JPH0237971B2 - ONBAHYOKAKEISOKUKI - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a measuring instrument that can convert and output the acoustic characteristics of a sound field in which music is listened to, into physical quantities and psychological quantities that are easy to evaluate. Research has been conducted on desirable sounds and sound fields, but the research conducted this time revealed that the following parameters are necessary to determine a good sound field in a concert hall, which is the standard for the sound reproduced by acoustic equipment. It gradually became clear that there was something to show for it. In other words, there are four important objective parameters that represent the characteristics of binaural sound: audible sound pressure, delay time of first reflected sound, reverberation time of subsequent reverberant sound, and interaural cross-correlation coefficient. That is, the preference (auditory comfort) in a series of simulated sound fields.
This was clarified by a test. Next, the above four elements will be explained in detail. First, Figure 1 shows the relationship between a sound source and a person's head in a space with reflective walls. In the figure, 11 is a human head, 12 is a sound source, and 13 and 14 are reflecting walls. Here, the sound source signal is p(t), and the impulse responses from the sound source to the left ear and right ear are h _l (t) and h∫(t), respectively.
Then, the left ear and right ear signals f _l (t) and f _r
(t) is fl(t)=∫ ^t _p p(ν)h _l (t-ν)dν=p(t)*h
_l
(t) ...(Formula 1a) fr(t)=∫ ^t _p p(ν)h _r (t-ν)dν=p(t)*h
_r
(t) ... (Equation 1b) It is expressed as follows. The * mark in the above formula indicates composition. In the figure, n=0 of h _on means that the sound directly enters the ear, n=1 means that the sound reflected by the reflective wall 13 enters the ear, and n=2 means that the sound reflected from the reflective wall 14 enters the ear. m=l indicates the case where the sound enters the left ear, and m=r indicates the case where the sound enters the right ear. By the way, in FIG. 1, the reflecting walls 13, 14
The number of sounds that enter the ear after being reflected by the walls is shown only two for one reflecting wall, but assuming that many such reflections occur, the impulse response when reflected at the reflecting walls 13 and 14 is written as W _o (t ), the impulse responses reaching the left and right ears hl(t), h _r
(t) is h _l (t) = _∞ 〓 ⁿ⁼⁰ G _o W _o (t-△t _o ) * h _ol (t) ... (Equation 2a) h _r (t) = _∞ 〓 ⁿ⁼⁰ It can be expressed as GnW _o (t−△t _o )*h _or (t) (Formula 2b). This (Equation 2a) and (Equation 2b)
Using (Equation 1a) and (Equation 1b) above, fl (t) = _∞ 〓 ⁿ⁼⁰ p (t) * G _o W _o (t-△t _o ) * h _ol ... (Equation 3a) ) fr(t)= _∞ 〓 ⁿ⁼⁰ p(t)*G _o W _o (t-△t _o )*h _or ... (Formula 3b). Here, if the sound source p(t) does not have uniform radiation characteristics, p(t) can be replaced by p _o (t), taking into consideration the radiation pattern for each direction. By the way, the information in the acoustic signal that enters both ears includes independent and objective acoustic parameters, and the first parameter is the sound source signal p.
(t) can be given. Using the sound source signal, the long-term autocorrelation function ΦP(τ) is calculated as Φp(τ)=lim T→∞1/2T∫ ^T _-T p′(t)p′(t+τ)dt... 4) It can be expressed as Here p'(t)=p(t)
*s(t), where s(t) corresponds to the sensitivity of the ear,
Theoretically, it is expressed by the characteristics of the middle ear and the outer ear, but in practice it can be expressed as the impulse response of a G filter, which is well known as an approximation of auditory characteristics. Naturally, the power Φp of p′(t)
By dividing (Equation 4) by (o), the normalized autocorrelation function φp(τ) is obtained as φp(τ) = Φp(τ)/Φp(o)...(
Equation 5) can be expressed as: FIGS. 2a and 2b illustrate the measured values of the normalized autocorrelation function corresponding to the above (Equation 5).
FIG. 2a shows the measured values corresponding to the music "Royal Pavane" by Gibbons, which is hereinafter referred to as phonology A. Figure 2b is the music “Sinho Nietsta” by Arnold, Op.
