JP3462390B2 - Volume indicator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a volume indicating device for instructing the volume (loudness level, loudness, effective value or VU value, etc.) of the sound of a television or radio program.

[0002]

2. Description of the Related Art For volume, VU value specified by BTS5703, loudness, loudness level, sound pressure level specified by JISZ8106 acoustic term (general),
There is an effective value in addition to the noise level.

Although a VU meter is one of the volume indicating devices, the indicated value of the VU meter changes rapidly with respect to a voice signal which changes from moment to moment. The indicated value (VU value) of the VU meter is "the level is indicated by an instruction that the peak fluctuations that often appear are at the fingertips or slightly exceed them (Broadcasting Technology Shubo 3, Broadcast Sound Technology, edited by Japan Broadcasting Corporation, Nippon Broadcasting System). Publishing Association, 1982, p.135) ", so there is a drawback that the reading error is large due to differences in people. As can be seen from how to read the VU value, in the VU meter or the like, the indication value of a low level portion such as a silent section is not important, but the indication value of a large level portion is important.

[0004]

As described above, there is a VU meter or the like as a device for displaying the volume of an audio signal.
Since the indicated value changes rapidly in accordance with the volume that changes from moment to moment, there is a drawback in that the reading error due to the difference between people becomes large. It is possible to delay the change in the indicated value by increasing the time constant of the indicating circuit, that is, by calculating the long-term average value, but the larger the time constant, the slower the rising speed of the indicated value may be. However, in the case of narration, there is a drawback that the indicated value becomes smaller on average due to the influence of a silent section such as a breathing section.

Some peak meters hold the peak value and display it to make it easier to read the peak level. However, the held peak value does not change continuously but increases with each hold time. It had the drawback of changing.

Therefore, an object of the present invention is to eliminate the above-mentioned various drawbacks, to gently change the indicated value, to reduce the reading error due to the difference of persons, to prevent the indicated value from becoming small due to the influence of a silent section, etc. It is intended to provide a sound volume indicating device that shows a specified indication value in a short time for a typical audio signal.

[0007]

In order to achieve this object, the volume indicator of the present invention comprises means for sequentially dividing input audio signals into blocks so as to overlap each other temporally or not to overlap each other. Of the values calculated by the means for calculating the volume of the audio signal for each block divided by the dividing means and the value calculated by the means for calculating the volume, up to the past nth block counted from the current time And a means for sequentially calculating the average value calculated by the means for calculating the average value.
And m are positive integers, and n> m.

Further, in the volume indicator of the present invention, the volume of the audio signal is the loudness level, the loudness, the effective value, V
It is characterized by a U value, a noise level, or a sound pressure level.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be sequentially described in detail below. In the configuration of the present invention, the input audio signal is first divided into blocks. When displaying the loudness level, loudness, or noise level, it is good to divide them into sequential blocks so that they overlap each other in time, but when displaying the effective value, VU value, or sound pressure level, do not overlap each other in time. You may divide into.

Next, the volume of the audio signal is calculated for each of the divided blocks. When the loudness level or loudness is calculated, FFT (Fast Fourier Transform) is performed after multiplying each divided block by a window function (window) such as Hanning or Hamming, and ISO 532 (Acoustics-Method) is used by using the result. for calculatin
(G loudness level) standardized by Zwicker et al. (Program for calculating loudness according to D
IN45631 (ISO 532B), J. Acoust. Soc. Jpn (E), pp.39〜
42. Vol.12, No.1, 1991) or the method of Moore et al. (AMo
del for the Prediction of Thresholds, Loudness, an
d Partial Loudness, J. Audio Eng, Soc., pp.224〜239,
Vol.45, No.4, 1997 April).

The method of Zwicker et al. Is standardized as the method of ISO532, but the loudness level (unit: ph
The algorithm for calculating on) or loudness (unit: sone) is as follows.

In order to calculate the loudness level or loudness, the characteristics of human hearing are faithfully simulated as shown in FIG. It is thought that human hearing uses frequency analysis at the basilar membrane of the cochlea and performs analysis for each of multiple bands.Therefore, even when calculating the loudness level or loudness, the audio signal is divided into multiple bands by the bandpass filter. Split into. Next, effective value detection and integration are performed to correct the frequency level characteristic. The frequency level characteristic is determined based on the equisensitivity curve of the sound (a curve with a constant loudness). The dB conversion is performed for each band, that is, the sound pressure level is obtained, and then the sound pressure level is converted. The relationship between the sound pressure level and the loudness of each band has been previously obtained by psychological experiments. Next, the loudness reduction is calculated by masking the neighboring components, and finally, the loudness is added for all bands to calculate the loudness. The relationship between loudness (S) and loudness level (L) has been clarified by psychological experiments. For example, S is about 1 (s
One) or more, there is a relation of log ₁₀ S ≈0.03 (L-40). When calculating the loudness level,
Sone / phon conversion is performed using the relationship between loudness (S) and loudness level (L).

