JPH10209889A - Periodic noise elimination device and periodic noise eliminating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate periodic noise from an input signal with the periodic noise superimposed thereon and having one or a plurality of non-signal blocks. SOLUTION: A non-signal block detection section 11 discriminates a signal block and a non-signal block of an input signal. A noise estimate section 12 assumes a noise model of periodic noise included in the input signal for the non-signal block to estimate parameters of the noise model. A noise reproduction section 13 reproduces the periodic noise from the parameters of the estimated noise model. A noise elimination section 14 subtracts the reproduced periodic noise from the input signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus and a method for removing a periodic noise component from an input signal on which a periodic noise is superimposed, and more particularly to an apparatus and a method for removing a hum.

[0002]

2. Description of the Related Art In some cases, an AC component (hum) from a commercial power supply is mixed in a sound signal recorded by a microphone or a measurement signal by a sensor. The causes include insufficient removal in the power supply circuit and jumping into the high impedance transmission system from the air. Similarly, when there is a device such as a motor near the measurement system, periodic noise due to the influence may be mixed. Generally, it is expensive to remove them completely.

Conventionally, various periodic noise elimination devices have been proposed. For example, Japanese Unexamined Patent Application Publication No. 61-85063 (hereinafter referred to as Prior Art 1) discloses that a hum waveform is obtained from a measuring device using a sensor by a filter, synchronized with a delay, subtracted from a measured signal, and removed. A method for doing so is disclosed.

Japanese Utility Model Laid-Open Publication No. 63-111105 (hereinafter referred to as prior art 2) discloses a method of directly extracting a waveform of a commercial power supply in parallel with a measurement signal, and controlling and subtracting the amplitude and phase. Is disclosed.

Further, Japanese Patent Application Laid-Open No. 5-303385 (hereinafter referred to as Prior Art 3) discloses that an input signal is sampled at a sampling frequency that is substantially an integral multiple of the period of the periodic noise, accumulated, averaged, and stored. To remove the periodic noise by subtracting from

[0006]

The prior art described above has the following problems.

According to the method disclosed in Prior Art 1, if a hum waveform is obtained and other signals are sufficiently suppressed, the desired effect can be obtained. However, it is difficult to extract only the hum component from the signal, especially when the hum component is included in the spectrum of the required signal such as an audio signal. Also,
A non-periodic noise may be superimposed on the measurement signal in addition to the periodic noise. If the waveform is used as it is, there is a problem that the signal is modulated by the non-periodic noise. Furthermore, in the method of directly subtracting the waveform, the amplitude of the periodic component,
When each element such as the frequency fluctuates, the noise component cannot be completely removed, but an extra noise component is added.

In the method disclosed in Prior Art 2, it is necessary to simultaneously observe the power supply waveform at the time of waveform measurement. This imposes a heavy burden on measurement and cannot be applied to signals for which no power supply waveform is recorded.

Further, in the method disclosed in the prior art 3, the period of the noise needs to be known in advance.

Accordingly, an object of the present invention is to provide a frequency noise elimination apparatus having one or a plurality of non-signal sections and capable of removing periodic noise from an input signal on which periodic noise is superimposed. It is in.

More specifically, an object of the present invention is to obtain an audio signal from which hum noise has been removed from an audio signal superimposed on the hum noise of an AC power supply.

[0012]

According to the present invention, there is provided a periodic noise eliminator for removing a periodic noise from an input signal having at least one non-signal section and having a periodic noise superimposed thereon. A non-signal section detection unit for discriminating between a signal section of the input signal and the non-signal section, and assuming a noise model of periodic noise included in the input signal in the non-signal section, the parameters of the noise model A noise estimating unit for estimating, a noise regenerating unit for regenerating periodic noise from parameters of the estimated noise model, and a noise removing unit for subtracting the regenerated periodic line noise from the input signal. Is obtained.

According to the present invention, there is provided a periodic noise elimination method for eliminating the periodic noise from an input signal having at least one non-signal section and having the periodic noise superimposed thereon. Discriminating between a signaled section and the non-signaled section; estimating a parameter of the noise model assuming a noise model of periodic noise included in the input signal in the non-signaled section; A method of removing periodic noise from the parameters of the noise model obtained, and a step of subtracting the reproduced periodic line noise from the input signal.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a configuration of a periodic noise eliminator according to a first embodiment of the present invention. The illustrated periodic noise elimination device includes a no-signal section estimation unit 11, a noise estimation unit 12,
It has a noise reproduction unit 13 and a waveform reduction unit 14.

