JPS6048693B2 - Reverberation curve measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reverberation curve measuring device, and particularly to a sterilization device that obtains a reverberation curve in real time by processing an input signal to be measured as an analog signal. .

Schr.
The method announced by Mr. Oeder is known.

This method uses a speaker to emit an impulse signal such as a tone burst signal with the required band spectrum,
The reverberation curve (envelope) is obtained based on the signal captured by the microphone of the radiated sound, and according to this method, the collective average of the reverberation curve can be obtained with just one measurement. When the above measurement method is actually applied, conventionally, data analysis has been performed by digitally processing the analog input signal to be measured. For this reason, in the normal case, the input signal must be recorded on a magnetic tape or the like and brought back for digital processing, which requires a lot of time and effort before the measurement results can be obtained. In addition, if you want to know the measurement results immediately at the measurement site, you must either bring the digital processing device to the measurement site, or connect the measurement site and the digital processing device located at a remote location with a data line. In any case, the equipment was large-scale. Furthermore, in digital processing devices, signal processing requires a considerable amount of time because time is spent on signal filtering, integration, and the like. 5 The present invention can eliminate the above-mentioned drawbacks, and provides a storage device in which a reference signal such as a tone burst signal is coded and written, and a storage device in which a reference subcarrier for synchronous detection is coded and written. is provided to perform envelope synchronous detection of the reverberation curve based on the signal obtained by D/A converting the signal read from each storage device, and the frequency of the read clock pulse of each storage device is made variable. It is something.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit system of a reverberation curve measuring device 1 according to the present invention. This reverberation curve measuring device 1 is composed of a tone burst signal input circuit 2 and an input signal processing circuit 3, and a room 4 in which the reverberation curve is measured is equipped with a speaker system.
A foo force 5 and a microphone 6 are placed at predetermined positions.

The tone burst signal input circuit 2 includes an address counter 7, a ROM (ReadOnlyMemOry) 8, a D/
It consists of an A converter 9 and an amplifier 10.

In addition, the input signal processing circuit 3 includes multipliers 11a and 11b).
Low frequency wave detector 12a, 12b) A synchronous detection circuit 15 composed of squarers 13a, 13b and an adder 14, and an amplifier 1
6. Clock generator 17, frequency divider 18, address counter 19, ROMJ2Oa, 2Ob) D/A converter 21a
, 21b) Square rooter 22, divider 23, calibration coefficient unit 24
and an output terminal 25. Then, the tone burst signal outputted from the output terminal of the tone burst signal input circuit 2 is applied to the speaker 5, and the radiated sound is collected by the microphone 6, and a signal (hereinafter this signal is referred to as an input signal) is sent to the input signal processing circuit. The envelope of the reverberation curve obtained based on the detected output is synchronously detected by the synchronous detection circuit 15 through the amplifier 16 from the input terminal of . The output terminal 25 is adapted to be taken out from the output terminal 25.

Next, a circuit operation for obtaining a reverberation curve with the above configuration will be explained. First, tone burst signal E.

The method for obtaining the will be explained with reference to FIGS. 2 and 3. Figure 2 A has a constant amplitude and a single frequency FO
(For example, F.

=50Hz~10KHz) sine wave signal E, =S
in(2πFOt). FIG. 3A shows the frequency spectrum of the sinusoidal signal E. Figure 2 (B shows a modulated signal E whose level changes over a predetermined time d. This modulated signal E2 is, for example, E2=0.54-2πT
O. A signal having a waveform expressed as 46COS(T) can be used.

FIG. 3B shows the modulation signal E. This shows the frequency spectrum of this modulated signal E. The energy of the signal is concentrated near the zero frequency. Next, when the amplitude of the sine wave signal E is modulated by the modulation signal E2,
A tone burst signal having a waveform close to an impulse waveform as shown in FIG. 2C. =el×E2 can be obtained. Figure 3C is a tone burst signal. The signal energy is concentrated around the center frequency, so it is less susceptible to external noise during measurement. The tone burst signal EO obtained as described above is digitally coded and written in the ROM 8 in FIG. 1 in advance. Also ROM2
Oa contains a signal E3=C which becomes a reference subcarrier for synchronous detection.
The waveform of Os(2πFOt) is digitally coded and written in advance, and the ROM2Ob contains the waveform of Os(2πFOt), which becomes the reference subcarrier for synchronous detection. A waveform of =Sin(2πFOt) is digitally coded and written in advance.

In addition, RC (M2Oa, 2Ob omit one of them, and R
A portion of the output of OM2Oa or 20b may be applied to a 90° shift register, and the output of this shift register may be applied to D/A converter 21a or 21b. On the other hand, the clock generator 17 always outputs clock pulses of a constant frequency Fc.