48: Movement, Allegro con brio (Synfornietta, Opus48: Movement,
This acoustics is referred to as music B hereafter.Next, the second objective parameter is the impulse generated by reflection at boundaries such as walls. This is related to the initial time delay between the direct sound and the first reflected sound, as well as the initial reflected sound, subsequent reverberation, and changes in the spectrum due to reflection. Objective parameters of 3 include the impulse responses h _ol (t) and h _or (t) to the left and right ears.These impulse responses play an important role in sound localization and are independent of each other. This is clear from the fact that in the case of a centrally localized signal, h _ol (t) h _or (t). Next, the impulse responses of these two h _ol (t) and h _or
Derive the mutual dependency between (t). First, we define the long-term interaural correlation function Φ _lr (τ) between the binaural signals fl(t) and fr(t) as fl(t) and fr(t).
When expressed using Φ _lr (τ)=lim T→∞1/2T∫ ^T _-T f _l (t) fr (t + τ) dt, |τ|≦|ms (Equation 6). By the way, a sense of spaciousness or a sense of no direction occurs when the interaural cross-correlation is a small value, and in the case of only signals from a fixed direction, the interaural cross-correlation is The cross-correlation function has a large peak. Here |τ|<1ms
This is because the time difference between the binaural signals fl(t) and fr(t) is, from the relationship between the binaural distance and the speed of sound,
This is because the time normally cannot exceed 1 ms. First, the interaural cross-correlation function Φ ^(o) _lr (τ) with only direct sound is fl (t) = p (t) * h _pl (t), f _r (
t)=p
It can be obtained by substituting (t)*h _pr (t) into (Equation 6). By the way, the normalized autocorrelation function φ ^(o) _lr (τ) for only the direct sound is It can be expressed as Note that φ ^(o) _l r(τ) is temporarily h _pl
If (t) h _pr (t), it becomes approximately 1. Here Φ ^(o) _ll
(o) and Φ ^(o) _rr (o) show the τ=0 autocorrelation function of the signal at the left and right ears, respectively. Next, if another reflected sound is added to the direct sound after the time when the autocorrelation function of the direct wave becomes small, then the normalized autocorrelation function φ ^(N) _lr (τ) is W _o (t )
is equal to the Dirac delta function δ(t), then It is expressed as Here, Φ ⁽ⁿ⁾ _lr (τ) is the interaural interaction function of the n-th reflex as Φ ⁽ⁿ⁾ _ll (o), Φ ⁽ⁿ⁾ _rr (o)
represents the autocorrelation function at τ=0 of the nth reflected sound of the left and right ears, respectively. Note that when the sound source is in front of the user in a normal room, the maximum value of the interaural cross-correlation function is obtained extremely close to τ=0. By the way, the strength of the normalized interaural cross-correlation is
IACC as IACC = |φ _lr (τ) | max, for | τ | 1ms
...(Formula 9) is defined as follows. Note that φl _r (τ)=Φ _lr (τ)/√ _ll
(o) Φ _rr (o), and Φ _ll (o) and Φ _rr (o) respectively indicate the autocorrelation functions at τ=0 of the signal tones for the left and right ears. The above describes the long-term autocorrelation function of the sound source signal, the multiple impulse responses caused by sound reflecting off walls, etc., and the interaural cross-correlation function that indicates the correlation between binaural signals. However,
Next, from these physical quantities, we can determine four elements that are important objective parameters that represent the characteristics of binaural sound signals: audible sound pressure, delay time of the first reflected sound,
We will discuss how to find the optimal values for the reverberation time of the subsequent reverberant sound and the value of the interaural correlation function. The results of the preference test conducted using the aforementioned music A and music B are shown in FIGS. 3a and 3b.
The horizontal axis is IACC, and the vertical axis is audible sound pressure (unit, dBA). The listening sound pressure can be considered to be the value of τ=0 of the autocorrelation function, and the value on the horizontal axis of the graph indicates the preference. From Figures 3a and b, it is clear that the optimal listening sound pressure [p] _p does not depend much on IACC; it is 77 to 79 dBA for music A with a rather slow tempo, and 79 dBA for music B with a fast tempo. teeth
It can be seen that it is 79-80dBA. It can be seen that the optimal value of the listening sound pressure is around 79 dBA in both cases. Next, according to the results of evaluating a synthesized sound field consisting of a direct sound and a single reflected sound when reproduced by a speaker using music and speech, it is found that the normalized autocorrelation function φ _p (τ) of the sound source signal is When the reflected sound level is varied by ±6 dB of the direct sound, the optimal delay time of the reflected sound is |Φ _p (τ)| is 1/10 of the first reflected sound level G ₁ It has become clear that the period corresponds to that time. There｜
The horizontal axis is the time τd at which Φ _p (τ) | corresponds to 1/10 of the level C ₁ of the first reflected sound, and the vertical axis is the delay time [△t ₁ ] _p of the single reflected sound at which the preference is maximum. FIG. 4 is a diagram showing the axis. The range shown in the figure indicates the delay time when it is 0.1 lower than the maximum value of the preference, and the symbol ○ in the figure indicates the delay time when the preference is 0.1 lower than the maximum value.