The no signal section estimating section 11 estimates an input signal or a no signal section. The “non-signal section” here does not mean a section where the signal amplitude is 0, but indicates a section where the target signal does not exist. For example, if the input signal is a speech signal, this is a section where no noise is generated and only a noise signal exists. For this, there is a method of estimating a portion where the short-time average power of the input signal is below the threshold value as a no-signal section.

The noise estimator 12 estimates a characteristic (parameter) of the input signal from a subsequence estimated to be a no-signal section by the no-signal section estimator 11 in accordance with a preset noise model. The noise model may be a single waveform shape or a mathematical model representing the same, or may be selected from a plurality of them. When selecting from a plurality, it becomes one of the parameters of the selected item itself.

The noise reproducing unit 13 reproduces periodic noise from the estimated parameters according to a noise model. Here, the parameters include, for example, a basic cycle (frequency),
The waveform shape, amplitude, and phase for the basic period are grouped. Also,
As an example of another parameter, a set of a basic cycle, a time series of frequency characteristics for the basic cycle, an amplitude, and a phase may be used. Still other examples of parameters include types of basic waveform shapes (sine wave, rectangular wave, triangular wave, etc.), parameters for determining the shape (for example, duty ratio in the case of a rectangular wave), basic period,
A set of amplitude and phase may be used. It is assumed that the reproduced noise continues to exist even in the portion estimated by the no-signal interval estimation unit 11 to be a signal transmission interval.

The waveform subtractor 14 removes the periodic noise component from the input signal by subtracting the reproduced noise from the input signal.

FIG. 2 shows waveforms at various parts of the periodic noise eliminator shown in FIG. In FIG. 1, the input signal is shown in the first row. The no-signal section estimation unit 11 estimates a no-signal section from the input signal as shown in the first row of FIG. The second line of FIG. 2 shows an enlarged view of the estimated no-signal section. The noise estimating unit 12 estimates parameters of the periodic noise from the no-signal section. On the basis of this parameter, the noise reproducing unit 13
Regenerate the periodic noise as shown in the row. Waveform subtraction unit 1
4 subtracts the reproduced periodic noise shown in the fourth row of FIG. 2 from the input signal shown in the first row of FIG. 2 to obtain the periodic noise as shown in the fifth row of FIG. To obtain the output signal from which

In the second embodiment of the present invention, it is assumed in the noise estimation section 12 that the periodic noise is a sine wave. This is a particularly valid assumption, such as power hum.

First, the input signal in the no-signal section is expressed as s (n)
(0 ≦ n ≦ N). In addition, it is assumed that the approximate value of the angular frequency of the sine wave is known, and is ω ₀ . This value is, for example, 50 Hz or 60 Hz for a domestic power hum.

Two points ω in the vicinity of the angular frequency shown in the following equation (1)
_L and ω _U (ω _L <ω ₀ <ω _U ) are determined. In this case, the periodic noise to be estimated so that the angular frequency omega when regarded as a sine wave becomes ω _L <ω <ω _U, chooses a width [Delta] [omega.

[0024]

(Equation 1) The cosine Fourier coefficients A (ω _L ), A (ω ₀ ) and A (ω _U ) at the angular frequencies ω _L , ω ₀ and ω _U are given by
Ask according to.

[0025]

(Equation 2) ω _L , ω ₀ , ω _U , A (ω _L ), A (ω ₀ ), A
From (ω _U ), an angular frequency ω _1c at which A (ω) takes a maximum value A (ω _1c ) is obtained using Lagrange's interpolation method as shown in Expression 3 below, and this is calculated as the angular frequency of a sine wave. Is the estimated value of.

[0026]

(Equation 3) Here, instead of the cosine Fourier coefficient, the sine Fourier coefficient B (ω _L ), B
(Ω ₀ ) and B (ω _U ), B (ω) is the maximum value B
The angular frequency ω1s taking (ω _1s ) may be used as the estimated value of the angular frequency of the sine wave.

[0027]

(Equation 4) If the input deviates from the assumption that the input is a sine wave, the above-described angular frequencies ω _1c and ω _1s do not always match. In this case, one of ω _1c and ω _1s or an average value ω 1 thereof may be used as the estimated value of the angular frequency of the sine wave. Hereinafter, whether to adopt Izure this, use omega ₁ of notation as an estimate of the angular frequency of the sine wave.

