JPS6110182Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a device for measuring the transient characteristics of a transmission system, particularly the reverberation characteristics.

In general, it is often necessary to carry out targeted characteristic measurements in order to learn various characteristics of a particular acoustic room from an acoustic point of view. For example, when a lecture is given in a single hall or a musical performance is performed by a band, the acoustic effects of the speech or music become important. In this case, if matters such as the short sound attenuation characteristic of a signal from a single signal source or the reverberation time are clearly understood, the structure of the venue where the event will be held or the acoustics Due to its characteristics, it is possible to aim for high acoustic effects.

Among various acoustic characteristics, for example, transient characteristics, especially the reverberation (attenuation) curve necessary to calculate the reverberation time of a room, can be measured by measuring the sound receiving point when stationary band noise is cut off. There are ways to measure attenuation characteristics. However, in such a method, the accuracy of measuring reverberation time is limited by random changes in the decay curve (transient curve). To minimize the effect of variations in the decay curve on the measured reverberation time values, it is necessary to repeat and average the reverberation measurements many times. However, this method is not only inefficient, but also does not provide the true characteristics of the damping, ie, the essential transient response curve of the system to stationary noise.

By the way, as a method to measure transient characteristics,
MR Schroeder's so-called impulse response square integration method is known. The principle is that when the sound source band noise is cut off from the steady state, the essential transient response characteristic <S ² (t)> corresponding to the average of ∞ times of the reverberation decay curve, for example, is calculated from the sound source. - It is to be determined from the impulse response r(x) between sound receiving points, and according to this, the sound pressure level S(t) at a certain time t of the transient characteristic is expressed as follows.

<S ² (t)>=N∫ ^∞ _t r ² (x) dx ...(1) where N: power of sound source band noise, r
(x): Impulse response.

Therefore, by squaring and integrating the impulse response r(x) in the integration interval [t, +∞], the collective average of the infinite number of squares of the sound pressure level S(t) at time t can be found. . Methods of actually obtaining the transient characteristics of a certain chamber, such as a reverberation curve, based on the above principle can be roughly divided into the following two methods. (1) is the so-called double impulse method, and (2) is the so-called backward integration method.

The principle of the double impulse method (1) is carried out by expanding the principle equation (1) above as follows.

<S ² (t)>=N∫ ^∞ _t r ² (x) dx = N∫ ^∞ _t r ² (x) dx−N∫ ^t _p r ² (x) dx ...(2) Here, the integral interval [ Obtain the square integral of the impulse response r(x) for [o, +∞] first, and then sequentially subtract the square integral of the impulse response r(x) for the integral interval [o, t] that changes from moment to moment. By doing so, the transient characteristics <
S ² (t)> is obtained.

FIG. 1 shows the configuration of a conventional device for measuring reverberation characteristics according to this principle.

In this figure, an impulse signal from an impulse source 2 (e.g. a paper pistol) is
Pick up the second impulse with microphone 3,
After the output is sent to the squaring circuit 4 and squared, it is sent to the integrating circuit 6 via the switch SW, where the signal is integrated and displayed on the display device 7. When generating the second impulse, change the switch SW to connect it to the inverting circuit 5 to invert it, and then connect it to the inverting circuit 6.
If the output is displayed through the , a transient characteristic such as a reverberation curve can be obtained as a process of subtracting the latter from the former.

However, in this double impulse method, it is necessary to generate two identical pulses with high accuracy as a sound source, or to use a tape recorder etc. to generate two identical pulses.
It is technically almost impossible to reproduce the impulse response of the first time exactly the same as the first time. Therefore, since the shapes of the generated impulses are different, there is a drawback that the measurement error becomes large especially at the end of the integration, that is, at the point at the end of the reverberation curve where the level is small.

In addition ^, the principle of _the backward integration ^method in ( ^{2 ) is} as follows _: −x)dx ......(3), it is obtained by integrating in the opposite direction. In other words, the integral interval [t, ∞] is changed to [−
∞, -t] to obtain the transient characteristic <S ² (t)>.

FIG. 2 shows the configuration of a conventional device for implementing this method.