Reflected sound level G ₁ = 6 dB, ● is G ₁ = 0 dB, □ is
Each figure shows the case when G ₁ = -6 dB. In particular, if τ _p is the time during which |Φ _p (τ) becomes 0.1 times Φ _p (o), when G ₁ =0 dB, it can be expressed as τ d = τ _p . Note that the τ _p of music A and B mentioned above are 127 ms and 35 ms, respectively, as can be inferred from Figure 2 a and b.
As is clear from Figure 4, a straight line can be drawn to approximate each point in the figure, and when looking at both axes corresponding to the straight line, τd is the single reflection with the maximum preference. It can be seen that the sound delay time [△t ₁ ] almost matches _p . At the same time, it almost coincides with the time τ _p when |Φ _p (τ)| becomes 0.1 times Φ _p (o).
That is, if this is expressed mathematically, the most preferable delay time [Δt ₁ ] _p of the first reflected sound can be expressed as [Δt ₁ ]p=τ _p (Formula 10). In addition, when τ>τ _p , |φ _p (τ)|≦KG ^c ... (Formula 11), and in this case K=const (=0.1), C=const (=
1.0),

[Formula]. When using the normalized autocorrelation function Φ _p (τ), the above (Equation 11) becomes |Φ _p (τ)|≦0.1 when τ>τ _p
...(Formula 12) Furthermore, the autocorrelation function of the sound source signal has a close relationship with the optimal reverberation time, and this relationship is shown in FIG. The vertical axis is the optimal reverberation time of the subsequent reverberant sound [Tsub]
_p , and the horizontal axis is τ _p . The reverberation time referred to here is not expressed as the time for the direct sound to attenuate by 60 dB, but as the time for the signal in the reverberation section to attenuate by 60 dB. In the figure, music A and music B are the same as those mentioned above, but music E is Mozart.
``Symphony in C major K, 551 Jupiter 4th movement, molto allegro'', and Speech S is ``Symphony in C major K, 551 Jupiter 4th movement, molto allegro'', and Speech S is Doppo Kunikida's ``Sound of the Tone River'', ``I'm surprised at how blue the sky is, how bright and high it is.'' (τp =12ms)
It is. As is clear from the figure, the relationship shown in FIG. 5 can be approximately approximated by the relationship [Tsub]p≈(23±10)τp. Next, Figure 6 shows the results measured in a synthetic sound field consisting of a direct sound and a single reflected sound, where the horizontal axis represents the arrival direction ξ of the reflected sound, and the vertical axis represents the normalized Preference and IACC values are shown. It can be seen from FIG. 6 that the preference increases as the value of IACC decreases. That is, the correlation function between the preference score and the IACC value is negative (-0.76: 1% significance level), and this holds true when IACC takes the maximum value at τ = 0. . It can also be read from the figure that the most effective way to reduce IACC is to make the early reflected sound arrive within a range of ± (55° ± 20°) from the front. Next, a preference measure using the above four parameters will be described. Incidentally, this scale of preference was determined through a comparative test, and each parameter independently influences the scale of preference. As a result, since the principle of superposition can be applied, it becomes possible to generalize sound field preference data obtained in concert halls etc. by normalizing each objective parameter by its optimal value. . The preference scale obtained in the comparative test will be explained below. First, a measure of preference S ₁ as a function of listening sound pressure is shown in FIG. In this figure, the scale at optimal hearing sound pressure is set to zero. S ₁
The values of are almost symmetrical around the most preferable listening sound pressure (0 dB), but the preference scale is slightly lower when the listening sound pressure is lower than when the listening pressure is lower than when the sound pressure is higher. There is a good trend. If this is expressed mathematically, S ₁ (LL)≦S ₁ (−LL) (Formula 13). Here, LL=20log(p/[p] _p ), p is the audible sound pressure, and [p] _p is the optimal audible sound pressure. Note that in the figure, ○ indicates the value of music A, and X indicates the value of music B. Next, the measure S ₂ of preference as a function of the delay time between the direct sound and the first reflected sound (first reflected sound delay time) is shown in FIG. The horizontal axis of this figure is normalized by the most preferred time delay [Δt ₁ ] _p . By the way, the delay time of the second reflected sound is known to have an optimal value [△t ₂ ] _p of [△t ₂ ] _p 1.8τ _p . This optimal value was used as the delay time of reflected sound. Of course, it goes without saying that the condition of (Equation 10) exists. In the figure, ○, a, A, and △ are individual measurement results for music A, and X, b,
Each of B and △ is an individual measurement result using music B, C is music C, D is music D, □ is music E,
● is the measurement result by Speech S. Music A,
I have already mentioned B and E earlier, but music C is Haydn's Symphony No. 102 in B flat major, second movement Adagio (τp = 65ms), and music D is Wagner's Siegfried.
