JPH1084595A - Method for recovering isdn d channel without losing signaling or packet data and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sound quality of a speaker by providing a digital signal processor, converting the digital audio signal obtained from the processor into an analog signal and giving it to the speaker. SOLUTION: A digital audio signal from an A/D converter 4 is fed to a channel decode/error correction circuit 6, in which channel decoding and error correction are conducted. The digital audio signal from the circuit 6 is fed to a de-interleave/error correction circuit 7, in which the signal is de-interleaved and the error is corrected. The digital signal is fed to a D/A converter 10 as it is through the digital signal processor DSP 8, and converted into an analog signal, which is fed to a line-out terminal 14. Furthermore, the signal from the circuit 7 is converted into an analog signal by a D/A converter 11 whose characteristic is controlled by a characteristic control means 9 of the DSP 8 and the analog signal is fed to a small sized speaker 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electronic device having a built-in speaker and a portable electronic device having a built-in small speaker.

[0002]

2. Description of the Related Art For example, a conventional video camera integrated type V
The TR has an output terminal for a reproduced audio signal, and the reproduced audio signal is supplied to another VTR or a television receiver, and finally supplied to a speaker having good characteristics. Did not.

However, in the case of incorporating a speaker in a video camera-integrated VTR, a very small speaker such as a piezoelectric speaker has to be built in with the recent miniaturization of the video camera-integrated VTR. Did not get.

[0004]

However, a small speaker has a drawback that the sound quality is not so good.

Therefore, it has been found that the sound quality can be improved by controlling the audio signal supplied to the small speaker in some way. Also, it has been found that the sound quality of a large speaker can be further improved by controlling the audio signal supplied to the speaker in some way.

In view of the above, the present invention is to propose an electronic device having a built-in speaker that can improve the sound quality of the speaker.

Further, the present invention relates to a portable electronic device having a built-in small loudspeaker.
They try to suggest things that can be improved.

[0008]

According to a first aspect of the present invention, there is provided an electronic apparatus including a speaker to which an audio signal is supplied.
A digital signal processor for controlling the digitized audio signal of the audio signal to a predetermined characteristic according to the characteristics of the speaker is provided, and the digitized audio signal obtained from the digital signal processor is converted into an analog signal and supplied to the speaker. Electronic device with a built-in speaker.

According to the first aspect of the present invention, the digitized audio signal of the audio signal is supplied to the digital signal processor to obtain a digitized audio signal controlled to a predetermined characteristic according to the characteristic of the speaker. The digitized audio signal is converted into an analog signal and supplied to a speaker.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a portable electronic device, for example, a digital VTR (video tape recorder) with a built-in camera, will be described below with reference to FIG. FIG. 1 shows an audio circuit of a reproduction system of the VTR. For example, a pair of rotary magnetic heads HA and HB provided on a rotary drum of a tape guiding drum device including a fixed drum and a rotary drum, and arranged at an angular interval of 180 °, for example.
Thus, a digital audio signal (a rectangular wave is dulled and has a waveform close to a sine wave) in the reproduction signal reproduced from the inclined track of the magnetic tape T is alternately switched by the changeover switch 1 and then changed to a high frequency. The signal is supplied to the equalizing circuit 3 through the amplifier 2 and equalized. The equalized digital audio signal is supplied to the A / D converter 4 and the PLL 5, and the clock signal obtained from the PLL 5 is supplied to the A / D converter 4 so that the digital signal is output from the A / D converter 4. An audio signal is obtained.

The digital audio signal from the A / D converter 4 is supplied to a channel decode / error correction circuit 6 to be subjected to channel decoding and error correction. The digital audio signal from the channel decode / error correction circuit 6 is supplied to a deinterleave / error correction circuit 7, where it is deinterleaved and error corrected.

This deinterleave / error correction circuit 7
(For example, a 16-bit digital audio signal) is directly supplied to a D / A converter 10 through a DSP (digital signal processor) 8 to be converted into an analog signal. It is supplied to the output terminal 14. The audio signal from the output terminal 14 is supplied to the monitor receiver directly or via another VTR, and is supplied to a speaker having good sound quality.

A deinterleave / error correction circuit 7
The digital audio signal from the DSP 8 is controlled by the characteristic control means 9 of the DSP 8.
After performing the characteristic control, the analog signal is supplied to the D / A converter 11 and converted into an analog audio signal. The audio signal is transmitted through the low-frequency amplifier 13 to a small speaker (for example,
(Piezoelectric speaker) 15.