In this figure, first, the impulse response r(x) from the picked-up microphone is once recorded on a tape recorder 4', and then the tape recorder 4' is reversed to reproduce the impulse response in reverse, and the output is The signal is supplied to a display device 7' via a squaring circuit 5' and an integrating circuit 6'. However, this method has the disadvantage that it cannot perform real-time processing because the collected impulse response is recorded once on a tape recorder, etc., and also requires a tape recorder, etc. to memorize the impulse response r(x) itself. There is a drawback that. Therefore, it lacks immediacy.

From the above point of view, the purpose of this invention is to provide a device that can measure transient characteristics, such as reverberation decay curves, with high precision in real time using a single impulse, such as a tone burst wave, without repeating reverberation measurements. purpose.

Another object of this invention is to provide an apparatus for measuring the transient characteristics of a transmission system, which can display in real time the transient characteristics of the transmission system that change from time to time using a single impulse.

Furthermore, another purpose of this invention is to display the calculation results during the calculation to measure the transient characteristics of the transmission system, and to display the shape of the attenuation curve that changes from time to time from the initial characteristics to the final characteristics of the transient characteristics. is displayed in real time, and when displaying, the starting point level is always kept constant, and the result is displayed in parallel with the impulse response r(x) in a way that makes it easy to compare the progress of the return. The object of the present invention is to provide a device for displaying information.

In order to achieve the above objectives, the device according to this invention converts the collected impulse response r(x) into a digital signal in a device that analyzes the impulse response r(x) and measures the transient characteristics of the transmission system. an analog/digital converter that squares the digital signal from this converter, and a device that repeatedly accumulates the output of this device to obtain a large number of integration intervals [o, ti (i = 0, 1, 2,...T )]; a _first storage device that sequentially stores the integral values from ^{the accumulator} ; A second storage means that temporarily stores only the integral value ∫ ^ti _p r ² (x) dx, and each storage content of the first storage device and the storage content of the second storage means are read out and ∫ ^ti _p
r ² (x)dx−∫ ^{ti−1, ti−2,} … ^o _p r ² (x)dx
and a subtraction device for subtracting each of these subtraction results, and a level shift is performed for each of these subtraction results by the value obtained by subtracting the integral value ∫ ^ti _p r ² (x) dx of the latest time point ti from a predetermined value corresponding to the display starting point level α. It is characterized by comprising a level shift device and a device that sequentially displays/records the transient characteristics of the calculated results over time.

Next, an embodiment of this invention will be described with reference to the drawings.

FIG. 3 shows the configuration of an apparatus implementing this invention. The chamber 11 is a room in which transient characteristics, for example, reverberation characteristics, are to be measured, and a sound source 12 that generates impulses is provided therein. This impulse source may be, for example, a paper pistol. Reference numeral 13 indicates a microphone as a sound collection device, which receives an impulse response r(x) from the sound source 12. This collected impulse response r(x) is amplified by an amplifier 14 and then converted to an analog/digital converter (hereinafter referred to as A/D).
It is abbreviated as a converter. ) 15 converts the analog signal into a digital signal.

The digital signal representing the impulse response r(x) converted in this way is sent to the square circuit 1.
6 and its output is sent to an accumulator 17. This accumulator 1
7, different integral intervals [o, ti (i=0,
1, 2, ...T)], the squared output from the square circuit 16 is repeatedly accumulated to perform integration (cumulative addition) corresponding to the integral of ∫ ^ti _p r ² (x) dx, and the result is The integral value is temporarily stored in a random access memory (hereinafter referred to as RAM) 18 as a first storage device and a register 19 as a second storage device.

That is, in this case, the RAM 18 stores the respective integral values in the integral interval [o to ti] calculated by the accumulator 17 ∫ ^{ti (i=1, 2, 3,} ... ^T) _p r ² (x) dx ……(Four
) are stored at a certain sampling period. On the other hand, in the temporary storage register 19, among the integral values that are updated every moment, the final value at the time ti ∫ ^{last ti} _p r ² (x) dx ...(5) is temporarily stored. . Writing to RAM 18 and reading from RAM 18 are performed at appropriate time intervals by timing pulses from timing control device 21. In particular, RAM1
When reading the integral value data stored in 8, the period of the read pulse issued from the timing control device 21 is made shorter than the period of the write pulse used during writing (storage). That is, the period of the read pulse is sufficiently shorter than the period of the write pulse by 1/n times the reciprocal, where n is the number of data stored in the RAM 18.

