JPS61245698A - Acoustic characteristic measuring instrument - Google Patents

Abstract

PURPOSE:To execute a correct sound field evaluation which has coincided with an aural sense, by measuring an acoustic characteristic, based on output of a microphone which has been installed to an actual human body or a dummy ear part. CONSTITUTION:A dummy mannequin 12 is placed at a listening point for listening to a reproducing sound from loudspeakers 11L, 11R which have been placed as a pair of right and left sound sources in a room A, and microphones 13L, 13R are installed to both ear holes. From signal generators 14L, 14R, a random noise such as a pink noise, a white noise, etc., having no correlation to each other is generated, and becomes a source signal of the loudspeakers 11L, 11R through transmission characteristic correcting devices 15L, 15R of a graphic equalizer, etc., and amplifiers 16L, 16R. An output of the microphones 13L, 13R becomes a power addition value of an acoustic signal from the loudspeakers 11L, 11R, and by deriving an addition or a power addition average by an arithmetic unit 17, a sound field can be handled as one transfer function, and a result of the operation is displayed on a display device 18.

Description

Detailed Description of the Invention Technical Field The present invention relates to an acoustic characteristic measuring device, and in particular to an acoustic characteristic measuring device that measures the distance between a plurality of sound sources provided corresponding to a plurality of channel signals and a listening point for listening to the reproduced sounds from these sound sources. The present invention relates to a measuring device for measuring acoustic characteristics.

BACKGROUND ART Conventionally, there has been a device of this type as shown in FIG. In the figure, in a predetermined room A, there are a pair of left and right speakers 1,
L, IR are provided, and these speakers IL
, 'tR, the signal output from the signal generator 2 is supplied via a transmission characteristic correction device 4L such as a graphic equalizer and an amplifier 5L or a correction device 4R and an amplifier 5R by switching with a changeover switch 3.

The signal generator 2 outputs signals such as rubber, pink noise, impulse, white noise, warble tone, and sine wave.

In order to measure the transfer function in the sound field established by the reproduced sounds from the speakers], L, and IR, or to correct the sound field characteristics by electrical means based on the measurement results, a point in the sound field ( For example, speaker IL
An omnidirectional microphone 6 is installed at the listening point where the sound from the IR is heard. This microphone 6
By displaying the output on the display device 7, the sound pressure frequency characteristics are measured.

Here, as a method to actually measure the acoustic characteristics, since there are two or more speakers in a stereo sound reproduction system with two or more channels, the in-phase signal is sent to these two or more signal sources. Generally, there is a method of applying and measuring, and a method of measuring and evaluating each independently. In the former method, signals from each speaker are vector-added at a microphone point, and the result is output as the sound pressure received by the microphone. In the latter method, □ is output as the sound pressure received by the microphone from two independent speakers.

In the conventional device configured as described above, so-called one-point measurement is performed using one microphone in a sound field where no humans are present, but in an actual sound field, humans are
If the human body enters the sound field, the sound field will be disturbed, and since real images have directional characteristics unique to humans, it has been difficult to make measurements consistent with the auditory sense. Unfortunately, stereo playback devices with two or more channels have the disadvantage that it is difficult to measure overall external characteristics. Furthermore, in cases where the listening point is asymmetric, such as in a car-mounted audio system, the two transfer functions from each speaker to the sound receiving point are replaced with one, and when comprehensively evaluated, the material becomes significantly smaller. There were drawbacks such as difficulties.

SUMMARY OF THE INVENTION The present invention has been made to eliminate the drawbacks of the conventional devices as described above, and an object of the present invention is to provide an acoustic characteristic measuring device that can perform accurate sound field evaluation consistent with auditory sensation.

The acoustic characteristic measuring device according to the present invention includes, in a stereo sound reproduction system including a plurality of sound sources provided corresponding to a plurality of channel signals, a real human body located at a listening point that listens to reproduced sounds from the plurality of sound sources; The apparatus is characterized in that it includes a measurement system having a microphone attached to the ear of a tummy mannequin or dummy head, and measures acoustic characteristics based on the output of the microphone.

Example Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, there are a pair of left and right speakers in a predetermined room A],
L L and 11 R are arranged as sound sources, and a sound field is formed by reproduced sounds emitted from these speakers.