This clock pulse is frequency-divided by a frequency divider 18 into Fc,=Fc to become an input clock pulse p, which is sent to address counters 7 and 19. The address counter 7 is sequentially advanced by the input clock pulse p, thereby causing the digital tone burst signal E to be written into the ROM 8.

is read out. The read signal is converted into an analog tone burst signal E by the D/A converter 9. After being amplified to an appropriate level by the amplifier 10, it is added to the speaker 5 and radiated as sound. The radiated sound is collected by the microphone 6 as a combination of direct sound and reverberant sound reflected from the walls of the room 4, etc. At this time, the next input signal Ei is obtained from the microphone 6.

E, = m(t) ・Sin(2πFOt+φ) In equation 11, m(t) represents the amplitude change of the tone burst signal EO depending on the state of the room 4, that is, the envelope of the desired reverberation curve. be.

Also, the second term φ in Equation 1 means that the tone burst signal EO is in room 7.
This shows the amount of phase change that changes depending on the state of . The input signal Ei obtained as described above is sent to the amplifier 16.
After being amplified to an appropriate level, envelope detection is performed in the synchronous detection circuit 15.

On the other hand, since the address counter 19 is sequentially advanced by the input clock pulse p, the digital signal 3 is read out from -ROM2Oa, and the digital signal 3 is read out from ROM2Oa.
A digital signal E, is read from b.

Note that the address counter 19 can be omitted by also serving as the address counter 7. These beliefs 3, e. are converted into analog signals E3 and e by D/A converters 21a and 21b, respectively, and sent to multipliers 11A and llb.
are applied to one input terminal of each. Multiplier 21a,
The input signal i is applied to the other input terminal of the multiplier 21b, and the signals i and E are inputted to the multiplier 11a. The signals Ei and E are multiplied by the multiplier 11b. is multiplied by Therefore, the multiplication output F, is obtained from the multiplier 11a,
A multiplication output F is output from the multiplier 11b.

As / , Nino is obtained.

Next, these multiplication outputs F, , F2 are sent to the low frequency door wave filter 12a,
12b, and remove the frequency component represented by the first term in parentheses of equations 2 and 3 above, this low-frequency door wave filter 1
The outputs G, , ιG2 of 2a and 12b are obtained.

These outputs G, , G2 are added to the husband squarer 13a, 13b, squared respectively to form G￥, G, and further G〒 and G
By adding H to the adder 14, this addition output X
is obtained.

Next, when the above output X is added to the square rooter 22, the output Y
As, we obtain.

This output Y is added to one input terminal of the divider 23, and the calibration coefficient "2" is applied from the calibration coefficient unit 24 to the other input terminal.
By adding a signal representing , that is, a signal for doubling the output Y of the above equation 7, the output Z of the divider 23 is obtained as Z=m(t)8.

This output Z is the input signal Eicr)m(t
), which indicates the envelope of the reverberation curve.If you want to extract this output Z as an output that changes on a logarithmic scale, you can obtain the desired output by passing the output Z further through a logarithmic amplifier. It's coming.

Next, a case where the frequency to be measured is changed will be explained.
Tetone burst signal written in ROM8, 2Oa, 2Ob.

and signal E. , e, and one wavelength of these signals is made up of a series of digital codes consisting of q discrete quantities.
, 2Ob is F. Hz, the frequency Fel of the input clock pulse p that must be sent to the address counters 7 and 19 in order to sequentially read out the digital code is Fcl==q
・Chitonaru. This is because this input clock pulse p is equal to the oscillation frequency of the clock generator 17 multiplied by the frequency divider 18 (M, n are positive numbers).

Therefore, in the reverberation curve measuring device 1 of FIG. 1, the tone burst signal E is applied to the speaker 5.

, that is, the input signal E from the microphone 6,
frequency F. To change the frequency to be measured by changing the oscillation frequency Fc of the clock generator 17, the frequency division ratio 11 must be changed.
All ROM8, 2Oa, 2Ob by just changing Mn
It is possible to change the frequency of the signal read out. That is, by keeping m of the frequency divider 18 constant and changing n, the measured frequency can be changed logarithmically, and by setting n=1 and changing m, the measured frequency can be changed linearly. can be done. In this case, measurements can be made under the same conditions for each frequency to be measured. It is of course possible to change the frequency Fc of the input clock pulse p by changing the oscillation frequency of the clock generator 17. Next, the envelope signal Z=m of the reverberation curve expressed by equation 8 obtained as described above is
The case where various room acoustic characteristics are determined based on (t) will be explained.

FIG. 4 shows an example of calculating the D value.
The value is relative to the total energy of the input signal Ei. It is generally expressed by the following formula.

The circuit of FIG. 4 consists of a first integrating circuit 31a consisting of a resistor R, a switch S that is closed for a predetermined integration time, an operational amplifier 30aN, a capacitor C, and a reset switch S3; Switch S is closed for the integral time.