Next, Fourier coefficients A (ω ₁ ) and B (ω ₁ ) of cosine and sine at the angular frequency ω ₁ are obtained.
The assumed sine wave can be uniquely determined from the estimated angular frequency ω ₁ of the periodic noise and the Fourier coefficients A (ω ₁ ) and B (ω ₁ ) of the cosine and sine. Therefore, in the second embodiment, the noise reproducing unit 12 reproduces the noise n (t) as shown in the following Expression 5.

[0029]

(Equation 5) Referring to FIG. 3, the periodic noise eliminator according to the third embodiment of the present invention includes a waveform shape input unit 15, and a noise estimating unit and a noise reproducing unit are modified as described later. Except for this, it has the same configuration as that shown in FIG. Therefore, the noise estimating unit and the noise reproducing unit are respectively provided with reference numerals 12A and 13A, and those having the same functions as those shown in FIG. Is omitted.

The waveform shape input section 15 inputs a waveform shape. As the waveform shape, a type of waveform such as a sine wave, a triangular wave, a rectangular wave, or a mixture thereof is given.

The noise estimating unit 12A includes a waveform shape input unit 15
Based on the waveform shape and parameter type input from, the optimum frequency, amplitude and phase of the waveform are determined by maximum likelihood estimation.

The waveform shape input unit 15 outputs the waveform shape
Parameters for determining the shape of the waveform may be input simultaneously.

FIG. 4 shows an input screen of the waveform shape input section 15. Here, a rectangular wave is input as the waveform shape, and 0.3 is input as the parameter α of the rectangular wave. This parameter α gives the duty ratio of the rectangular wave as shown in FIG. The noise estimating unit 12 </ b> A obtains optimal estimation values of the frequency, amplitude, and phase of the rectangular wave input from the waveform shape input unit 15 based on the input signal. Noise reproduction unit 1
3A reproduces the periodic noise estimated by the noise estimation unit 12A based on the waveform shape input from the waveform shape input unit 15.

Referring to FIG. 6, a periodic noise eliminator according to a fourth embodiment of the present invention has a plurality of noise estimating units and a plurality of noise reproducing units in parallel, as will be described later. Thus, it has a configuration similar to that shown in FIG. That is, in the fourth embodiment, it is assumed that the periodic noise in the input signal is the sum of a plurality of waveforms whose numbers are known.
However, the illustrated example shows an example on the assumption that the periodic noise in the input signal is the sum of two waveforms. Therefore, the fourth
In the embodiment, first and second noise estimating units 12-1 and 12-2 are provided as noise estimating units, and first and second noise reproducing units 13-1 and 13-1 are provided as noise regenerating units.
-2.

The first noise estimating unit 12-1 is provided by any of the methods described in the first to third embodiments.
The first periodic noise is estimated from the input signal, and the first noise reproducing unit 13-1 reproduces the first periodic noise estimated by the first noise estimating unit 12-1. Similarly, the second noise estimating unit 12-2 estimates the second periodic noise from the input signal using any of the methods described in the first to third embodiments, and The noise reproducing unit 13-2 uses the second
The second periodic noise estimated by the noise estimating unit 12-2 is reproduced. However, the periods of the first and second periodic noises estimated by the first noise estimation unit 12-1 and the second noise estimation unit 12-2 are different from each other. The waveform subtracting unit 14 subtracts the first and second periodic noises reproduced by the first and second noise reproducing units 13-1 and 13-2 from the input signal.

Referring to FIG. 7, a periodic noise eliminator according to a fifth embodiment of the present invention includes a noise estimating unit, a noise reproducing unit, and a waveform subtracting unit as a single unit, as will be described later. Except for the cascade connection, it has the same configuration as that shown in FIG. The illustrated example is a noise estimation unit,
The figure shows an example in which units composed of a noise reproducing unit and a waveform subtracting unit are cascaded in two stages. Therefore, in the fifth embodiment, the first and second noise estimation units 1 are used as noise estimation units.
2-1 and 12-2, and first and second noise reproducing units 13-1 and 13-2 as noise reproducing units,
First and second waveform subtraction sections 14-1 as waveform subtraction sections
And 14-2.

The first noise estimating unit 12-1 is configured by any one of the methods described in the first to third embodiments.
The first periodic noise is estimated from the input signal, and the first noise reproducing unit 13-1 reproduces the first periodic noise estimated by the first noise estimating unit 12-1. First waveform subtraction unit 1
4-1 subtracts the first periodic noise reproduced by the first noise reproduction unit 13-1 from the input signal.