Idyll) 332 bars (τ _p = 40 ms). Furthermore, the 6th
As in the figure, the optimal delay time scale for the first reflected sound is set to zero. Furthermore, the preference scale S ₃ as a function of the reverberation time of the subsequent reverberant sound is shown in FIG. In the figure, the solid line is the total sound pressure of reflected sound.

It is the measure of preference S ₃ as a function of the reverberation time of the subsequent reverberant sound in the case of [Equation], and the dashed line is that for the case of G=1.1. In the figure, ○ and a are experimental results for music A, X and b for music B, □ for music E, and ● for speech S, all of which are for the case of G=4.1. G=4.1 corresponds to a case where there is a lot of reverberant sound, such as when being at the rear of a concert hall, and G=1.1 corresponds to a case where there is a lot of direct sound, such as at the front seats of a hall. The preference scale at the most preferred reverberation time is set to zero. Next, the preference measure S ₄ as a function of IACC is shown in FIG. In the diagram, ○ is music A
When , X, b are the experimental results for music B. Due to the nature of IACC, if the maximum value is taken at τ=0, the sound image is in the front direction. As is clear from the figure, as IACC approaches 1, the preference measure S ₄ decreases rapidly. Therefore, it is necessary to make IACC smaller than 0.5 as much as possible. So far, four scales of preference S ₁ to
Although up to _S4 has been described, these four scales can be approximated by the approximate expressions shown below. First, the hearing sound pressure preference ^scale S ₁ shown in Fig _. 7 is _{S 1} = −α _{1 |} )
...(Formula 15) In addition, α=0.07±0.03, X ₁ >0 0.04±0.02, X ₁ <0 ... (Formula 16) Next, the measure of preference S ₂ for the delay time of the first reflected sound shown in Fig. 8 is S ₂ = −α ₂ |X ₂ | ^3/2 (Formula ₁₇ ) However, it can _be expressed _{as :} Note that α ₂ =1.42±0.6, X ₂ >0 1.11±0.5, X ₂ <0 (Formula 19). Furthermore _, the scale S ₃ of the preference of the reverberation time of _the subsequent reverberant sound shown in FIG. 9 is S ₃ ⁼ −α ₃ | Tsub]) _p )... (Equation 21) In addition, α ₃ = (0.74±0.25)G+ (0.45±0.15), X ₃ >0 − (0.42±0.14 ₎ G+ (2.36±0.79), 22), when α ₃ is negative, α ₃ =0 (Formula 22'). _The remaining IACC preference measure S ₄ shown in FIG ^. 10 can be expressed as S ₄ = _{−α 4} . Note that α ₄ =1.45±0.44 (Formula 25). Based on the principle of superposition, the overall measure S of preference in a concert hall or the like can be expressed as S= ₄ 〓 ⁱ⁼⁰ Si (Formula 26). Of course, S _i (i=1,
2, 3, and 4) indicate the four preference scales mentioned above. By using the preference scales S and S _i (i=1, 2, 3, 4) obtained in this way, it is possible to accurately evaluate the sound field. This invention uses four parameters to measure preference in a concert hall or room: audible sound pressure in the sound field, delay time of the first reflected sound, reverberation time of the subsequent reverberant sound, and interaural cross-correlation coefficient. The object is to provide a measuring device with which individual preference measures and overall preference measures can be determined. (1) Sound field evaluation measuring instrument of the present invention Hereinafter, one embodiment of the sound field evaluating measuring instrument of the present invention will be described with reference to the drawings. FIGS. 11 and 12 are block diagrams showing the general structure of a sound field evaluation measuring instrument according to the present invention. FIG. 12 is a block diagram showing each of the four parameters. In the figure, 1 is a human head or dummy head, 2l, 2r are microphones inserted into the entrance of the external auditory canal, 3, 3l, 3r are preamplifiers, 4 is a physical quantity analyzer, 5 is a comparator,
6 is a psychological quantity converter, 7 is a comprehensive evaluator, 8 is a preference output terminal, 9 is a recorder for recording preferences, 10 is a sound field evaluation measuring device, 40 is an adder, 41 is audible sound pressure analysis vessel, 4
2 is a first reflected sound delay time analyzer, 43 is a subsequent reverberation sound reverberation time analyzer, 44 is an interaural cross-correlation function analyzer, 51 is a listening sound pressure psychological quantity converter, 52
is a first reflected sound delay time psychological quantity converter, 53 is a subsequent reverberation sound reverberation time psychological quantity converter, 54 is an interaural cross-correlation coefficient psychological quantity converter, y, y ₁ , y ₂ , y ₃ ,