Speaker 11. A dummy mannequin (only the head part is shown) 12 is placed at the listening point where the reproduced sound from the Fts is heard, and microphones i3L and 13R are attached to both ear holes of this dummy mannequin 150. The dummy mannequin 12 has a real human body structure, including a torso, legs, etc., and is set so that the sound absorbing power of its surface is approximately equal to the average sound absorbing power of a human wearing clothes. FIG. 2 shows the sound absorption power of a real adult human body when wearing clothing, which was determined using a method based on the reverberation method. Sound absorption power changes depending on the type of clothing, and the arrow range shows the range of variation.

Note that the dummy mannequin 12 may be dressed in clothing similar to that of a real human body, so that it has almost the same sound absorption power as a real human body when wearing clothing. Also,
Instead of the dummy mannequin 12, a real human body or a dummy head may be positioned at the listening point, and the microphones 13L and 13R may be attached to the auricles or ear canals of both ears.

A signal generator 14 T, , ], '4 for independently driving the pair of speakers 11 L and 11 R.
B is provided, and these signal generators 14L, 1'4
Random noise (or pseudo-random noise) such as pink noise and white noise, which are uncorrelated with each other, is generated from each R. Each of these uncorrelated source signals is
Transmission characteristic correction device such as graphic equalizer 1.5
L', 15R, and amplifier 16L.

Speaker 1 ], L, 1.1 R via 16R
becomes the source signal.

Since the source signals of speakers IIL and IIR are uncorrelated, in the sound field, speakers 11L and IIR
The power summation of each of the acoustic signals output from the . Therefore, the microphones 13L, 13
The output of R is also output from the speaker 11 L at that position,
This is the power addition value of the acoustic signal from 11R. By further adding or averaging the outputs of the microphones 13L and 13R in the arithmetic unit 17, the sound field can be treated as one transfer function. The calculation results of the calculation device 17 are displayed on the display device 18.

Next, the operation of the present invention will be explained.

First, using geometric acoustic expression, we will compare the sound reception characteristics of a real photograph with those of an omnidirectional microphone.

The sound reception characteristics of a live photograph are shown as impulse responses B and D on the eardrum surface.
The impulse PrL(t) for one ear is expressed as θ〆n (n is the number of sound sources, θ is horizontal,
(perpendicular angle), the formula FtD-ΣPj(t)・DM(θre)・G can be obtained as the sum from all directions in the 4π space surrounding this (t is the number of the sound source. , for example, becomes the t-th sound source). Here, DM eft(e for flS
ft is the actual external transfer function, and G is the internal transfer function corresponding to the acoustic impedance in the ear.

For example, in a vehicle interior, the sound source, wall surface, seat, and listening point are located close to each other, so that a part of the free path of the sound wave changes depending on the seating position of the listener.

This change is defined as the acoustic disturbance degree Dn (θ〆2).

Still, if we define the ear's directional characteristics as the head-related transfer function DR (θ〆phrase), then we can write DM(θy' i ) −'Da (θ$i)・Dn(
θri, ), and the impulse response including this is ap
-ΣPL(t)・DR(θgua)・DD(eft)・G
...It is expressed as (1).

On the other hand, if we consider the case of an omnidirectional microphone, the degree of acoustic disturbance is so small that it can be ignored, so in the same way, if we take the impulse response generated in the vibration system as RM, ~=ΣPi(t)
(2) appears.

The difference between equations (1) and (2) above represents the difference in characteristics in these sound receiving systems.Among the parameters of equation (1), the internal transfer function G is independent of the direction of sound incidence. Since it is almost constant, the inverse transfer function can be normalized in a one-dimensional electrical system. However, since the directional characteristics DB and the acoustic disturbance degree DD are based on three-dimensional spatial sound receiving characteristics, they are simply
It cannot be replaced by one-dimensional processing in an electrical system. That is, it is difficult to convert the data of the difference in characteristics between these two sound receiving systems.

As is clear from the above, the microphone, which is the basis of the measurement system for sound field measurement, needs to have a directivity characteristic (head-related transfer function) and acoustic disturbance degree equivalent to those of a real human body as sound receiving characteristics. . Therefore, it is effective to use the microphones 13L and 13R attached to the ears of the dummy mannequin 12 having a real human body structure, as in this embodiment.