Subsequently, the second noise estimator 12-2
Estimates the second periodic noise from the output signal of the first waveform subtraction unit 14-1 by using any of the methods described in the first to third embodiments, and reproduces the second noise Part 13-
2 reproduces the second periodic noise estimated by the second noise estimator 12-2. The second waveform subtraction unit 14-1
The second periodic noise reproduced by the second noise reproduction unit 13-2 is subtracted from the output signal of the first waveform subtraction unit 14-1.

Referring to FIG. 8, a periodic noise eliminator according to a sixth embodiment of the present invention includes a plurality of waveform shape input units, a noise estimation unit, and a noise reproduction unit in parallel, as described later. Except for this point, it has a configuration similar to that shown in FIG. That is, in the sixth embodiment, it is assumed that the periodic noise in the input signal is the sum of a plurality of waveforms whose numbers are known. However, the illustrated example shows an example on the assumption that the periodic noise in the input signal is the sum of two waveforms. Therefore, in the sixth embodiment, first and second waveform shape input units 15-1 and 15-2 are provided as waveform shape input units, and first and second noise estimating units 12A- as noise estimating units. 1 and 12A-2, and first and second noise reproducing units 13A-1 and 13A-2 as noise reproducing units.

First and second waveform shape input units 15-1
And 15-2 input the first and second waveform shapes, respectively. First and second noise estimation units 12A-1
And 12A-2 estimate noise parameters according to the input first and second waveform shapes, respectively.
First and second noise reproducing units 13A-1 and 13A-
2 are the first and second waveform shape input units 15
-1 and 15-2 based on the first and second waveform shapes input from the first and second noise estimators 12A.
Regenerate the first and second periodic noise estimated at -1 and 12A-2. The waveform subtracting section 14 converts the input signal into first and second noise reproducing sections 13A-1 and 13A-1.
The first and second periodic noises reproduced in A-2 are subtracted.

FIG. 9 shows an actual waveform relationship in the sixth embodiment. Here, the first waveform shape input in the first waveform shape input unit 15-1 is illustrated by the input waveform 1 as shown in the second row of FIG. 9, and the second waveform shape input unit The second waveform shape input in 15-2 is illustrated by the input waveform 2 as shown in the fourth row of FIG. The first noise estimating unit 12A-1 determines the optimum basic period, amplitude, and phase for the input waveform 1 that fits the first noise waveform to be estimated in the same manner as in the third embodiment. The first noise reproduction unit 13A-1 reproduces the noise 1 as shown in the third row of FIG. Similarly,
The second noise estimating unit 12A-2 determines the optimum basic period, amplitude, and phase for the input waveform 2 that fits the second noise waveform to be estimated in the same manner as in the third embodiment. The second noise reproduction unit 13A-2 reproduces the noise 2 as shown in the fifth row of FIG. The waveform subtraction unit 14
From the input signal, these two noises 1 and 2 (ie, the noise waveform to be estimated shown in the first row of FIG. 9)
Is subtracted.

Referring to FIG. 10, a periodic noise eliminator according to a seventh embodiment of the present invention includes:
It has the same configuration as that shown in FIG. 3 except that the waveform shape input unit, the noise estimation unit, the noise reproduction unit, and the waveform subtraction unit are cascaded in a plurality of stages as one unit. The illustrated example shows an example in which units including a waveform shape input unit, a noise estimation unit, a noise reproduction unit, and a waveform subtraction unit are cascaded in two stages. Therefore, in the fifth embodiment, the first and second waveform shape input units 15-1 and 15-2 are provided as the waveform shape input unit, and the first and second waveform shape input units are provided as the noise estimation unit.
, And first and second noise reproducing sections 13A-1 and 13A-2 as noise reproducing sections, and first and second waveform subtracting sections as waveform subtracting sections. 14-1 and 14-2.

That is, the seventh embodiment is different from FIG.
In the same manner as the fifth embodiment described with reference to FIG.
The parameter concerning the waveform shape is estimated.

Referring to FIG. 11, a periodic noise elimination apparatus according to an eighth embodiment of the present invention includes
It has the same configuration as that shown in FIG. 7 except that the first and second noise estimation units are modified. Therefore, reference numerals 12B-
1 and 12B-2. Here, as an example,
It is assumed that the periodic noise in the input signal is the sum of the two waveforms.