_y4 is a comparison data input terminal. The respective optimum values are input to the comparison data input terminals y, y ₁ , y ₂ , y ₃ , y ₄ , and a signal corresponding to the optimum hearing sound pressure ([p] _p ) is input from the input terminal y ₁ . However, from input terminal y ₂ , the optimal first reflected sound delay time ([△t ₁ ] _p )
A signal corresponding to the optimal subsequent reverberant sound reverberation time ([Tsub] _p ) is input from the input terminal y ₃ , and a signal corresponding to the optimal interaural cross-correlation coefficient is input from the input terminal y ₄ . do. It should be noted that the hearing sound pressure analyzer 41 and the first
The reflected sound delay time analyzer 42, the subsequent reverberant sound reverberation time analyzer 43, and the interaural correlation function analyzer 44 correspond to a physical quantity analyzer corresponding to the physical quantity analyzer 4 in FIG. Hearing sound pressure psychological quantity converter 51 and first reflected sound delay time psychological quantity converter 5 in FIG.
2. The subsequent reverberation sound reverberation time psychological quantity converter 53 and the interaural cross-correlation coefficient psychological quantity converter 54 are the comparison and psychological quantity converting sections corresponding to the comparator 5 and the psychological quantity converter 6 in FIG. Equivalent to. Similarly, the comprehensive evaluator 7 corresponds to a comprehensive evaluation section. First, a simple flow of an embodiment of the sound field evaluation measuring device of the invention will be explained using FIG. 11.
First, a sound field is evaluated and a dummy head or head 1 is installed in a location such as a concert hall or listening room. The sound pressure signals of both ears are detected by the microphones 2l and 2r installed at the entrances of the left and right external auditory canals, amplified and added by the preamplifier 3, and then processed by the physical quantity analyzer 4. From the sound pressure signals of both ears, the physical quantity, that is, the audible sound pressure,
The first reflected sound delay time, the subsequent reverberant sound reverberation time, and the interaural cross-correlation coefficient IACC are determined, and the respective values are compared with the respective optimal values input as comparison data from the input terminal y in the comparator 5. , then the already explained (Equation 14) (Equation 17)
The psychological quantity converter 6, which performs processing based on (Equation 20) and (Equation 28), converts it into a psychological quantity, that is, a quantity corresponding to the preference, and then comprehensively evaluates it in the comprehensive evaluator 7 to determine the preference in the sound field. This measuring instrument, which is output from the output terminal 8, can be used to evaluate the sound field of a concert hall or listening room. Next, the embodiment shown in FIG. 11 will be explained in detail with reference to FIG. 12, which shows the flow of four individual parameters. As mentioned above, the sound pressure signals detected from the microphones 2l and 2r are transmitted to the preamplifiers 3l and 3r.
After being amplified by and added by an adder 40,
an audible sound pressure analyzer 41 corresponding to a physical quantity analysis section;
It is input to each of the first reflected sound delay time analyzer 42 and the subsequent reverberant sound reverberation time analyzer 43, and in each analyzer, the audible sound pressure p, the first reflected sound delay time Δt ₁ , and the subsequent reverberant sound reverberation time Tsub are input. Each is analyzed, measured, and output. Also, these 3
Apart from the two flows, the outputs from the two preamplifiers 3l and 3r before being added by the adder 40 are
The maximum value of the binaural cross-correlation coefficient is input to the binaural correlation function analyzer 44, which corresponds to the physical quantity analysis unit.
IACC is parsed and output. Next, four analyzers 41, 42, 4 corresponding to the physical quantity analysis section are
The audible sound pressure p, first reflected sound delay time Δt ₁ , subsequent reverberation sound reverberation time Tsub, and maximum interaural cross-correlation coefficient IACC output from each of It is input to the corresponding listening sound pressure psychological quantity converter 51, first reflected sound delay time psychological quantity converter 52, subsequent reverberation sound reverberation time psychological quantity converter 53, and other comparison data input terminals.