By doing so, the transient characteristics of the transmission system to be measured, including the progress thereof, can be displayed on the display device from time to time.

Now, as described above, the integral value data represented by equation (4) stored in the RAM 18 is read out at the read timing and applied to one input of the subtracter 20. On the other hand, the final integral value data stored in the register 19 at the time point ti expressed by equation (5) is also read out by the read pulse from the timing control device 21 and input to the other input of the subtracter 20. Given. In this way, the subtracter 20 performs subtraction between the two types of integral data supplied to the subtracter 20. That is, in the subtracter 20, ∫ ^{last ti} _p r ² (x)dx
−∫ ^{ti (i=1, 2,} . . . ^T) _p r ² (x) dx is calculated.

This result is not passed through the level shift device 22, but is directly sent to a read-only memory (hereinafter referred to as ROM) 23, which is a logarithmic compressor (a table for converting input data into logarithmic data), and the above calculation result is Interface 24 after logarithmic compression
It can also be displayed on the display device 25 via.

FIG. 4 shows the transient characteristics displayed on the display device 25 without passing through the level shift device 22 as described above. In contrast to the amplified waveform of the signal received by the microphone 13 as shown in a of the same figure, b shows the output signal repeatedly and cumulatively integrated by the accumulator 17 in analog form. ,2,3,
... Each point T _-2 , T _-1 , T indicates a waveform stored in the RAM 18 at a certain sampling period determined by the period of the write timing pulse of the timing control device 21 among the integrated waveforms shown by the solid line. There is. In Fig. 4, c shows the transient characteristics <S ² (t)> of the transmission system measured from t=o when the impulse is generated to a certain final time T, and d shows the transient characteristics of the transmission system measured in the ROM 23. Logarithmically compressed 10log<S ² (t)
The process in which the characteristics of In addition, in c and d of the same figure, t=
0, t = 1, t = 2, t = 3, ... For convenience, the transient characteristics at the time of t = T are shown all at once on the drawing, but in reality, they are shown at the time when each integration is completed. So, the characteristic of t=1, the characteristic of t=2, t=3,...
In this way, the transient characteristics that change from moment to moment are drawn one by one.

However, in this case, as shown in Figure 4c and d, the starting point of t=o is not constant and the starting point level of the reverberation waveform is moving, making it difficult to see the characteristics of the display surface, and furthermore, the final waveform Since <S ² (t)> corresponds to the average of the reverberant waveform when steady-state band noise is cut off, its progress does not tend to match the actual situation. Therefore, in this invention, in consideration of this problem, all starting point levels are shifted and clamped to the starting point level of the characteristic at the final point, and the reverberation waveform when the stationary band noise is cut off is obtained simultaneously. Therefore, a level shift device 22 is provided after the subtracter 20 to keep the starting point level constant. By this level shift device 22, the starting point level α is always kept constant, and the impulse response r
In accordance with the analysis of (x), in parallel with this, transient characteristics are displayed moment by moment in the same manner as the waveform caused by the band noise described above.

The level shift amount Ai of the level shift device 22 at time ti is calculated as follows. The transient characteristic <S ² (t)> is <S ² (t)>=∫ ^T _ti r ² (x) dx = ∫ ^T _p r ² (x) dx−∫ ^ti _p r ² (x) dx (where i=0, 1, 2,...n), ti
The shift amount Ai at the time is Ai = α−S ² i (where α is the starting point reference level of the reverberation curve and is the value integrated from 0 to T, S ² i: ∫ ^ti _p r ² (x) dx) This is the value expressed as .

FIG. 5 shows the characteristics of <S ² (t)> as a result of shifting by this level shift device 22. A in FIG. 5 shows S ² i in FIG. 4 shifted by Ai. That is, for example, in FIG. 4, the transient characteristic at t=1 is shifted by _A1 to match the level of the starting point of the transient characteristic at the final value of t=T. Fig. 5b shows the characteristic of Fig. 4 t=2 shifted by A ₂ , and Fig. 5c shows the characteristic of Fig. 4 t=3 shifted by A2.
It is shown that it is shifted by A ₃ and moved to the starting point of the characteristic at t=T. Thus, FIG. 5g shows the transient characteristic in which the final value t=T has been reached.