A piezoelectric speaker (piezoelectric sounding body) is thin, lightweight, occupies a small area, and has no mechanically worn parts, so that high reliability is maintained for a long period of time. The piezoelectric speaker is
Because of voltage driving, power consumption is low and driving for a long time is possible. The sound emission frequency characteristics of an example of a piezoelectric speaker are as follows: as the frequency gradually increases from 400 Hz, the sound pressure gradually increases, and after 600 Hz, the sound pressure level peaks (approximately 82 dB). As the frequency increases, the sound pressure level gradually decreases, reaches a valley (63 dB) at 900 Hz, and then increases as the frequency increases.
3 dB), and thereafter, as the frequency increases, the sound pressure level decreases, and the valley (53) exceeds 4 kHz.
dB) and then as the frequency increases, 10
It has the characteristic that the sound pressure level increases up to about kHz.
From this characteristic, it can be seen that the sound quality of the piezoelectric speaker is not so good.

FIG. 2 shows an audio circuit of a portable electronic device incorporating a small speaker, such as a portable television receiver or a portable communication terminal, which is suitable for applying the present invention. Are denoted by the same reference numerals, and redundant description will be omitted. That is, after the analog audio signal from the input terminal Tin is supplied to the A / D converter 4 and converted into a digital audio signal,
It is supplied to SP8. Other configurations are the same as those in FIG.

Next, referring to the flowchart of FIG.
An automatic gain control (AGC) unit as an example of the characteristic control unit 9 of the DSP 8 will be described. Note that the AGC shown in this flowchart is processed by the DSP 8 in an audio sampling cycle (1 / 32,000, 1 / 44,100, or
(1 / 48,000 seconds).

In step ST-1, the left and right channel audio signals (outputs) are L, R, and n sample attenuation coefficients are A [n], and the level up coefficient is Ak (where Ak is
When Ak> 1), the operation of Expression 1 is performed, and this is set as a monaural digital output M of n samples. The means for performing the calculation in step ST-1 is referred to as first calculation means.

[0018]

[Equation 1] {(L + R) / 2} × A [n] × Ak≡M

In the equation (1), if (L + R) / 2 is set to P, the equation (1) is expressed as the equation (2).

[0020]

## EQU2 ## P × A [n] × Ak≡M

In the equation (1), when L = R, P is a monaural audio signal.

Step ST-2 following step ST-1
Then, as shown in Expression 3, the expression of Expression 1 is subjected to an absolute value operation, and the operation result is set as | S |. Means for performing the calculation in step ST-2 is referred to as second calculating means.

[0023]

| (L + R) × A [n] × Ak / 2 | ≡ | S |

Step ST-3 following step ST-2
When T / H (T / H> 0) determined in consideration of the dynamic range of the entire system is used as a threshold coefficient, | S |
Is compared with a threshold coefficient T / H,

[0025]

| S |> T / H

It is determined whether or not it is. The means for performing the comparison in step ST-2 is referred to as second comparing means.

If the result of step ST-3 is YES, that is, if the equation (4) is satisfied, then in step ST-4,
When Ka (where Ka is Ka ≦ 1) is used as an attack coefficient, the dynamic range is compressed by performing the calculation shown in the equation (5).

[0028]

## EQU5 ## A [n] × Ka → A [n + 1]

(N + 1) Sample attenuation coefficient A [n + 1]
Get. Means for performing the calculation in step ST-3 is a third
Calculation means.

NO in step ST-3, that is, as shown in the equation (6),

[0031]

| S | ≦ T / H

In this case, as described below, the level is gradually expanded using the recovery coefficient so that the digital audio signal is not distorted. That is, step S
At T-5, Kc is a recovery counter coefficient, and increment α is 0.
As 001h (hexadecimal number), the counting shown in the equation (7) is performed.

[0033]

[Mathematical formula 7] Kc + 0001h → Kc

The means for counting in step ST-5 is defined as first counting means.

After step ST-5, step ST-
In equation (6), Kr is used as a recovery coefficient as shown in equation (8).
Compare Kc with Kr,

[0036]

[Expression 8] Kr> Kc

It is determined whether or not it is. Step ST-
The means for performing the comparison of No. 5 is referred to as second comparing means.