Optimal hearing sound pressure [p] _p input from each of y ₁ , y ₂ , y ₃ , and y ₄ , optimal first reflected sound delay time [△
t ₁ ] _p , the optimal subsequent reverberation sound reverberation time [Tsub] _p , and the optimal interaural cross-correlation coefficient are compared. The optimal binaural cross-correlation coefficient can be considered to be 0, but in practice
In many cases, there is no problem even if the value is set to 0.4 to 0.5 or less, so in this embodiment, it is set to 0.4. The calculation formula for this comparison and the psychological quantity conversion in the psychological quantity converting section is the hearing sound pressure psychological quantity converting section 5.
1, the above-mentioned (Equations 14) to (Equations 16), the first
The reflected sound delay time psychological quantity converter 52 uses the above-mentioned (Formula 17) to (Formula 19), and the subsequent reverberation sound reverberation time psychological quantity converter 53 uses the above-mentioned (Formula 20) to
(Formula 22'), interaural cross-correlation coefficient psychological quantity converter 5
In 4, (Formula 23) to (Formula 25) are as follows, and the preference scales S ₁ and S ₂ are the outputs obtained from this comparison and psychological conversion section.
, S ₃ and S ₄ can be obtained through calculation processing using a microcomputer program or the like. However, if accuracy is not a big issue, a conversion table as shown below may be used.

【table】

【table】

[Table] The above conversion tables are examples of conversion tables for the audible sound pressure psychological quantity converter 51 and the first reflected sound delay time psychological quantity converter 52, respectively. This conversion table contains the hearing sound pressure p, the optimal hearing sound pressure [p] _p , the first reflection delay time △t ₁ , and the optimal first
Preference scales S ₁ and S ₂ corresponding to the reflection delay time are stored. Although only the conversion tables for the audible sound pressure psychological quantity converter 51 and the first reflected sound delay time psychological quantity converter 52 are shown here, the following reverberation sound reverberation time psychological quantity converter 53 and the interaural cross-correlation coefficient psychological quantity converter 52 are shown. A similar conversion table can be created for the quantity converter 54 as well. The preference scales S ₁ to _{S 4} outputted from the converters 51 to 54 of the comparison and psychological quantity converter in this way are input to the comprehensive evaluator 7, and the overall result obtained as a result of the comprehensive evaluation is A preference measure S is output to the output terminal 8. This output is recorded on the recorder 9. However, although the recording device 9 is included in this embodiment, it is not necessarily necessary to include it, and it goes without saying that it may be omitted or may be replaced with a display device. Next, the audible sound pressure analyzer 4 of the physical quantity analysis section used in the sound field evaluation measuring instrument 10 in FIG.
1. An example of the configuration of each of the first reflected sound delay time analyzer 42, subsequent reverberant sound reverberation time analyzer 43, and binaural cross-correlation function analyzer 44 will be explained using FIGS. 13a to 13e. FIG. 13a shows the basic configuration of the first reflected sound delay time analyzer 42 or the subsequent reverberant sound reverberation time analyzer 43 using a square integral type reverberation meter by MR Schroeder, which is a modified correlator. It has the function of the listening sound pressure analyzer 41 that also includes an output corresponding to sound pressure. FIG. 13b shows an example of a priority encoder used to output a code corresponding to the first reflected sound or reverberation time of the first reflected sound delay time analyzer 42 or the subsequent reverberant sound reverberation time analyzer 43. It is a diagram. FIGS. 13c and 13d are diagrams showing other configuration examples of the audible sound pressure analyzer. FIG. 13e is a diagram showing an example of the configuration of a circuit for calculating the interaural cross-correlation coefficient. In FIG. 13a, 400 is an input terminal of a circuit used as a first reflected sound delay time analyzer or a subsequent reverberant sound reverberation time analyzer using a square integral reverberation meter, 401, 402, and 403 are delay circuits; 404-411 are multipliers, 412-4
15 is an integrator, 416 to 418 are adders, 41
9 to 421 are comparators, 422 is an output terminal for the autocorrelation coefficient φ ₀ , and 423 to 425 are O ₁ to O _{o-1 output terminals that output information on the delay time of the first reflected sound or the reverberation time of the subsequent reverberant sound, respectively.} Output terminal, 42
6 is an attenuator, and in FIG. 13b, 430 is O ₁ to output from output terminals 423 to 425.