The method of calculating the effective value, VU value, noise level or sound pressure level for each block is well known. After the volume of each block is calculated by the above method, the average value of the m values (n ≧ m) up to the nth value in the past counting from the current time And calculate the average value. n
The larger the value of, the longer the silent section can be eliminated, so the change in the indicated value can be made more gradual.
If is too large, a non-zero indication value is indicated for a long time even if the silent section continues for a long time, so it is necessary to set the length appropriately. Further, the larger the value of m, the more gradual the change of the indicated value, but the rise time of the indicated value becomes slower. Therefore, it is necessary to reduce m to some extent to shorten the rise time of the indicated value. In the above method, 1
Since the new instruction value is updated for each block, the amount of change in the instruction value is small and the instruction value changes gently.

Further, the longer the block length is, the slower the rising of the indicated value is, and the longer it takes to update the indicated value, so that the change amount of the indicated value becomes large. Therefore, it is necessary to shorten the block length to some extent.

In a volume indicating device such as a VU meter, the indication value of a low level portion such as a silent section is not so important, and the indication value of a large level portion is important. Also, a loudness level or loudness is an important part for how to hear a sound, and a large sound level. Therefore, among the values calculated for each block, the average value of the m values (n ≧ m) up to the n largest value among the past n values counted from the current time is calculated. Calculate and ask for the average value. Since the instruction value is calculated using only a large value, the instruction value does not averagely decrease as in the case of simply averaging for a long time.

When the volume indicator according to the present invention is processed with a digital signal, the following can be done.
The input audio signal is converted into a digital signal with a sampling frequency of 48 kHz and a quantization of 16 bits, for example.
It is necessary to set the block length to an appropriate length, but FF
To facilitate T (frequency analysis), for example, 204
Divide every 8 samples. When the blocks are divided so as to overlap each other temporally, for example, 1024
Move the blocks of division so that the samples overlap. That is, a total of 2048 samples of the latter half 1024 samples of the immediately preceding block and the next 1024 samples are set as the next divided block.

When multiplying a window function (window) of Hanning or Hamming, for example, Sei Imai (Digital Signal Processing, Industry News Publication, Electronic Science Series 88 (1980),
Perform calculations according to p.55 to p.66). The Hanning window w (n) for N sample data is w (n) = 0.5 (1−cos (2πn / N)), where n = 0,
Since it is given by 1, 2, 3, ---, (N-1), for example, w (n) = 0.5 (1-cos (2πn / 2048)) for 2048 sample data, where n = 0,
Multiply by 1, 2, 3, ---, 2047. The Hamming window w (n) for N sample data is w (n) = 0.54−0.46cos (2πn / N), where n = 0,
Since it is given by 1, 2, 3, ---, (N-1), for example, w (n) = 0.54-0.46 cos (2πn / 2048) for 2048 sample data, where n = 0 ,
Multiply by 1, 2, 3, ---, 2047.

After dividing into blocks, the volume is calculated by the above-mentioned method or the like. In the instruction section, for example, n = 1
The indicated value is calculated with 00, m = 10. The time difference between blocks is 1024 sample times, or 21.33
Since ms (= 1024/48000), the time for 100 blocks corresponds to 2.133 seconds. That is, n = 100, m =
In the case of 10, 10 blocks having a large value within 2.133 seconds (not necessarily 10 blocks that are continuous in time), that is, an average value for 213.3 ms are calculated.

The loudness of sound is influenced by the duration, and becomes maximum when the duration is about 300 ms (Hearing and Psychoacoustics, edited by Hisao Sakai, Corona Publishing Co. (1978), p.165). Therefore, when displaying the loudness level or loudness, it is preferable to set m = about 10 to 20. Since the indicator value obtained by the above method changes gently, it is already easy to read, but if the peak value of the indicator value is held and displayed, the indicator device becomes easier to read.