In the sound receiving system described above, the left and right ears have a certain correlation with each other in a general sound field (excluding the case of headphone sound reception). For this reason, it is difficult to control the transmission characteristics, which serve as an index for sound field correction, independently for the left and right ears. Therefore, if the characteristics obtained by adding the transmission characteristics of the left and right ears are the transmission characteristics 7 of the sound receiving system 1, then 0 size F? (7
), -v The power summation average of the outputs of the microphones 13L and 13R is determined by the arithmetic unit 17, and the resulting characteristics are used for sound field evaluation.

In order to capture the signals generated in both ears as mutually independent average levels, the arithmetic unit 17 calculates the vector (
The power spectrum (absolute value of sound pressure at each frequency) is obtained by eliminating components (including phase), and these are added between both ears. Further, each of the added transmission characteristics is converted to an average level of the 1/3 oct band, and this is evaluated as the transmission characteristic. This is because the 173 oct band roughly corresponds to the human critical bandwidth, so analysis data using this band matches the auditory impression well, and changes in the narrow band spectrum within this band have little effect on the auditory impression. be.

By the way, when measuring by driving the speakers of each channel simultaneously, an uncorrelated signal between each channel, such as random noise, is used as the source signal for the speakers IIL and IIR, but this is not possible under the measurement conditions described above (each This is because, in order to satisfy the requirement (power addition between channels), it is necessary that the measurement signals on the sound source side have occurrence probabilities that are uncorrelated between each channel. For this,
It is possible to prevent the signals of each channel from interfering with each other near the listening point, and it is possible to reduce the positional distribution of transmission characteristics during measurement.

In the process of performing the above-mentioned power addition process, the multiple (two-channel stereo) sound sources and the two sound receiving systems (binaural) each have independent transfer functions, and the sum of all these transfer functions is It becomes one transfer function between the sound receiving system and the sound source. In order to treat each of these transfer functions independently,
It is necessary that the signals from the sound source be uncorrelated between each channel. This is explained as follows.

In FIG. 1, there are two sound sources (speaker 11L).

11R) is SL, the output of the 5R12 sound receiving systems (microphones 13L and 13J is ML, M, and the transfer function from the sound source to each sound receiving system is GLL * (3LR + GRL).
+GRR, the outputs ML and MR of each microphone in the sound receiving system are expressed as follows. When determining the transmission characteristic as M "" MR + ML, this power addition value is M2, so
M”-(S R-GRR) ”+ (S L-GL
R)2+ (SL 4LI,)2+ (SR-Gru,)
2 + 2 (j■possible 500 [Yaku 7.
G plate)2・(SR・GRJ,)2+ (81,・Gr,
R)2・(SL-GLL)2-1-(SL-GLR,)
2+-(SR/GRL) -2('5R2(G plate/GR
I, ) + 5L2 (GLR - GLL) ) The product of the function values converges to 0) ,', M2 = 5R2 (GRR + GRL)'' + 5L2
(Gr, L+GLR)”= (SR(GRR×GRL)
+5L (GLL 10L autopsy) -8R8L (G plate + GRL>
・(GLI, 10 GLR) = lsR-a plate + 5a-(3B
L+ SL・Jungr, +SL・GLRl'-' (GRR
It can be calculated as 10GRL) ・(Gu, 10LR) = 0.

In addition, in the above embodiment, when driving and measuring multiple sound sources at the same time, the source signals are uncorrelated between each channel.
However, if temporal processing is used to drive each sound source, the source signals do not necessarily have to be uncorrelated; in short, the signals emitted from the sound sources do not necessarily have to be uncorrelated between each channel. That's fine.

FIG. 3 is a block diagram showing another embodiment of the present invention, in which parts equivalent to those in FIG. 1 are designated by the same reference numerals. In this embodiment, a single signal generator 14 is provided as a signal source for the speakers 11L and 11R, and the source signal emitted from this signal generator 14 is transmitted to a selector switch 19.
is applied independently to each speaker by switching.

On the other hand, the output of the microphone 13L or 13EL is supplied to the storage/arithmetic unit 22 via the microphone amplifier 2OL or 2OR and the changeover switch 21 and is temporarily stored, and the output of the left and right speakers IIL, IIB and the microphone 13L,
When the measurement is completed for 13R, microphone 1
The storage/arithmetic unit 22 calculates the root mean square value of each of the output values of 3L and 13R.

As a result, the second speaker 1. This is equivalent to calculating the average power from I L and 11 R as one transfer function.