O _o-1 input priority encoder,
x ₁ to _{x o-1} are code outputs corresponding to the first reflected sound delay time or the subsequent reverberant sound reverberation time. In FIGS. 13c and d, 435 is a rectifier circuit, 436 is a reduction pass filter, 437 is a multiplier, In FIG. 13e, 441 is an input terminal into which the left input signal Lin of the circuit for calculating the interaural cross-correlation coefficient is input, 442 is an input terminal into which the right input signal Rin is also input, 443 and 444 are adders, and 445 to 4
48 is a root mean square circuit RMS, 449 is an arithmetic circuit,
450 is an output terminal that takes out an output corresponding to the cross-correlation coefficient. In the circuit of FIG. 13a, each of the delay circuit, adder, and comparator is (n-1).
The output signal from the delay circuit is input to the multiplier, the integrator is input, and the output signal from the integrator is input to the multiplier and output terminal. Three representative objects are shown, and only four representative objects are shown.The rest are omitted, and consecutive symbols are given to the objects shown in the figure. Therefore 2
The (n-1)th delay circuit 403 next to the (n-1)th delay circuit 402, and the third to (n-2)th delay circuits are not labeled for convenience. First, FIG. 13a will be explained. When a signal is applied to input terminal 400, the input signal is applied to multipliers 404 to 407 and also to delay circuit 401. Delay circuit 401
The output is given to the multiplier 405 and also given to the next delay circuit 402 to produce successively delayed signals up to the output of the (n-1)th delay circuit 403. Each delay circuit 401-40
The outputs of 2 are multiplied by multipliers 405-407. Multiplier 404 performs a square operation on the input signal itself. Next, the multiplier 404
~407 output signals are respectively integrators 412~
The output signal is integrated at 415 and further squared by multipliers 408-411. Note that the output signal of the integrator 412 is output as is to the terminal 422, apart from being input to the multiplier 408. This signal is an autocorrelation coefficient φ(o), that is, the square of the power of the input signal, and contains information corresponding to the sound pressure signal. The processing of squaring the power can also have an equivalent function simply by converting it into an absolute value. By the way, the output signals of the multipliers 408 to 411 are the square of the autocorrelation coefficient φ ² _p ,
² ₁ , ..., φ ² _o-1 signals are sent to adders 416 to 418
The outputs of adders 416 to 417 are added to the next adder, respectively, up to the (n-1)th adder 418. By the way, the output signal from the multiplier 408 and the adders 416 to
The output signal from 417 is the last adder 4 in comparator circuits 419 to 421, respectively.
The output signals of 18 are compared with the signals after being attenuated by an attenuator 426, and the respective output signals O ₁ - 423 - O _o-1 425 are output to the output terminals 423 - 425.
Output. Note that the attenuation ratio of the attenuator 426 is the first
When calculating the reflected sound delay time, (0.1) ² is used.
When determining the subsequent reverberation sound reverberation time, the value set to (0.001) ² is used. This is similar to what is already known as an optimal delay time detector, and is used to find the delay time at which the value of the autocorrelation function becomes 1/10 or 1/1000. Also, from the delay circuit 401 to the delay circuit 4
The total delay time up to 03 is required to be about the length of the first reflected sound delay time and the subsequent reverberant sound reverberation time, that is, about 100 to 200 ms and 3 to 5 seconds, respectively. Naturally, as this time elapses, the integrating circuits 412-415 need to be reset. However, the reset circuit is not shown. Next, the priority encoder 430 shown in FIG. 13b is connected to the comparator 4 shown in FIG. 13a.
19~421 output signal O ₁ 423~ _{O o-1} 42
5, and the delay time τ (=τ _p ) corresponding to the attenuation ratio (0.1) ² or (0.001) ² of the attenuator 426 in FIG. ₁ code corresponding to time)...
x Display or output _o-1 . The following Figures 13c and d are diagrams showing other examples of circuits used as audible sound pressure analyzers, and in this case as well, the output signal φ ₀ is obtained from the output terminal 422 in Figure 13a , you can know the audible sound pressure. This configuration is a combination of a low-pass filter 436 and a rectifier circuit 435 or a square multiplier 437, as shown in FIG. 13c. A circuit 519 for determining the interaural cross-correlation coefficient shown in FIG. 13e uses an example of a circuit system for determining the normalized correlation coefficient. First, input terminal 4
When the input signal Lin is input from 41 and the input signal Rin is input from the other input terminal 442, the input signals Lin and Rin directly enter the root mean square circuits 445 and 448, respectively, and output their respective root mean square values γ and δ. be done. Also the input signal
The sum signal between Lin and Rin is output from the adder 443,
The difference signal is taken out from an adder 444 that makes one signal negative and adds it to the other signal, and inputs it to root mean square circuits 446 and 447, and similarly, the sum signal and the difference signal are converted to respective root mean square values α and β.