If the result of step ST-6 is YES, that is, if the equation (8) is satisfied, then in step ST-7,
An operation as shown in Expression 9 is performed to obtain an (n + 1) sample attenuation coefficient A [n + 1].

[0039]

[Equation 9] A [n] → A [n + 1]

The means for performing the calculation in step ST-6 is a fourth means.
Calculation means.

If NO in step ST-6, that is, if
When the equation of Expression 10 holds,

[0042]

[Formula 10] Kr ≦ Kc

In step ST-8, with respect to the recovery counter coefficient Kc, as shown in the equation (11),

[0044]

[Mathematical formula-see original document] The operation of Kc = 0000h is performed to set Kc to 0. The means for performing the calculation in step ST-8 is referred to as fifth calculating means.

Step ST-9 following step ST-8
And the increment α is set to 0 with respect to the recovery counter coefficient Kc.
As 001h (hexadecimal number), the count shown in the equation 12 is performed.

[0046]

A [n] + 0001h → A [n + 1]

(N + 1) Sample attenuation coefficient A [n + 1]
Get. The means for performing the counting in step ST-9 is a second means.
Counting means.

The third calculating means of step ST-4, the fourth calculating means of step ST-7, or the step ST-
9 using the (n + 1) sample attenuation coefficient A [n + 1] obtained from the second counter means in step ST-1.
, Second calculating means in step ST-2, first comparing means in step ST-3, third calculating means in step ST-4, first counter means in step ST-5, step ST -6 second comparing means, step ST
In the fourth arithmetic means of -7, the fifth arithmetic means of step ST-8, and the second counter means of step ST-9, (n + 1) is substituted for each n, and (n + 1)
Perform the sample operation. In addition, n sample attenuation coefficient A
Initial value A of [n]

[0] sets a predetermined value in advance.

Then, the initial value A of each coefficient A [n] described above is obtained.

[0], Ak, T / H, Ka, and Kr are set in accordance with the characteristics of the small speaker (for example, piezoelectric speaker) 15 in FIGS. Note that Kc is automatically determined in a range from 0000h to Kr (predetermined value represented by a 4-digit hexadecimal number).

FIG. 4 shows the input / output digital audio signal without AGC when the horizontal axis represents the level of the input analog audio signal (dB) and the vertical axis represents the level (dB) of the output analog audio signal. The input / output static characteristic line a in the case of non-control and the input / output static characteristic curve b of the input / output digital audio signal in the case where AGC is performed are shown. T / H indicates a threshold coefficient of the output analog audio signal corresponding to the threshold coefficient T / H in FIG. 3, and the level-up coefficient is an analog level-up coefficient corresponding to the level-up coefficient Ak in FIG. . According to the characteristic curve b, the level of the audio signal obtained by multiplying the input audio signal by the level-up coefficient is compared with the threshold coefficient T / H, and when the level is larger than the threshold coefficient T / H, the attack coefficient K
multiplied by a to compress the level, and threshold coefficient T /
When the value is smaller than H, the level is gradually expanded by using the recovery coefficient so that no distortion occurs in the signal.

Next, another example of the characteristic control means 9 of the DSP 8 will be described. FIG. 5 shows a characteristic of another example of the characteristic control means 9 of the DSP 8, which is an AG whose characteristic is similar to FIG.
In this case, the level obtained by multiplying the input audio signal by the level-up coefficient is a threshold coefficient T.
When the threshold coefficient T / H is exceeded as compared with / H, the linearity is lost to generate distortion and the level is compressed, but the characteristics are different from those in FIG.

FIGS. 6A and 6B show waveforms of the input and output audio signals in the case of the characteristic shown in FIG. The output audio signal of FIG. 6B is level-compressed in a portion where the absolute value level exceeds the threshold coefficient T / H, and is level-expanded in a portion below the threshold coefficient T / H, as compared with the input audio signal of FIG. 6A. You can see that.

The above-described characteristic control means 9 of the DSP 8 is a case in which the level control is performed to increase the sense of volume. However, it is also possible to perform the level control to perform noise compression at a low level. is there. FIGS. 7 and 8 show examples of such cases.
This will be described with reference to FIG.

FIG. 7 is a diagram for explaining the level control for noise reduction in the characteristic control by the characteristic control means 9 of the DSP 8, wherein A is the characteristic of the input / output audio signal, B is the waveform of the input audio signal, C indicates the waveform of the output audio signal. In this case, when the absolute value of the level of the input audio signal is equal to or lower than the threshold value T / H, the level of the output audio signal is set to 0 to reduce noise.