, operational amplifier 30b) a second integrating circuit 31b consisting of a capacitor C and a reset switch S, and each output W of the first and second integrating circuits 31a, 31b, .
and a divider 32 for dividing W. By applying the envelope signal Z to the input terminal 33, an output representing the D value is obtained from the output terminal 34. Next, the circuit operation will be explained.

First, before applying envelope signal Z, switch SB, S
4 is temporarily closed and each integrating circuit 31h, 31b is left to discharge.

After that, envelope signal Z is applied, and at the same time, switches S, , S, are closed. This causes the envelope signal Z
are applied to the first and second integrating circuits 31a and 31b, respectively. Then, switch S1 is pressed for a predetermined time, for example, 50
ms, an integral output W is obtained from the operational amplifier 31a.

Also switch S.

When the circuit is closed for a predetermined period of time, for example, one second, the integral output W2 is obtained from the operational amplifier 31b. Next, these integral outputs W,,W. is added to the divider 32 and becomes W, IW
By performing the calculation in step 2, an output representing the D value shown in the [phase] equation can be obtained from the output terminal 34. Fifth
The figure shows an example in which the time center of gravity Ts is determined.

The time center of gravity Ts indicates the center of gravity of the energy of the input signal Ei on the time axis and is expressed by the following equation. The circuit of FIG. 5 consists of a resistor R) a switch S, which is closed for a predetermined integration time, a capacitor C) a first integrating circuit 36a consisting of an operational amplifier 35a and a reset switch S, 3, and a resistor R).
Capacitor C) A second integrating circuit 36b composed of an operational amplifier 35b and a reset switch Sl4, and a resistor R.
.

, switch Sl5, which is closed for a predetermined integration time, and capacitor C. , operational amplifier 35c and reset switch S,
. It has a third integrating circuit 36c configured as follows. Further, the output V of the first and second integrating circuits 36a and 36b,
,V. and a multiplier 38 for multiplying the envelope output Z by the output V3 of the third integrating circuit 36c. Also, the third integrating circuit 3
6c is a voltage E obtained by dividing the power supply voltage E by a variable resistor R.
. is added as an input. By applying the envelope output Z to the input terminal 39, an output representing the time center of gravity Ts is taken out from the output terminal 40. Next, the circuit operation will be explained.

First, switch S, before adding the envelope signal.

,S,. , S, 6 are closed once, and each integrating circuit 36a, 36 is closed.
b, 36c are left to discharge. After that, the envelope signal Z is applied, and at the same time, the switches S,,,S,. close. As a result, the envelope signal Z is transferred to the first integrating circuit 3.
Added to 6a. Then, when the switch S, is closed for, for example, one second, an integral output V, is obtained, and this output V,
is added to the divider 37.

Further, when the voltage EO applied to the third integrating circuit 36c is integrated by closing the switches S and 5 for, for example, 1 second, the integrated output V
.

As, we obtain.

This integral output V3 is applied to a multiplier 38 and multiplied by the envelope output z to obtain a multiplication output V.

×Z is applied to the second integration circuit 36b, and its integration output V. As, we obtain. This integral output V2 represents the magnitude according to the time since the envelope signal Z was applied. Next, this integral output V2 is added to the divider 37 to calculate VJV, and the division output T's is obtained.

This @formula is the time center of gravity T according to the o formula. The time center of gravity Ts can be determined based on this output T'Slr.

FIG. 6 shows an embodiment for determining the reverberation time TR. The reverberation time TR represents the time it takes for the input signal Ei to drop by 60 dB from the peak level. The circuit of FIG. 6 includes a logarithmic amplifier 41, a voltage comparator 42, a resistor R,
resistor R) switch S2l, which is closed for a predetermined integral time;
Capacitor C) Consists of an integration circuit 44 composed of an operational amplifier 43 and a reset switch S2.

Further, one input terminal of the voltage comparator 42 is connected to a logarithmic amplifier 4.
1 output is applied to the other input terminal, and the power supply voltage E,
voltage E divided by variable resistor R2. , is applied as a reference voltage. The integrating circuit 44 is under the power supply voltage. is the variable resistance R. Voltage E divided by . . It is designed to integrate and divide. Further, when the output of the voltage comparator 42 reaches a predetermined level, the switch S2 is opened to stop the integration of the integrating circuit 44. By applying the envelope signal Z to the input terminal 45, a signal representing the reverberation time TR is taken out from the output terminal 46. Next, the circuit operation will be explained.

Switch S first.