FIG. 4 is a block diagram showing still another embodiment of the present invention, in which parts equivalent to those in FIG. 1 are designated by the same reference numerals. In this embodiment, signals with clear amplitude frequency characteristics such as warp tone, pure tone sweep, and impulse are used as the source signals for the speakers 11L and 11R, and the speakers ILL and 111% are driven with a time difference between each channel. In particular, it is configured to measure acoustic characteristics.

That is, for example, the impulse output from the signal generator 14 has its transfer function corrected by the transfer function correction device 15, and
First, the speaker 1. It is applied to IL to drive the speaker. The sound emitted from the speaker 11L propagates while being influenced by the sound field, and is received by the microphones 13L and 13R. The respective outputs of the microphones 13T, . Next, by switching the selector switch 19 to the R channel side, the R channel side is also connected to the speaker 11. R is driven, and the microphone 13
Each output of L and 13 R is added to the storage device 23 after addition processing.
is memorized.

Here, since the source signals of the speakers IIL and IIR have a time difference when they are driven, there is no correlation between each channel, as in each of the embodiments described above. Storage device 23
The two signals stored in are added by the arithmetic device 17, and the result of the addition is displayed on the display device 18.

As described above, according to each of the embodiments described above, the microphone l attached to both ears of the dummy mannequin 12 having a real human body configuration.
By calculating the average or power average of the outputs of 3 L and 13 R, the characteristics of the sound field can be treated as one transfer function. Therefore, the transfer function correction devices 15, 15T, inserted into the electric circuit of the reproduction system,
15R, by performing sound field correction on the one transfer function described above, it becomes possible to perform correction that is highly consistent with auditory sensation.

In each of the above embodiments, a stereo sound device using two-channel signals has been described. However, in a four-speaker playback device in which speakers are installed in the front and rear, single channels of L channel and R1 channel are respectively installed in the front and rear. It is also possible to obtain a signal addition between the front and rear of the L channel, the front of the R-F channel,
It is clear that even if an in-phase signal is applied between the rears and measured, the same effect can be obtained when the reproduction of the actual source is considered.

Furthermore, in each of the above embodiments, it was assumed that the sum of the outputs of the microphones attached to both ears was obtained by calculation, but it is clear that it can also be obtained by numerical calculation after analog processing and digital conversion. . When applied to an automatic graphic equalizer, the transfer function correction device 15, 1 is used via a microcomputer, etc.
This can be easily realized by feeding back to 5L and 15R.As described in detail of the invention, according to the acoustic characteristic measuring device according to the present invention, it is possible to easily achieve this by providing feedback to 5L and 15R. Since the acoustic characteristics are measured based on the output of the microphone, it is possible to perform accurate sound field evaluation that matches the auditory sensation.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a frequency characteristic diagram showing the sound absorption power of a real adult human body when wearing clothing, and Fig. 3 is a block diagram showing another embodiment of the present invention. Figure 4 is a block diagram showing still another embodiment of the present invention, Figure 5 is a block diagram showing still another embodiment of the present invention.
The figure is a block diagram showing a conventional example. Explanation of symbols of main parts

Claims (5)

[Claims] (1) Acoustic characteristic measurement that measures the acoustic characteristics between a sound source and a listening point that listens to the reproduced sound from the sound source in a stereo sound reproduction system that includes a plurality of sound sources provided corresponding to a plurality of channel signals. The apparatus is characterized by comprising a measurement system having a microphone attached to the ear of a real human body, a dummy mannequin, or a dummy head located at the listening point, and measuring acoustic characteristics based on the output of the microphone. Acoustic characteristics measuring device. (2) A pair of left and right microphones are provided, and the acoustic characteristics are measured by calculating an average of the respective outputs or an average of the power. Characteristic measuring device. (3) The electric circuit of the stereo sound reproduction system is provided with a correction device for correcting the overall transfer function, and the correction device is controlled directly or indirectly based on the measurement results of the acoustic characteristics. An acoustic characteristic measuring device according to claim 1 or 2. (4) With respect to the source signal that drives the plurality of sound sources,
2. The acoustic characteristic measuring device according to claim 1, further comprising signal processing means for performing signal processing so that each channel is uncorrelated with each other. (5) The acoustic characteristic measuring device according to claim 4, wherein the signal processing means performs temporal processing during measurement.