FIG. 8 also illustrates the characteristic control by the characteristic control means 9 of the DSP 8 for explaining the level control for noise reduction, where A is the characteristic of the input / output audio signal, B is the waveform of the input audio signal, C indicates the waveform of the output audio signal. In this case, when the absolute value of the level of the input audio signal is equal to or less than the threshold value T / H, the ratio (amplification factor) of the output audio signal to the input audio signal is reduced, and when the absolute value exceeds the threshold value T / H, Noise is reduced by increasing the ratio (amplification factor) of the output audio signal to the input audio signal.

The above-described characteristic control means 9 of the DSP 8 controls the level of the input digital audio signal. However, the following control is also possible. That is, by supplying a digitized signal of the audio signal from the microphone to the delay memory to obtain an output digital audio signal delayed for a predetermined time and supplying the analogized signal of the output digital audio signal to the speaker, Prevents howling. Further, a digitized signal of the audio signal from the microphone is supplied to the delay memory, an output digital audio signal delayed by a predetermined time is obtained, and an analog signal of the output digital audio signal is supplied to the speaker. An echo can be realized by returning the sound to be heard to the microphone.

The output digital audio signal whose tempo is changed (or the pitch is also changed) is obtained without changing the pitch (pitch) of the input digital audio signal, thereby improving the audibility of the sound. Slow playback from magnetic tape, or
A digitalized signal of an audio signal (input audio signal) reproduced at double speed is obtained as an output digital audio signal in which only the pitch is changed without changing the tempo, thereby improving the audibility of the sound. A digital signal of an audio signal reproduced at double speed from a magnetic tape is obtained without changing the pitch, and an output digital audio signal with a reduced tempo is obtained, thereby improving the audibility of the sound. An output obtained by subtracting the digitized signal of the voice signal component of the human voice (or the voice signal component other than the voice signal component of the human voice) from the digitized signal of the audio signal (input audio signal) from the microphone. A digital voice signal is obtained to improve the audibility of human voices or voices other than human voices.

As portable electronic devices incorporating a small speaker, in addition to a digital VTR integrated with a video camera, an analog VTR integrated with a camera, a digital or analog VTR without a video camera, and a portable television receiver A portable communication terminal or the like is also possible.

In the above-described embodiment, in a portable electronic device incorporating a small speaker, an input digital audio signal is supplied to the characteristic control means 9 of the DSP 8 so that the characteristic of the input digital audio signal is changed according to the characteristic of the speaker. Although the case where the controlled output digital audio signal is supplied to the small speaker has been described, generally, in an electronic device having a built-in speaker (including a large speaker), the input digital audio signal is supplied to the DSP 8. By supplying the output digital audio signal whose characteristics are controlled in accordance with the characteristics of the loudspeaker to the loudspeaker, the output digital audio signal is supplied to the loudspeaker, whereby the sound quality can be further improved.

As the electronic device incorporating a speaker (including a large speaker), a stationary analog or digital VTR, a television receiver, a communication terminal, and the like can be used.

[0061]

According to the first aspect of the present invention, in an electronic device incorporating a speaker to which an audio signal is supplied, a digital signal for controlling a digitized audio signal of the audio signal to a predetermined characteristic according to the characteristic of the speaker. Set up a signal processor,
Since the digitized audio signal obtained from the digital signal processor is converted into an analog signal and supplied to the speaker, the sound quality of the speaker can be improved.
An electronic device with a built-in speaker can be obtained. When the speaker is a large speaker, the sound quality can be further improved. When the speaker is a small speaker, the poor sound quality can be improved.

According to the second aspect of the present invention, in a portable electronic device incorporating a small speaker to which an audio signal is supplied,
Digitized audio signal A digital signal processor for controlling the audio signal to a predetermined characteristic according to the characteristics of the small speaker is provided, and the digitized audio signal obtained from the digital signal processor is converted into an analog signal and supplied to the small speaker. As a result, it is possible to obtain a portable electronic device having a built-in small speaker, which can improve poor sound quality of the small speaker.

According to the third aspect of the present invention, in a portable electronic device incorporating the small loudspeaker of the second aspect of the present invention, the control of the predetermined characteristic is automatic gain control. And a portable electronic device with a built-in small loudspeaker, which has the effect of increasing volume or reducing noise.