The first noise estimating unit 12B-1 estimates the first periodic noise from the input signal by the method described in the first to third embodiments, and outputs the first noise regenerating unit. 13-
Reference numeral 1 reproduces the periodic noise estimated by the first noise estimation unit 12B-1. Here, the angular frequency ω ₁ of the waveform of the first periodic noise estimated by the first noise estimating unit 13B-1 is
This is the basic angular frequency of the waveform to be estimated.

The second noise estimating unit 12B-2 sets the angular frequency to a predetermined integer coefficient multiple nω ₁ of the estimated basic angular frequency ω ₁ , and otherwise sets the first to third frequencies described above. In the method described in the embodiment, the first waveform subtraction unit 14
−1, the angular frequency ω _{1 of} the first periodic noise
The parameters of the second periodic noise other than are estimated. Second
The noise reproducing unit 13-2 reproduces the second periodic noise estimated by the second noise estimating unit 12B-2. The second waveform subtraction unit 14-2 subtracts the second periodic noise reproduced by the second noise reproduction unit 13-2 from the output signal of the first waveform subtraction unit 14-1.

Referring to FIGS. 12 and 13, a description will be given of a periodic noise removing apparatus according to a ninth embodiment of the present invention. In the ninth embodiment, the no-signal section estimation unit 11
In, two non-signal sections are detected. The waveform at this time is shown in FIG. Here, the detected two non-signal sections are represented by times t1 and t2 shown in FIG. 12, respectively (t1 <t2). As described above, it is considered that the angular frequency that defines the periodic noise is not constant but varies with time. Here, in the no-signal section represented by times t1 and t2, the angular frequencies of the noise waveform estimated by the method described in the above-described embodiment are ω (t1),
ω (t2). At this time, as shown in FIG. 13, the angular frequency ω (t) of the periodic noise at time t is smoothly interpolated. Specifically, linear interpolation is performed according to the following equation (6).

[0048]

(Equation 6) The present invention is not limited to the above-described embodiment, and various changes and modifications can be made without departing from the spirit of the present invention.
For example, when there are three or more non-signal sections in an input signal, a representative point can be similarly taken to interpolate. Instead of linear interpolation, it is also possible to use spline interpolation. Further, not only the estimated angular frequency of the periodic noise but also the estimated parameters such as the amplitude and the phase can be similarly interpolated.

[0049]

As described above, according to the present invention, one or a plurality of non-signal sections are discriminated from an input signal, periodic noise is estimated from an input signal of the discriminated non-signal section, and the estimated periodicity is determined. Since the noise is reproduced, the periodic noise can be removed from the input signal on which the periodic noise is superimposed. Such an input signal includes, for example, an audio signal on which hum noise of an AC power supply is superimposed.Even if the hum noise cannot be completely removed at the stage of recording the sound, the hum noise is substantially completely removed in a subsequent process. It is possible to do.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a frequency noise removing apparatus according to a first embodiment of the present invention.

FIG. 2 is a waveform chart for explaining signal waveforms of respective parts of the frequency noise elimination device shown in FIG.

FIG. 3 is a block diagram showing a frequency noise removing device according to a third embodiment of the present invention.

FIG. 4 is a diagram showing an example of an input screen of a waveform shape input unit used in the frequency noise elimination device shown in FIG. 3;

FIG. 5 is a diagram for explaining waveform parameters shown in FIG. 4;

FIG. 6 is a block diagram showing a frequency noise removing device according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram showing a frequency noise elimination device according to a fifth embodiment of the present invention.

FIG. 8 is a block diagram showing a frequency noise removing device according to a sixth embodiment of the present invention.

FIG. 9 is a waveform diagram showing waveforms at various parts for explaining the operation of the frequency noise elimination device shown in FIG. 8;

FIG. 10 is a block diagram showing a frequency noise removing device according to a seventh embodiment of the present invention.

FIG. 11 is a block diagram showing a frequency noise elimination device according to an eighth embodiment of the present invention.

FIG. 12 is a diagram for explaining a relationship between a waveform and a time representing a no-signal section in the frequency noise elimination device according to the ninth embodiment of the present invention.

FIG. 13 is a diagram for explaining a relationship between time and angular frequency in a frequency noise elimination device according to a ninth embodiment of the present invention.

