JPS6113171B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method and apparatus for displaying or recording transient characteristics of a transmission system. 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 the attenuation characteristics for the signal from one signal source or the reverberation time are clearly understood, the structure of the venue where the event will be held and the acoustic characteristics This means that you can aim for high acoustic effects. Among various acoustic characteristics, several methods have been considered in the past for measuring transient characteristics or attenuation characteristics, including, for example, reverberation time characteristics. One method is to measure the reverberation time by exciting the room using a tone burst wave and integrating the impulse response of the tone burst wave, but the accuracy with which the reverberation time can be determined from the decay curve is The decay curve (transient curve) was limited by random changes. One way to minimize the effect of attenuation curve variations on measured reverberation time values is to repeat the reverberation experiment many times and take the average. However, this method is not only inefficient, but also does not reveal the true characteristics of the attenuation. By the way, as a method to measure transient characteristics,
The so-called impulse response square integration method of M.R. Schroeder is known. The principle is that when the sound is interrupted from a steady state, the essential transient response characteristic is equivalent to the average of ∞ times of the transient characteristic of the sound receiving point <
S ² (t)> is calculated from the impulse response r(x) between the sound source and the sound receiving point.According to this, the sound pressure level S(t) at a certain point in time t in the transient characteristic is as follows: It is expressed as follows. However, N: noise power, r(x): impulse response, therefore, integral interval [t, +∞]
By squaring and integrating the impulse response r(x), an infinite set average of the squares of the sound pressure level S(t) at time t can be obtained. Actual chamber based on the above principle
There are two main ways to obtain transient characteristics such as reverberation curves. (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. Here, by finding the difference between the square integral of the impulse response r(x) for the integral interval [o, +∞] and the square of the impulse response r(x) for the integral interval [o, t], the transient characteristic < S ² (t)
> is required. FIG. 1 shows the configuration of a conventional device for measuring reverberation characteristics according to this principle. In this figure, the first impulse from an impulse source 2 (for example, a paper pistol) is collected in a measurement chamber 1 by a microphone 3, and the output is sent to a squaring circuit 4 for squaring, and then a switch is activated.
The signal is sent to the integrating circuit 6 via the SW, where the signal is integrated and displayed on the display circuit 7. When generating the second impulse, change the switch SW and connect it to the inverting circuit 5 to invert it, and then display the output via the integrating circuit 6, so that the latter can be subtracted from the former. As a process, a transient characteristic, for example a reverberation curve, is obtained. However, with this double impulse method, it is technically almost impossible to accurately generate two identical pulses as a sound source, that is, to reproduce the second impulse exactly the same as the first. Therefore, there is a drawback that the measurement error increases due to the different shapes of the generated impulses. In addition, the principle of the backward integration method in (2) is as follows: This method is obtained by integrating in the opposite direction, as shown in the following. 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 microphone is recorded on a tape recorder 4', and then the tape recorder 4' is reversed to reproduce the impulse in reverse, and the output is recorded. 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 real-time processing cannot be performed because the collected sound impulses are once recorded on a tape recorder. Therefore, it lacks immediacy. In view of the above, the present invention provides a method and apparatus that can measure transient characteristics, such as reverberation characteristics, with high precision in real time using one impulse, such as a tone burst wave, without repeating reverberation experiment measurements. It is something. That is, the method according to the present invention provides an impulse response r
In the method of displaying or recording the transient characteristics of a transmission system by analyzing (x), a large number of integration intervals [ti (i = 1, 2
...... n), ∞] and square the analyzed impulse response r(x), then continuously calculate the transient characteristics of the transmission system from the integral values integrated in the integration intervals with different integration start points. It is characterized by being displayed/recorded on
Further, the device according to the present invention is a device for displaying or recording transient characteristics of a transmission system by analyzing an impulse response r(x), which is connected to a device for squaring the analyzed impulse response r(x), and a device for squaring the analyzed impulse response r(x). a plurality of comparison devices for comparing the squared output with a specific reference level; a timing control device for receiving the output from the comparison devices and controlling the integration start time to be different in a certain integration interval;
According to such a timing control device

It has a large number of integrating devices that perform [Equation] and a device that continuously displays/records the respective outputs from the integrating devices, and displays/records the transient characteristics of the transmission system in real time. It is characterized by: Examples of the present invention will be described in detail below. FIG. 3 shows the configuration of an embodiment of the invention. This device analyzes the impulse response r(x) and obtains the reverberation characteristics of the transmission system as a series of points, for example.

