JPS6020127A - Indoor reverberation time measuring method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a method for measuring indoor reverberation time.

[Technical aspects of the invention] Reverberation time is one of the important factors in evaluating the acoustic effects in a room (spreading feeling, sound clarity, sense of presence, etc.). Physically, the time it takes from the moment the sound source is stopped until the sound pressure at the measurement point in the room reaches 160 dB is reverberation 11;
It is defined as 7 hours.

Traditional methods for measuring indoor reverberation time include white noise,
After the sound such as a high-speed level recorder is transmitted into the room, it is stopped, and after this stop point, the electrical signal taken out from the microphone installed in the room is logarithmically converted, and then the reverberation sound is recorded on the recording paper of the high-speed level recorder. The reverberation time in the room was determined from the slope of the recorded attenuation waveform. However, with this method, there is a problem with the reliability of the results, and it also requires a huge amount of labor and effort for humans to read the slope from the attenuation waveform on the recording paper. ``I had to spend 51 hours getting used to it.

For this reason, recently, a test sound field is created in the city to create a diffused sound field in the room, and then the sound field is stopped, and from the point when the sound field is stopped, the electric radiation from the microphone that receives the reverberant sound is emitted. The rimbling data obtained in this way is converted into a digital signal by a △/D conversion circuit at a fixed zumbling time interval, and the rimbling data obtained in this way is
5, apply a straight line approximation to the least squares method, and measure the reverberant intercostal space by reducing the slope of A, thus simplifying the measurement.
There are many cases where the measurement time is reduced to zero.

1 Background technology problem Fish 1 More J, Eel reverberation? 5. The electric signal from the IC microphone was received, and the electric signal from the IC microphone was rimbling and converted into digital and Q signals. L from 21 bon?Q
Inside, the measurement target and the reflection high component that should be Ij,
The signal contains the direct 1) 1 go, 01) futomi component, and the 4 I' component is included.The L signal is directly limbled and the C1!1 limbling data is processed. Therefore, there was a large error in the calculation result of (a). In other words, FIG. 1 is a diagram showing an average curve of the envelope of a signal from a microphone that receives sound emitted from a sound source in the room. The first half of the attenuated waveform after the time (stopping 1-) is affected by the direct sound from the sound source. The calculated slope 8 shows a value different from the slope B which is obtained by subtracting 0 from the reverberant sound (anti-q4 sound component) to be measured. In addition, the latter half of the attenuation waveform in Figure 1 is affected by background noise.
The slope C is different from the slope B, and affects the slope B. Therefore, the signal from the microphone I's phone is lean-bred as it is, and the lean-bring data that is
Calculation 1: There was a large error in the reverberation 11) measurement results obtained by calculating the reverberation with a torch.

[Object of the Invention] The present invention limps the signal from the microphone [I 11, 4 () for a certain period of time, and as a result,
[7] In order to solve the problem of 1-1-j; in the method of measuring the room temperature from the obtained rimbling data, The purpose of the present invention is to provide a method for measuring indoor reverberation 11 and Y that can measure the reverberation 111 and 111 between L and C reverberations to extremely iE rKF based only on rimbling data that is not affected by dark G sounds. The purpose is

[Summary of the Invention] Fig. 2 is a diagram C showing an average curve of the envelope of a signal from a microphone that receives 71 radiated from a sound source in a city by a microphone indoors.

In FIG. 2, the time 1: dO from the sound source point A until the direct sound from the sound source to the microphone is no longer received is expressed by equation (1).

1: do=d/c...<1) Where d: Distance from the sound source to the microphone C: Speed of sound in the medium (for example, air) in the room. The signal from the source contains reverberant sound (counterpart sound component) and direct sound, and does not indicate accurate attenuation of reverberant sound. Therefore, it is necessary to limp the signal from such a microphone at regular time intervals and delete the data in tdO that is d3 in the limp data obtained by adding J+7.

I will elaborate on the deletion of limbing data in C10. On the other hand, I input the shape of the city into the computer in advance for IT R, which has a 4-cost, 1-y property. For example, in the case of a rectangular room, input the width x, depth Y, and height Z. Distance from the sound source to the microphone! ! i11 d maximum 1i
dmax is expressed by equation 2) due to its relationship with the chamber shape.

d max =2·-(2) Therefore, once the room shape is determined, Diit, d from the time of sound source A until it is no longer affected by direct sound.

