract

According to one embodiment, a noise reduction system for reducing noise including impact noise repetitively generated at a time interval includes the following elements. The error signal generator generates an error signal based on the noise being detected. The delay signal generator has a time delay characteristic and delays a signal, which is generated based on the error signal, to generate a delay signal, the time delay characteristic being determined based on an imaging sequence or pre-scanning by the MRI device and corresponding to the time interval. The control filter generates the first control signal from the delay signal. The loudspeaker unit includes at least one pair of a first filter and a control loudspeaker and a transmission unit.

First claim

What is claimed is:

1. A noise reduction system for reducing noise generated from an MRI device and including impact noise repetitively generated at a time interval, the system comprising:
an error signal generator that generates an error signal based on the noise being detected;
an estimated noise generator that generates an estimated noise signal based on the error signal and a first control signal, the estimated noise signal indicating an estimate of a sound pressure of the noise;
a delay signal generator that has a time delay characteristic and delays the estimated noise signal to generate a delay signal, the time delay characteristic being determined based on an imaging sequence or pre-scanning by the MRI device and the time delay characteristic corresponding to the time interval of the repetitively generated impact noise;
a control filter that generates the first control signal from the delay signal; and
a loudspeaker unit including at least one pair of a first filter and a control loudspeaker and a transmission unit, the first filter generating a second control signal from the first control signal, the control loudspeaker converting the second control signal to a sound wave to output a control sound, the transmission unit transmitting the control sound.

2. The system according to claim 1 , wherein the loudspeaker unit includes one pair of the first filter and the control loudspeaker,
the transmission unit includes a resonance box to which the control loudspeaker is attached, and a tube which is connected to the resonance box and transmits the control sound, and
a filter characteristic of the first filter is a through characteristic or an approximate inverse characteristic of a secondary path characteristic indicating a path characteristic from the first control signal to the error signal generator.

3. The system according to claim 1 , wherein the loudspeaker unit includes a plurality of pairs of first filters and control loudspeakers,
the transmission unit includes resonance boxes to which the control loudspeakers are attached, a sound collection unit which is connected to the resonance boxes via tubes and combines control sounds output from the control loudspeakers to generate a composite control sound, and a tube which is connected to the sound collection unit and transmits the composite control sound, and
path characteristics from the control loudspeakers to the error signal generator are different from each other, and the first filter is configured such that a secondary path characteristic indicating a path characteristic from the first control signal to the error signal generator coincides with a target transmission characteristic.

4. The system according to claim 1 , wherein a filter characteristic of the control filter is an inverse characteristic of a secondary path characteristic indicating a path characteristic from the first control signal to the error signal generator, and
the time delay characteristic is based on a value obtained by subtracting a time not less than a delay of the secondary path characteristic from the time interval.

5. The system according to claim 1 , further comprising a filter updating unit including:
a second filter that has an estimated secondary path characteristic based on a result of identifying a secondary path characteristic indicating a path characteristic from the first control signal to the error signal generator, and generates a first auxiliary signal from the delay signal; and
an updating unit that adaptively updates the control filter by using the estimated noise signal and the first auxiliary signal,
wherein the time delay characteristic is based on a value obtained by subtracting a time not less than a delay of the secondary path characteristic from the time interval.

6. The system according to claim 5 , wherein an initial state of the control filter is identical to an inverse filter of the secondary path characteristic.

7. The system according to claim 1 , further comprising:
a secondary path filter that has an estimated secondary path characteristic based on a result of identifying a secondary path characteristic indicating a path characteristic from the first control signal to the error signal generator, and generates an estimated control signal indicating an estimate of a sound pressure of the control sound at the error signal generator from the first control signal; and
a filter updating unit includes
a second filter that has the estimated secondary path characteristic and generates a first auxiliary signal from the delay signal,
a third filter that converts the first auxiliary signal in accordance with a filter characteristic identical to a filter characteristic of the control filter,
a subtractor that subtracts a signal output from the third filter from the estimated control signal to generate a second auxiliary signal, and
an updating unit that adaptively updates the control filter by using the estimated noise signal, the first auxiliary signal, and the second auxiliary signal,

wherein the time delay characteristic is based on a value obtained by subtracting a time not less than a delay of the secondary path characteristic from the time interval.

8. The system according to claim 7 , wherein an initial state of the control filter is identical to an inverse filter of the secondary path characteristic.

9. The system according to claim 1 , wherein the control filter includes an inverse filter that converts the delay signal in accordance with an inverse characteristic of a secondary path characteristic indicating a path characteristic from the first control signal to the error signal generator, and an adaptive filter that generates the first control signal from a signal output from the inverse filter, and
the system further comprises a second filter that has an estimated secondary path characteristic based on a result of identifying a secondary path characteristic indicating a path characteristic from the first control signal to the error signal generator d generates a first auxiliary signal from the signal output from the inverse filter, and an updating unit that adaptively updates the control filter by using the estimated noise signal and the first auxiliary signal,
wherein the time delay characteristic is based on a value obtained by subtracting a time not less than a delay of the secondary path characteristic and a time not less than a time corresponding to one tap from the time interval.

10. The system according to claim 1 , further comprising a secondary path filter that has an estimated secondary path characteristic based on a result of identifying a secondary path characteristic indicating a path characteristic from the first control signal to the error signal generator and generates an estimated control signal indicating an estimate of a sound pressure of a control sound at the error signal generator from the first control signal,
wherein the control filter includes an inverse filter that converts the delay signal in accordance with an inverse characteristic of a secondary path characteristic indicating a path characteristic from the first control signal to the error signal generator, and an adaptive filter that generates the first control signal from a signal output from the inverse filter, and
the system further comprises a filter updating unit including a second filter that has the estimated secondary path characteristic and generates a first auxiliary signal from a signal output from the inverse filter, a third filter that converts the first auxiliary signal in accordance with a filter characteristic identical to a filter characteristic of the control filter, a subtractor that subtracts a signal output from the third filter f

Assignees

• Toshiba Kk

Inventors

• Goto Tatsuhiko
• Nishimura Osamu
• Enamito Akihiko

Classifications

• G10K11/178 Primary

  by electro-acoustically regenerating the original acoustic waves in anti-phase · CPC title

• G10K2210/3028

  Filtering, e.g. Kalman filters or special analogue or digital filters · CPC title

• G10K2210/1161

  NMR or MRI · CPC title

• G10K2210/3016

  Control strategies, e.g. energy minimization or intensity measurements · CPC title

• G10K11/17875

  using an error signal without a reference signal, e.g. pure feedback · CPC title