According to a fourth aspect of the present invention, in a portable electronic device incorporating the small loudspeaker of the third aspect of the present invention, automatic gain control is performed when the absolute value of the level of the input digital audio signal is less than a predetermined level. An output digital audio signal whose level has been expanded is obtained, and when the output digital audio signal exceeds a predetermined level, a level-compressed output digital audio signal is obtained. A portable electronic device having a built-in speaker can be obtained.

According to the fifth aspect of the present invention, in a portable electronic device incorporating the small loudspeaker of the third aspect of the present invention, automatic gain control is performed when the absolute value of the level of the input digital audio signal is higher than a predetermined level. A level-compressed output digital audio signal is obtained. When the level exceeds a predetermined level, an output digital audio signal having the same level as the input digital audio signal or a level-expanded output digital audio signal is obtained. A portable electronic device with a built-in small speaker, which has the same effect and has a noise reduction effect, can be obtained.

According to the sixth aspect of the present invention, in the portable electronic device incorporating the small speaker according to the fourth aspect of the present invention, the automatic gain control means sets A [n] to n-sample attenuation coefficient, Ak
When (Ak>Ak> 1) is used as a level-up coefficient, an operation of P × A [n] × Ak≡M is performed on the input digital audio signal P, and as a result of the operation, an n-sample monaural digital signal is obtained. The first arithmetic means for obtaining the audio signal M and the second arithmetic means for obtaining the | S | by converting the arithmetic result of the first arithmetic means into an absolute value as | P × A [n] × Ak | ≡ | S | Calculation means and T
When / H (where T / H> 0) is a threshold coefficient, first comparing means for comparing whether | S | is | S |> T / H, and the first comparing means When the comparison result of the means is | S |> T / H, Ka
(Where Ka is Ka ≦ 1) as an attack coefficient, the dynamic range is compressed by performing the calculation of A [n] × Ka → A [n + 1], and (n +
1) When the comparison result of the third calculation means for obtaining the sample attenuation coefficient A [n + 1] and the first comparison means is | S | ≤T / H, Kc is a recovery counter coefficient and α is an increment. At this time, a first recovery counter coefficient Kc is obtained as Kc + α → Kc.
And Kr as a recovery coefficient after counting by the first counter means and the second comparing means for comparing whether or not the recovery counter coefficient Kc satisfies Kr> Kc. When the comparison result of the second comparison means satisfies Kr> Kc, the operation of A [n] → A [n + 1] is performed, and the (n + 1) sample attenuation coefficient A [n +
1], the result of the comparison between the fourth calculating means and the second comparing means is Kr ≦ Kc, the recovery counter coefficient K
A fifth calculating means for setting c to Kc = 0, and after calculating by the fifth calculating means, A [n] + α → A [n + 1] is obtained to obtain (n + 1) sample attenuation coefficient A [n + 1]. A third calculating means, a fourth calculating means,
(N +) obtained from the calculating means or the second counter means.
1) Using a sample attenuation coefficient A [n + 1], a first calculating means, a second calculating means, a first comparing means, a third calculating means, a first counter means, a second comparing means, In the arithmetic means 4, the fifth arithmetic means and the second counter means, (n + 1) is substituted for each n, and (n + 1)
Since the sample operation is performed, the same effect as that of the fourth aspect of the present invention is obtained, and the level of the audio signal obtained by multiplying the input digital audio signal by the level-up coefficient is compared with a threshold coefficient T / H. When the threshold coefficient T / H is larger than the threshold coefficient T / H, the level is multiplied by the attack coefficient Ka to compress the level. When the threshold coefficient T / H is smaller than the threshold coefficient T / H, the level is gradually expanded using the attack coefficient and the recovery coefficient. Therefore, it is possible to obtain a portable electronic device that incorporates a small speaker that does not cause distortion in a signal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a flowchart illustrating a process of AGC performed by the digital signal processor according to the embodiment of the present invention.

FIG. 4 is a characteristic curve diagram showing input / output characteristics in the case of the AGC of FIG.

FIG. 5 is a characteristic curve diagram showing input / output characteristics in the case of another AGC.