[Explanation of symbols]

11 No-signal section estimation unit 12, 12A, 12-1, 12-2, 12A-1, 12
A-2, 12B-1, 12B-2 Noise estimation unit 13, 13A, 13-1, 13-2, 13A-1, 13
A-2 Noise reproduction unit 14, 14-1, 14-2 Waveform subtraction unit 15, 15-1, 15-2 Waveform shape input unit

Claims (16)

[Claims] An apparatus for removing periodic noise from an input signal having at least one non-signal section and superimposed with periodic noise, comprising: a signal section of an input signal; A no-signal section detecting unit that determines a signal section; a noise estimating unit that estimates a parameter of the noise model assuming a noise model of periodic noise included in the input signal in the no-signal section; and A noise regenerating unit that regenerates periodic noise from parameters of the noise model obtained, and a noise removing unit that subtracts the regenerated periodic line noise from the input signal. 2. The periodic noise according to claim 1, wherein the noise estimator estimates the amplitude, phase, and frequency of the sine wave from the input signal using the noise model as a sine wave. Removal device. 3. The period according to claim 2, wherein the noise estimation unit estimates the frequency, phase, and amplitude of each sine wave by using the noise model as a sum of a plurality of sine waves. Noise remover. 4. The noise estimating unit first estimates a fundamental frequency, a phase, and an amplitude of one waveform, and sets parameters for other frequencies as integer multiples of the fundamental frequency of the one waveform. The periodic noise eliminator according to claim 3, wherein the estimation is performed. 5. The apparatus according to claim 1, further comprising an input unit for inputting a waveform shape, wherein the noise estimating unit estimates parameters using the waveform input from the input unit as the noise model. 2. The periodic noise elimination device according to item 1. 6. An input unit for inputting a plurality of waveform shapes, wherein the noise estimating unit estimates each parameter by using the noise model as a sum of the plurality of waveform shapes input from the input unit. The periodic noise eliminator according to claim 1, wherein: 7. The noise estimating unit first estimates a fundamental frequency, a phase, and an amplitude of one waveform, and sets parameters for other frequencies as integer multiples of the fundamental frequency of the one waveform. The apparatus for removing periodic noise according to claim 6, wherein the estimation is performed. 8. When at least two separate no-signal sections are detected by the no-signal section detection unit, the noise estimation unit smoothly interpolates parameters estimated in the at least two no-signal sections. The periodic noise elimination apparatus according to claim 1, wherein: 9. A periodic noise elimination method for removing a periodic noise from an input signal having at least one non-signal interval and having a periodic noise superimposed thereon, the method comprising: Discriminating a signal section; estimating parameters of the noise model by assuming a noise model of periodic noise included in the input signal in the non-signal section; and estimating parameters of the estimated noise model. A method for removing periodic noise; and a step of subtracting the reproduced periodic line noise from the input signal. 10. The cycle according to claim 9, wherein the step of estimating the noise estimates the amplitude, phase, and frequency of the sine wave from the input signal using the noise model as a sine wave. Sexual noise removal method. 11. The method according to claim 9, wherein the step of estimating the noise estimates the frequency, phase and amplitude of each sine wave using the noise model as a sum of a plurality of sine waves. Periodic noise elimination method. 12. The step of estimating the noise comprises first estimating a fundamental frequency, a phase and an amplitude of one waveform, and assuming that the frequency of the other waveform is an integral multiple of the fundamental frequency of the one waveform. The method of claim 11, wherein the parameter is estimated. 13. The apparatus according to claim 9, further comprising a step of inputting a waveform shape, wherein the step of estimating the noise estimates parameters using a waveform input from the input unit as a noise model. 3. The method for removing periodic noise according to item 1. 14. The method further comprising the step of inputting a plurality of waveform shapes, wherein the step of estimating the noise comprises estimating each parameter as a sum of the plurality of input waveform shapes with the noise model. 10. The method of claim 9, wherein:
3. The method for removing periodic noise according to item 1. 15. The step of estimating the noise includes first estimating a fundamental frequency, a phase and an amplitude of one waveform, and assuming that the frequency of the other waveform is an integral multiple of the fundamental frequency of the one waveform. 15. The method of claim 14, wherein the parameter is estimated. 16. When at least two separate no-signal sections are detected in the step of determining a no-signal section, the step of estimating the noise includes the steps of: estimating the parameters estimated in the at least two no-signal sections; 10. The periodic noise elimination method according to claim 9, wherein interpolation is performed smoothly.