FIG. 6 shows the shifted data according to the present invention which has been logarithmically compressed via the ROM 23 as a logarithmic compressor.
The characteristics of 10log<S ² i(t)> are shown. In other words, Fig. 6a shows 10log in the characteristic of t=1 in Fig. 4.
The graph shows a state where <S ² (1)> is shifted by A ₁ =α−S ² (1) to match the starting point level of the characteristic at t=T. That is, the characteristic at t=1 in FIG. 4 is expressed as <S ² (1)>=10log<S ² (1)>+A ₁ .

Figure 6b shows the characteristic of t=ti in Figure 4.
10log<S ² (i)> is shifted by Ai=α−S ² (i) to match the starting point level of the characteristic at t=T.

FIG. 6c depicts the transient characteristics at the time when the final level of t=T is calculated. In this case, there is no level shift.

As described above, in this invention, for the output of the subtraction device 20, for each transient characteristic at an arbitrary time point to be displayed, the starting point level of each of the above transient characteristics is set to the starting point level at the final time point t=T. By matching the values, the transient characteristics are displayed in real time in a format that makes it easy to compare.

Note that when displaying transient characteristics, at any intermediate integration point ti, the integration of the integration interval [ti, T] has not yet been completed, so it may differ slightly from the final reverberation curve as shown in Figure 6. However, in practice, the error is small, and the transient characteristics at the time of final integration up to [0, T] are correct as shown in Figure 6c or Figure 5g. is found.

In the above embodiment, the level shift device 2
2 is arranged before the ROM 23 as a logarithmic compression device, but the effect remains the same even if the same level shift device is arranged after the ROM 23.

As mentioned above, in this invention, by matching the starting point level of the transient characteristic at each time point with the starting point level of the transient characteristic at the final integration time, the reverberant waveform is made easier to see, and the product effectiveness of the transient characteristic measuring device is increased. be able to.

[Brief explanation of the drawing]

Fig. 1 shows a diagram explaining the double impulse method according to the prior art and its waveform, Fig. 2 shows a system diagram explaining the backward integral method according to the prior art and its waveform, and Fig. 3 shows the transmission according to this invention. An example of the device for measuring the transient characteristics of the system is shown, and the fourth
The figure shows the waveform passed through the square circuit of the apparatus of figure 3, the output waveform of the accumulator, and the waveform displayed on the display device without passing through the level shifter, and figures 5 and 6 show this waveform. FIG. 6 shows a transition diagram of transient characteristics displayed when a level shift device according to an embodiment of the invention is provided. 11...Chamber, 12...Sound source, 13...
Microphone, 15...A/D converter, 16...
...Squaring device, 17...Accumulating device (accumulator), 18...First storage device (RAM), 19...
... Second storage device (register), 20 ... Subtraction device, 21 ... Timing control device, 22 ... Level shift device, 23 ... Read only memory, 2
4...Interface, 25...Display device.

Claims (1)

[Claims for Utility Model Registration] An analog/digital conversion device that converts the collected impulse response r(x) into a digital signal in a device that analyzes the impulse response r(x) to measure the transient characteristics of a transmission system. , a device for digitally squaring the digital signal from this conversion device, and a device for digitally repeatedly accumulating the squared output of this device to obtain a large number of integration intervals [o, ti (i=0, 1, 2,...
an accumulating device that calculates the square integral value ∫ ^ti _p r ² (x) dx at [T)]; a first storage device that sequentially stores the integral values obtained from the accumulating device; a second storage device that temporarily stores only the integral value ∫ ^ti _p r ² (x)dx at the latest time point ti; Each of the latest memory contents stored in the storage means is read out and ∫ ^ti _p r ² (x) dx−∫ ^{ti-1, ti-2} … ^o _p r ²
(x) dx, and for each of these subtraction results, the integral value ∫ ^ti _p r ² (x) dx from the predetermined value corresponding to the display starting point level α to the latest time point ti.
and a device for displaying or recording the level-shifted subtraction result levels in correspondence with the time axis. , the transient characteristics of the transmission system over time,
An apparatus for measuring transient characteristics of a transmission system, characterized in that the display or recording is performed so that the display start level position of each characteristic always becomes the level value α.