The maximum 1 [J t d max is the maximum of 1 [J t d max,
It can be determined by equation (3).

t dmax = dmax /c -------・(3);
It g? At 4m, there is actually reverberation I from sound source A.
[, 1 Let id+ be the time required to start importing data to save time, then the condition of equation (7I) l dl ≧
L: d max −−−−−−(4) If we make it ＼b, after td+, JIM enters 5L in total, and the ringing j′−in the evening, the influence of O′l articulation is reduced. Not milled. To specifically determine tdl, suppose that the Δ/D conversion circuit is subjected to rimbling of the signal from microphone 1-1 for every integer At, then tdmaX is (5
) satisfies the condition A'1 of the equation tc 1'.

rn −1t < t: +:jmax ≦ <m−1
−1) dt−−−−−−(5)<m=1.2, −m
) Therefore, from the condition of equation (4), td+ = (ITI-1-
1)・A1 is stopped.

ζ△/Leanbling time interval by D conversion circuit/
I(, is represented as a floating point number (J'< 1)
, l: to tdl.

This eliminates the need to import into the computer unnecessary rimbling data that is affected by the C1 accompaniment.

Next is a dark acquaintance? The method for deleting limp ring data affected by item 3 will be described below. In Figure 2, there is darkness in the room before the sound source is J. Average IUL of J sound (level)
(measured by the signal from the microphone), but in reality, background noise has a large variability. Therefore, since there is a small probability that l u is equal to the background noise α (level) after the point at which the sound from the sound source stops forming, the average value Lu of the background noise from the signal from the microphone , the standard deviation σ is determined in advance using a bullet measuring machine. Considering the variability of background noise, LLJ + σ is the standard background noise level, and the value (lu + σ
) -1, -K by writing the lowest limit value of the sound pressure level in 1 non-pulling data to be imported into -
C. Reverberation time can be measured without being affected by background noise (K can be given as 6 to 10 dB from the accuracy of noise words, etc.). In FIG. 2, td2 indicates the time (period) during which sampling data is taken in at i+times.

The present invention has been made based on the above findings, and includes emitting test sound into the room from a white source installed in the room to make the room a diffused sound field, and stopping the emission of the test sound. Based on the limp ring data obtained by sampling the signal from one microphone installed in the room at a constant interval of 1.1, the reverberation in the room C1 is
The reverberation in the room playing between 5 and 10 seconds ■1 measurement method is L12, and the distance Ii between the source and the microphone 11! Il
and the speed of sound in the indoor medium.1) [i
1L (L1 of i contact
The period of 1R5 for which the ring no longer receives the chi sound has passed from the stop 1 point, and this point is the start of the lean ring + 1r.
71:,9, the average of Ili:i dissolution in the room 1n
'iOJ, and (τ()II - Based on the deviation, the room receives the shadow of the dark battle 1-1 IJ', and the pressure level is set to 71 to the microphone [] It is characterized in that the measured sound pressure level reaches J111Sjj from 1.jQ to the end point of the ring link.

FIG. 3 is a diagram showing one embodiment of the indoor reverberation time measurement bag for carrying out the present invention.As shown in the figure, is the measuring room, 2 is the speaker installed in room 1, 3 is the microphone installed in room 1,
4 is a noise generator (white noise optical generator), 5 is a bandpass filter that passes (transmits) a signal in a frequency band selected from the output signal from the noise generator 4, and 6 is a bandpass filter from the bandpass filter 5. This is an amplifier that amplifies the signal and drives the speaker 2. A bandpass filter 5 filters a plurality of frequency bands to an external control signal.
tlli! Zuru.

Reference numeral 7 designates a band-pass filter having the same structure as band-pass filters 5 and 1, which selects the output signal from the microphone 3 and passes (transmits) it to a receiving station in the frequency band 7j.