[0020]

Embodiments of the present invention will now be described more specifically with reference to the accompanying drawings. In the drawings, constituent blocks having the same function are designated by the same reference numerals. FIG. 1 shows an example of the principle of the present invention. The input audio signal is sequentially divided into blocks by the configuration block 1, and the volume of each block is calculated by the configuration block 2. Next, in the configuration block 3, the average value of m values (where n ≧ m) is calculated in order from the largest value among the past n values counted from the current time,
The average value is sequentially displayed in the configuration block 4.

FIG. 2 shows an example of the principle of the present invention with peak display. In addition to the display value shown in FIG. 1, the peak value is detected by the constituent block 5 and displayed simultaneously by the constituent block 4.

FIG. 3 shows an example of a concrete configuration that is convenient for carrying out the present invention. The input voice is converted into a digital signal in the configuration block 6, and a DSP (Digital Signal) dedicated for voice is used.
The algorithm of the present invention can be easily realized by using the Processor 7. The DSP is a well-known high-speed microprocessor that performs multipurpose signal processing (for example, NH
K Broadcasting Research Laboratories "Digital Encyclopedia of Multimedia in the Age of Multimedia" Maruzen Co., Ltd. (1994), p.296-p.29
7).

FIG. 4 is a block diagram showing an algorithm in the DSP for displaying the loudness level or loudness. The digital voice data is sequentially divided by the constituent block 1, multiplied by the window function 8 and FFT 9 is performed.
Next, after the loudness level or loudness is calculated 2, the indicated value is calculated 3.

FIG. 5 is a block diagram showing an algorithm in the DSP for displaying the effective value or the VU value. The digital voice data is sequentially divided by the constituent block 1, the effective value or the VU value is calculated, and then the instruction value is calculated.

Although the embodiments of the present invention have been described with reference to some examples, the present invention is not limited to these, and various modifications and changes can be made within the scope of the invention defined in the claims. What is possible is self-evident.

[0026]

According to the present invention, a volume indicating device with a small reading error can be realized. In addition to displaying the loudness level or loudness, it is possible not only to objectively reduce variations in loudness between programs, but also to objectively set appropriate level balance between narration and BGM (back ground music). You will be able to do it.

[Brief description of drawings]

FIG. 1 shows an example of the principle configuration of the present invention.

FIG. 2 shows an example of the principle configuration of the present invention with peak display.

FIG. 3 shows a specific configuration example of a DSP of the present invention.

FIG. 4 shows a block diagram of a DSP algorithm for displaying a loudness level or loudness.

FIG. 5 shows a block diagram of a DSP algorithm when an effective value or a VU value is displayed (when a window function is not applied).

FIG. 6 shows a block diagram simulating human hearing to calculate loudness or loudness level.

[Explanation of symbols]

1 block division 2 Volume calculation 3 Calculation of indicated value 4 display 5 peak detection 6 A / D conversion 7 DSP 8 Window function 9 FFT

Continuation of front page (56) Reference JP-A-5-240698 (JP, A) JP-A-6-36460 (JP, A) JP-A-2-47698 (JP, A) JP-A-5-323996 (JP , A) JP 8-145778 (JP, A) JP 9-152894 (JP, A) JP 10-253440 (JP, A) JP 11-73193 (JP, A) JP 56-125634 (JP, A) JP-A-60-117296 (JP, A) JP-A-63-250530 (JP, A) Actual development Sho-56-26978 (JP, U) Recent movement, Journal of Acoustical Society of Japan, May 1, 1990, Vol. 46 No. 5, pp. 427-432 Kenji Ozawa, Yoichi Suzuki, Toshio Sone, Shunichi Kano, Shunichi Chiba, Jiro Soma, Consideration on characteristic design of loudness circuit based on preservation condition of masked spectrum, Journal of Acoustical Society of Japan, 1990, Vol. 46 No. 9, pp. 736-746 (58) Fields investigated (Int.Cl. ⁷ , DB name) G01H 3/00-3/14 G10L 11/00-11/06

Claims (2)

(57) [Claims] 1. A unit for sequentially dividing an input audio signal into blocks so as to overlap each other temporally or not so as to overlap each other, and a unit for calculating the volume of an audio signal for each block divided by the dividing unit. Then, after the value calculated by the means for calculating the volume, the average value of the values up to the m-th block in the order of the past n-th block counted from the current time is calculated. A volume indicating device comprising: a means for calculating and a means for sequentially displaying the average values calculated by the means for calculating the average value, wherein n and m are positive integers and n> m. 2. The volume indicating device according to claim 1, wherein the volume of the audio signal is a loudness level, a loudness, an effective value, a VU value, a noise level or a sound pressure level.