JPS63252263A - Signal measurement - Google Patents

Abstract

PURPOSE:To achieve a measurement of power of a signal intermittently transmitted from a transmitting section effectively without being accompanied by noise, by receiving the intermittently transmitted signal to accumulate differences of integrated values between first and second sections of a squared of a waveform thereof. CONSTITUTION:A pulse (a) with a cycle 2T generated by a pulse generator 1 is passed through a band pass filter 2 and outputted from a speaker 3 as acoustic signal. On the other hand, in a receiving sector, the pulse is converted into an electrical signal with a microphone 4 and a proper amplitude is applied to an attenuator 6 through a band pass filter 5 to determine the square of a waveform with a square device 7. Then, the squared value is applied to a differential accumulator 8 to accumulate differences of integrated values between first and second sections. When the last pulse is generated from the pulse generator 1 and the final differential accumulation ends, the results are displayed at an output section 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal measurement method, and particularly to a method for effectively suppressing noise in signal power measurement.

A well-known noise suppression method is a synchronous addition method in which received waveforms are added in synchronization with signals. In this method, the power of the noise component can be reduced to 1/N of the signal on average by adding the signal N times. Therefore, SNN
To improve by 1329 dB, it is enough to perform signal addition 100 times, but for example, when measuring the sound insulation of a wall using pulsed sound, the number of additions increases in order to improve the S/N ratio in high frequency bands, and it takes time to measure. The problem arises that it takes a long time and that high precision is required for synchronization.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a signal measurement method that effectively reduces noise in signal power measurement and does not require high accuracy in electrical manufacturing.

Now, let the k-th reception response w rl, (t), its signal component be s, (tl, and the noise component n k (t), then r,
ft) = s k(tl + nl, m
It can be expressed as (1). It is assumed that the signal component is sufficiently attenuated after time T has elapsed, and that the noise component is present throughout the entire time.

Here, the value obtained by squaring equation (1) and integrating over Ti from time t=0 is set as Rk(0), and 5k(o) and Nk(O) are the square integral value of the signal component and the square of the noise component, respectively. integral value,
If Ek(0) represents the integral value of the product of the signal component and the noise component, then TLkfol=Skfo)+2B, k(o)+Nkfo
) (2).

Similarly, by squaring equation (I), t=T to 2T-! Rk(r) is the integrated value, and Sk■ and NkCr) are the integrals of the squared values of the signal component and noise component, respectively: L.If Rkm is the integral value of the product of the signal component and the noise component, then Rkm" 8@
(T)+ 2 El (T)+ N+, (n f
3).

According to the signal measurement method according to the invention, the first interval (t=0
~T) and the integral value of the square waveform of the reception response in the second interval (t = T ~ 2T) = P is the accumulated value from 1 to K, and S, Ω) = S, K(O ), then S, ■<s, a
), E, (1), 9E, D), so if these minute terms are ignored, it becomes approximately P/K = S, (0) + E + M, -M2 (41. However, E is ( 2) The cumulative value of the second term (takes positive and negative values) on the right side of the equation is divided by K, and Ml and M2 are the third term on the right side of equation (2) and (3), respectively. It represents the cumulative value of noise power divided by K.

Since Ekρ) is an integral case of the product of a mutually uncorrelated signal and noise, as K becomes larger, E becomes a sufficiently small value to be ignored in equation (4). Furthermore, Ml and M2 are the average values of the noise power in each section, and as K becomes larger, they approach one value according to the "law of large numbers" and the difference between them becomes sufficiently small. Therefore, if K becomes large, P/ can be expressed as =SI(01(5)) with sufficient approximation.

Although it is difficult to demonstrate the noise suppression effect of the signal measurement method according to the present invention in general, it is possible to consider the following cases to see how large the effect is. That is, as a special case, if noise is added only to the first or second section of one measurement in K measurements, the noise suppression in such a case will be 1/. If there is noise in both the first and second sections (normal case), the noise suppression effect is much greater than in the above case. Therefore, it can be said that this measurement method can provide an extremely superior noise suppression method compared to the synchronous addition method.

Furthermore, in this signal measurement method, the signal component only needs to fall into the first (or either) interval in the accumulation of response signals, so the accuracy of synchronization is lower than that of the conventional synchronous addition method. It could be much lower. Therefore, it is possible to provide an economical device when put into practical use.

Next, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram of a signal measuring device according to an embodiment of the present invention. Pulses generated at a period of 2T are passed through a desired bandpass filter and output as an acoustic signal from a speaker. On the other hand, on the receiving side, the signal is converted into an electrical signal by a microphone, passed through a bandpass filter, and an appropriate amplitude is given by a 7-tensioner to obtain the square of the waveform. Accumulate the difference between the integral values of . When the last pulse is emitted from the pulse generator and the last difference accumulation is completed, the result is displayed at the output. For example, if there is a wall between the speaker and the microphone in Figure 1, and the degree of sound insulation is being measured, the sound pressure at the speaker side is given by the square integral value obtained from one pulse generation, and the wall If the cumulative value is divided by 20 to obtain the power value, then the sound insulation degree is the decibel value obtained by dividing the square integral value on the speaker side by the power value and expressed in logarithm. It will be given by

All or part of the calculation-related portion of the device shown in FIG. 1 may be performed by digital signal processing. For example 7
The output of the tutenator may be converted into a digital signal by an AD converter, and the following signal processing may be performed by digital calculation.

Also, although there is no particular benefit from the increase in calculation processing, if the length of the first section and the length of the second section are different, then if those lengths are T and T2, then the first section will be The integral value of the interval can be multiplied by T2, the integral value of the second interval can be multiplied by 11, and then the difference between these integral values can be calculated, thereby obtaining a value that accumulates the difference over the measurement interval. .

Note that the present invention is not limited to the above embodiments.
For example, the integral values of the first section and the second section may be summed over the signal measurement section, and the difference between them may be determined to obtain a value that is an accumulation of the differences.

4. Brief Explanation of the Figures Figure 1 shows a block diagram of a signal measurement device (acoustic measurement) based on the present invention and waveform examples of each part thereof.

Claims (1)

[Claims] 1. Determining a squared waveform or a rectified waveform from the received waveform of each signal in a receiving section configured to perform signal measurement in synchronization with each signal intermittently emitted from the transmitting section; determining a value by accumulating the difference between an integral value in a first interval and an integral value in a second interval of the squared waveform or rectified waveform over the interval of the signal measurement, and outputting a quantity corresponding to the accumulated value; A signal measurement method comprising at least: 2. The signal measuring method according to claim 1, wherein the integral value is obtained by adding sampled values of the square waveform or rectified waveform. 3. Claims 1 and 2, wherein the difference is obtained by subtracting the sampled value in the second interval from the sum of the sampled values in the first interval. Signal measurement method described. 4. The signal measuring method according to claims 1, 2, and 3, wherein the second interval is set at a time when each of the signals disappears or sufficiently attenuates. 5. The signal measuring method according to claims 1 to 4, wherein the length of the first section and the length of the second section are equal. 6. The signal measurement method according to any one of claims 1 to 5, wherein the signal measurement is related to sound insulation measurement.