The signal from the bandpass filter 7 has an effective value (RMS
) is input to circuit 8, where its effective value is detected, then input from this effective value circuit 8 to logarithmic conversion circuit 9, where it is converted into a number, and then converted into △/D (analog/digital). The signal is input to the circuit 10 and converted into a digital signal at a predetermined sampling time interval, and then from this A/D conversion circuit 10 to the interface 11.
It is input to 1tlHj3112 via.

Bandpass filter 5.7I, 1, interface'
11 to select the frequency band. The A/D conversion circuit 10 will be in November (Non-bring 114, 1-kun, fli
C is controlled by tX5t12.

As mentioned above (by the 14th generation, the following J:
The reverberation time within the sky 1 is measured. Cb is applied to the frequency band of the band pass filter 5.7 by pre-selecting a predetermined frequency band and applying the selected 1
Regarding this frequency band, the noise inside the room 1 is measured. Meanwhile, the speaker 2 is driven by a voltage V, and the signal from the microphone 3 is passed through a bandpass filter 5, an effective value circuit 8, a logarithmic conversion circuit 9, and an A/D conversion circuit 10 at predetermined rimbling time intervals. Perform Δ/D conversion. From this digital signal, the average of the background noise is 1.
Ift l u and standard t%fg difference σ are calculated by il[112. Then, at the stop machine 12, the measurement is completed.■
, the sound pressure level at one point is determined (Lu + σ → -1) (K is the correction value as in the book).

Next, at the 4th stop, the control signal from 12 changes the speaker 2 as the sound source to A, and from the sound pressure level measured by the microphone 3, ((-U + σ0K) d B , l;
Adjust the output of amplifier 6 in advance to increase the number of 10 dB (d3<), and add 81 to 4 and 12
When the timer in the computer 12 starts operating and the time accumulated by this timer reaches a predetermined time that is sufficient for the room 1 to become a diffused sound field from the speaker 271, the computer 12 starts operating. Speaker 2 is turned off by the 011 code from .

At this point of OFF, the timers in Calculation 1 and 12 are reset and immediately start running again.

Then, when the cumulative time of the timer reaches tdl, A
The ring ring data from the /D conversion circuit 10 is sent to the computer 1.
Start importing in 2.

Then, a3 in the computer 12 compares the sound pressure level in the sampled data taken into this with the above-mentioned (Lu + σ + K), and imports the leanbring data into the computer 12 until the two match. , and when the two match, the import of the limbing data into the ff1RBJ 112 ends.

Then, in this way, it is imported into il edition '+ 2 and becomes lc data! Yuzui-C Crying Machine 12 Smell-C,
The reverberation time within the room 1 is measured.

[Effect of the invention 1] As explained above, the present invention can obtain resampling data that is not affected by J, repo, direct sound, and in noise, and based on this, the reverberation time in the room can be determined by Can be measured accurately.

[Brief explanation of drawings]

Figures 1 and 2 show all the sounds in the room produced by the microphone.
FIG. 3 is a configuration diagram showing an embodiment of an indoor reverberation time measuring device for carrying out the present invention. . 1...Room 2...Speaker 33...Microphone 11...Noise generator 5.7...Pandobassorter (U...Amplifier 8...°East j
(a circuit 9)...logarithmic conversion circuit 10...Δ/1)
Conversion circuit 12...Kunshiniso Application agent Patent attorney Gobe Kikuchi

Claims (1)

[Claims] A test sound is emitted into the room from a sound source installed in the room.
to diffuse and raise the room, and make the test sound 11.
ζ1 and lean-pulling the signal from the microphone installed in the room at regular time intervals, thus 111
In the indoor reverberation time measuring method for calculating the reverberation time in the room based on the zumbling data obtained, the distance between the sound source and the microphone and the indoor medium 7
The time point at which the time elapses from the time point N,j of stopping emission of the test sound until it is no longer directly affected by the sound, determined based on the speed of sound of 1, is the time point at which the sampling starts, and Measurement based on the sound pressure level unaffected by the 11 combined noise in the room, based on the average value i1'i and standard deviation of the background noise in the room, from the microphone. A method for measuring reverberation time in a room, characterized in that the time point at which the sound pressure level reaches the end point is the time point at which the first non-ringing period ends.