[Formula] is used to display it on the display device. In FIG. 3, an impulse source 12 and a microphone 13 are installed in a chamber 11, and the output of the microphone 13 is passed through a squaring circuit 14 to a first comparator circuit 16, and further through a smoothing filter 15. and are respectively input to the second comparison circuit 17. The output of the first comparator circuit 16 is input to one input terminal of a flip-flop circuit 28, and the output of the second comparator circuit 17 is input to the other input terminal of the flip-flop circuit 28.
The output of the flip-flop circuit 28 is connected to the AND gate 19i via the timing control device 18.
(i=1, 2...n), and the AND gate 19i (i=
1, 2...n). On the other hand, the output of the square circuit 14 is input to the input terminal of the control gate 20i (i=1, 2...n), and the output of the AND gate 19i (i
= 1, 2...n) outputs are the same control gate 2 respectively.
It is designed to be input to the control signal input terminal of 0i (i=1, 2...n). control gate 20i
The output of (i=1, 2...n) is the integrator circuit 21i
(i=1, 2...n), and the output of the electronic switch device 22 is supplied to the display device 27 via the logarithmic compression circuit 23 and the level axis amplification circuit 24. It's getting old. In addition, a sweep waveform generation circuit 2 is provided in the electronic switch device 22 and the time axis amplifier 26 of the display device 27.
A signal for controlling the sweep is supplied from 5. In this embodiment, after squaring the impulse response r(x) from the sound source, a large number of integral intervals [ti
(i = 1, 2, ...... n), +∞] (however, t ₁ < t ₂
< t ₃ ………), and the amount of energy obtained by integrating this integral interval is displayed continuously on the same screen (or on the same recording paper) in order of the length of the integral interval, and the overall reverberation characteristics are calculated. is displayed. Next, the operation of this device will be explained. Paper pistol and other sound sources 1 in chamber 11
The impulse from 2 is collected by the microphone 13, and the impulse response r(x) is input into the squaring circuit 14 and squared.
The discharge signal is supplied to the second comparator circuit 17, and is also stored in the smoothing filter 15 made of CR. This is applied to the first reference voltage V 1 and the second reference voltage V ₁ of the first and second comparison circuits 16 and 17.
compared with the reference voltage _V2 . At that time, as shown in the figure, the integration is started from the time of the rise of the signal set by the reference voltage _V1 , and the integration is started at the time T at the intersection of the reference voltage _V2 level in the comparator circuit 17 and the pulse curve. end. The reference voltage levels V ₁ and V ₂ can be set to arbitrary levels. In addition,
The end point of the integration interval may be manually set using a timer or the like. Now, in this way, the first and second comparison circuits 1
The output from 6, 17 is a flip-flop circuit 28

[Table] Give the integral of . However, although the upper limit of the integration time is theoretically ∞, in actual measurement, it is the time at which the signal is considered to have attenuated and reached the noise level. These individual integral outputs operate the corresponding electronic switch device 22 having a large number of electronic contacts to create discrete analog information, which is then sent to the display device 27 via the logarithmic compression circuit 23 and level axis amplification circuit 24. Display in . The display device may be, for example, a CRT, a liquid crystal display, a light emitting diode (LED) display, or any other suitable display device. The sweep wave generation circuit 25 may be a commonly used one, and can be used for the electronic switch device 22 and the display device 27.
A signal is provided to control the sweep for the time-domain amplifier 26. Note that in the logarithmic compression circuit 23, the curve <S ²
(t)> is logarithmically compressed and displayed in decibels (dB). The impulse response r(x) processed in this way is determined according to the characteristics of the display device as shown in Fig. 4, and in the case of a CRT, as shown in Fig. 4 a.
In the case of an LED (light emitting diode), it is expressed as shown in Figure b. Furthermore, if an X-Y recorder or the like is used, recording can be performed simultaneously with display. In addition, in the device according to the present invention, the impulse generated from the sound source may be a single pulse with a very short time width or a tone burst signal having a spectrum equal to a noise signal having a certain bandwidth. good. As described above, in this invention, a large number (n) of integration intervals are set for the impulse response r(x), and by shifting the integration start points by a fixed interval, the overall integration can be calculated. From the values, the transient characteristics of the acoustic transmission system, such as reverberation characteristics, can be displayed by appropriate means, and highly accurate measurement in real time is possible. Although discrete, it is possible to obtain reverberation characteristics that appear to be continuous.Moreover, by shortening the shift interval at the start of integration and increasing the integration interval, reverberation characteristics that appear to be approximately continuous can be obtained.

[Brief explanation of drawings]

FIG. 1 shows a system diagram and its waveforms explaining the double pulse method according to the prior art, FIG. 2 shows a system diagram and its waveforms explaining the backward integral method according to the prior art, and FIG. 3 shows the system diagram according to the present invention. An embodiment of the apparatus is shown, and FIG. 4 shows a display example of the embodiment of the apparatus according to the present invention. 11... Chamber, 12... Impulse source, 13... Microphone, 15... Smoothing filter, 16... First comparison circuit, 17...
second comparison circuit, 18...timing control device,
19...And gate, 20...Control gate, 2
1...Integrator circuit, 22...Electronic switch device, 2
3... Logarithmic compression circuit, 24... Level axis amplifier circuit, 25... Sweep waveform generation circuit, 26... Time axis amplifier, 27... Display device, 28... Flip-flop circuit.

Claims (1)

[Claims] 1. In a method for displaying or recording transient characteristics of a transmission system by analyzing an impulse response r(x), a large number of integration intervals [ti(i= 1, 2...n), ∞], square the impulse response r(x), integrate this squared value r ² (x) in the integration interval, and calculate these integral values ∫ ^∞ _t1 r ^2. (x) A method for displaying or recording transient characteristics of a transmission system, characterized in that the transient characteristics of the transmission system are continuously displayed or recorded from dx. 2. A device that analyzes the impulse response r(x) and displays or records the transient characteristics of the transmission system, including a device that squares the impulse response r(x), and a device that is connected to this device so that the squared output reaches a specific reference level. a plurality of comparing devices, which receive the output from the comparing devices, and control each integration start point ti to be sequentially different in a certain integration interval; Therefore, we need a number of integration devices that perform a number of integrations [formulas] at different integration start times in a fixed integration interval, and a device that continuously displays/records the outputs from these integration devices. 1. A device for displaying or recording transient characteristics of a transmission system, characterized in that the device is configured to display or record transient characteristics of a transmission system in real time.