FIG. 6 is a waveform diagram showing a comparison of input / output signal waveforms in the case of the AGC of FIG. 5; A Waveform of input signal B Waveform of output signal

FIG. 7 is a characteristic curve diagram and a waveform diagram showing input / output characteristics and a waveform of an input / output signal in still another AGC. A Input / output characteristics B Input signal C Output signal

FIG. 8 is a characteristic curve diagram and a waveform diagram showing input / output characteristics and waveforms of input / output signals in still another AGC. A Input / output characteristics B Input signal C Output signal

[Explanation of symbols]

4 A / D converter, 8 DSP, 9 Characteristic control means, 1
0, 11 D / A converter, 12, 13 Low frequency amplifier, 14 line output terminal, 15 speaker.

Claims (6)

[Claims] 1. An electronic device incorporating a speaker to which an audio signal is supplied, comprising: a digital signal processor for controlling a digitized audio signal of the audio signal to a predetermined characteristic according to the characteristic of the speaker; An electronic device having a built-in speaker, wherein a digitized audio signal obtained from a signal processor is converted into an analog signal and supplied to the speaker. 2. A portable electronic device having a built-in small speaker to which an audio signal is supplied, comprising: a digital signal processor that controls a digitized audio signal of the audio signal to a predetermined characteristic according to the characteristic of the small speaker. A portable electronic device having a built-in small speaker, wherein the digitalized audio signal obtained by the digital signal processor is converted into an analog signal and supplied to the small speaker. 3. A portable electronic device having a built-in small speaker according to claim 2, wherein the control of the predetermined characteristic is an automatic gain control. 4. The portable electronic device having a built-in small speaker according to claim 3, wherein the automatic gain control is performed when the absolute value of the level of the input digital audio signal is equal to or less than a predetermined level. A portable electronic device having a built-in small speaker, wherein an audio signal is obtained and an output digital audio signal whose level is compressed when the level exceeds the predetermined level is obtained. 5. The portable electronic device incorporating a small speaker according to claim 3, wherein the automatic gain control is performed when the absolute value of the level of the input digital audio signal is equal to or greater than a predetermined level. A portable electronic device having a built-in miniature speaker, wherein an audio signal is obtained, and when the level exceeds the predetermined level, an output digital audio signal having the same level as the input digital audio signal or having an extended level is obtained. 6. The portable electronic device having a built-in small speaker according to claim 4, wherein the automatic gain control means comprises: A [n] is an n-sample attenuation coefficient, and Ak (where Ak is A
When k> 1) is a level-up coefficient, an operation of P × A [n] × Ak≡M is performed on the input digital audio signal P, and an n-sample monaural digital audio signal M is obtained as the operation result. A first calculating means; and a second calculating means for obtaining an | S | by converting an operation result of the first calculating means into an absolute value as | P × A [n] × Ak | ≡ | S | When T / H (where T / H is T / H> 0) is used as a threshold coefficient, first comparing means for comparing whether or not | S | is | S |> T / H When the comparison result of the first comparing means is | S |> T / H, when Ka (where Ka is Ka ≦ 1) is used as an attack coefficient, A [n] × Ka → A [n + 1 ] To reduce the dynamic range, and (n +
1) When the comparison result of the third calculation means for obtaining the sample attenuation coefficient A [n + 1] and the first comparison means is | S | ≦ T / H, Kc is a recovery counter coefficient, and α is an increment. In this case, a first recovery counter coefficient Kc is obtained as Kc + α → Kc.
When Kr is a recovery coefficient after counting by the first counter means, the recovery counter coefficient Kc
Is compared with Kr> Kc. When the comparison result of the second comparison means is Kr> Kc, the operation of A [n] → A [n + 1] is performed. Then, the (n + 1) sample attenuation coefficient A [n +
1], a fifth calculating means for setting the recovery counter coefficient Kc to Kc = 0 when the result of comparison of the second comparing means is Kr ≦ Kc, After the operation of the arithmetic means, there is provided second counter means for obtaining (n + 1) sample attenuation coefficient A [n + 1] as A [n] + α → A [n + 1]. Using the (n + 1) sample attenuation coefficient A [n + 1] obtained from the second calculating means or the second counter means, the first calculating means, the second calculating means, and the first comparing means. In the third calculating means, the first counter means, the second comparing means, the fourth calculating means, the fifth calculating means and the second counter means, each of the n is (n + 1) ), And perform the operation of (n + 1) samples, respectively. Portable electronic device having a built-in miniature loudspeaker, characterized in that cause I.