. is temporarily closed and the integrating circuit 44 is left to discharge. After that, the envelope signal Z is applied to the human power terminal 45, and the switch S is turned on at the same time. , close. As a result, a signal Z' shown in FIG. 7 in which the level of the envelope signal Z changes logarithmically is obtained from the logarithmic amplifier 41, and this signal Z' is output from the voltage comparator 4
Added to 2. Reference voltage θEO of this voltage comparator 42
, are selected to be equal to the level when the peak level of Z' drops by, for example, 15 dB. Therefore, in FIG. 7, when the signal Z' reaches its peak level at time tl and then attenuates by 15 dB, an output is obtained from the voltage comparator 42, and based on this output, the switch 5S. , will be opened. At this time, the integral output T'R of the integrating circuit 44 is obtained.

1 By multiplying this output value R by 4, the reverberation time TR when the level of the signal Z' is attenuated from time T to 6 dB (4×15 dB) can be found.

Various room acoustic characteristics such as the above-mentioned D value, time center of gravity T, and reverberation time TR can be obtained by a method different from the method described in FIGS. 4, 5, and 6. For example, the first
The envelope signal Z obtained by the reverberation curve measurement device 1 shown in the figure is A/D converted directly or after passing through a logarithmic amplifier, and the converted digital signal is processed by a digital processing device to obtain the above-mentioned various room acoustics. Characteristics can be determined.

In this case, compared to the conventional method of digitally processing the input signal Ei from the beginning, the processing time is shorter and the amount of data to be processed is also smaller, so it can be processed sufficiently by a small J-type digital processing device. I can do it. The present invention provides a reference signal E having a predetermined band spectrum.

a first storage device 8 that stores a code signal obtained by converting a signal waveform into a digital code; and a D/A that converts the code signal read from the first storage device 8 into an analog signal.
A converter 9, an output terminal that supplies the output of the D/A converter 9 as a reference signal to the systems under test 4, 5, 6, and the reference signal is obtained by passing it to the systems under test 4, 5, 6. An input terminal to which an input signal to be measured is supplied, and a reference subcarrier E for synchronous detection. , e, and converts the code signals read from the second storage devices 20a, 20b into analog signals. D/A converter 21a to convert,
21b, an analog synchronous detection circuit 15 that synchronously detects the input signal under test using the outputs of the D/A converters 21a and 21b as reference subcarriers, and a square root circuit that takes the square root of the detected output of the analog synchronous detection circuit 15. 2-2, and addressing devices 7 and 19 that generate read addresses for the first and second storage devices 8, 20a and 20b,
It has a clock pulse generation circuit 17 that generates a common clock pulse for changing the respective read addresses synchronously, and a variable means 18 for changing the frequency of this clock pulse. The present invention relates to a reverberation curve measuring device characterized in that it obtains an output signal proportional to the reverberation curves of the systems to be measured 4, 5, and 6. Therefore, according to the present invention, the following effects can be obtained.

(1) Since the input signal to be measured is processed as an analog signal, signal processing can be performed in real time, and measurement results can be known immediately. (2) The frequency to be measured can be easily and arbitrarily changed by simply changing the frequency of the clock pulse for reading, and each frequency to be measured can be measured under the same conditions. (3)
The device can be made smaller and lighter.

(4) Since the amount of data to be processed is small, even in the case of digital processing, signal processing can be performed sufficiently by simply connecting a small digital arithmetic processing device.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2A,
B and C are waveform diagrams showing the formation process of tone burst signals;
Figures 3A, B, and C are diagrams showing the frequency spectra of each waveform in Figure 2A, B, and C, Figure 4 is a circuit diagram showing an example for obtaining the D value, and Figure 5 is a time diagram. FIG. 6 is a circuit diagram showing an embodiment for obtaining the center of gravity Ts, FIG. 6 is a circuit diagram showing an embodiment for obtaining the reverberation time TR, and FIG. 7 is a waveform diagram of an envelope signal used to explain FIG. 6. be.

Claims (1)

[Claims] 1. A first circuit that stores a code signal obtained by digitally encoding the signal waveform of a reference signal having a predetermined band spectrum.
a storage device, a D/A converter that converts the code signal read from the first storage device into an analog signal, and an output that supplies the output of the D/A converter to the system under test as a reference signal. a terminal, an input terminal to which an input signal under test obtained by passing the reference signal to the system under test is supplied, and a second code signal storing a digital coded signal waveform of a reference subcarrier for synchronous detection. A storage device, a D/A converter that converts the code signal read from the second storage device into an analog signal, and a D/A converter that synchronizes the input signal under test using the output of the D/A converter as a reference subcarrier. An analog synchronous detection circuit that performs detection, a square root circuit that takes the square root of the detected output of the analog synchronous detection circuit, an addressing device that generates each read address of the first and second storage devices, and synchronizes the read address. a clock pulse generation circuit that generates a common clock pulse for changing the frequency of the clock pulse, and a variable means for changing the frequency of this clock pulse, and output from the square root circuit that is proportional to the reverberation curve of the system under test A reverberation curve measuring device characterized by obtaining a signal.