Output. The four root mean square value signals α, β, γ, and δ thus obtained are sent to the calculation circuit 44.
9, the calculation process is (α ² − β ² )/(4γδ)
As a result, an output φ _lr (o) corresponding to the cross-correlation coefficient, that is, an interaural cross-correlation coefficient (IACC) is obtained at the output terminal 450. However, when using the circuit shown in FIG. 13e, the input signals Lin and Rin are 0 to 1
If a delay circuit of ms is provided, the delay time is varied, and the maximum value is determined, the circuit configuration corresponds to the above-mentioned (Equation 9), and a value faithful to (Equation 9) can be obtained from that circuit. It will be done. A delay circuit for this purpose is not shown in FIG. 13e. Note that in order to calculate the interaural cross-correlation coefficient (IACC) with higher accuracy, numerical calculations may be performed using the above-mentioned equations (7) to (9). In the embodiment described so far, the inputs to the audible sound pressure analyzer 41, the first reflected sound delay time analyzer 42, and the subsequent reverberation sound reverberation time analyzer 43 are input to the dummy head or the left and right ears of the human head 1. Although the sum signal of two incoming acoustic signals has been used, the delay time between the two signals is usually less than 1 ms, and these three decomposers 4
Since there is no large difference in the analysis results of Nos. 1 to 43, sufficient analysis results can be obtained even if one of the left and right acoustic signals is used.
In the embodiment of the first invention described above, the optimum audible sound pressure [p] _p of the sound field evaluation measuring instrument 10 varies depending on the type of sound source, but it is approximately (79±5). Since it is about dB, 79 dB is used here as a representative. Also, the optimal first
Reflected sound delay time [△t ₁ ] _p and optimal subsequent reverberant sound reverberation time [Tsub] _p are the delay time τ that first becomes smaller than the attenuation ratio by the first reflected sound delay time analyzer 42 from the actual sound source itself. It is best to find _p and use it as the optimal first reflected sound delay time [△t ₁ ] _p , or multiply it by (23±10) and use it as the optimal subsequent reverberation sound reverberation time [Tsub] _p . In this example, [Tsub] _p =23τ _p was used. As described above, the sound field evaluation measuring instrument of the present invention includes one or two microphones, an amplification device for amplifying the acoustic signal obtained from the microphone, and an amplification signal that can be heard from the amplified signal. sound pressure p
audible sound pressure measuring means for measuring the audible sound pressure, and a first reflected sound delay time measuring means for measuring the first reflected sound delay time Δt ₁ from the amplified signal; Reverberation sound reverberation time Tsub
a subsequent reverberation sound reverberation time measuring means for measuring the reverberation time; furthermore, a binaural cross-correlation coefficient measuring means for measuring the interaural cross-correlation coefficient IACC from the amplified signal; Optimum hearing sound pressure [ _p ] If the above hearing sound pressure is greater than the optimal hearing sound pressure, - (0.07 ±0.03),
When it is small, the value obtained by multiplying by -(0.04±0.02) is output as the preference (psychological quality in terms of hearing) S ₁ , that is, the above (Equation 14)
A first comparison conversion means that outputs an output corresponding to ~(Equation 16), and a ratio of the first reflected sound delay time △t ₁ and the optimum first reflected sound delay time [△t ₁ ] _p to the base of 10. If the first reflected sound delay time is larger than the optimal first reflected sound delay time, set -(1.42±0.6) to the value of the absolute value of the logarithm to the 3/2 power, and if it is smaller, set -(1.11±0.5) to the value. The second function outputs the multiplied value as the preference measure _S2 , that is, outputs corresponding to the above (Equation 17) to (Equation 19).
Comparison conversion means and the above subsequent reverberant sound reverberation time
The value is the 3/2 power of the absolute value of the logarithm to the base 10 of the ratio between Tsub and the optimal subsequent reverberation sound reverberation time [Tsub] _p .
When the reverberation time of the subsequent reverberant sound is larger than the optimal reverberation time of the subsequent reverberation sound, the sum of -(0.74±0.25) times the sound pressure of the entire reflected sound and -(0.45±0.15) is used; Preference scale _S3 In other words, the third function outputs the output corresponding to (Equation 20) to (Equation 22') above.
and outputs the value obtained by multiplying the value of the 3/2 power of the above-mentioned interaural cross-correlation coefficient by -(1.45±0.44) as the preference measure _S4 , that is, the above-mentioned (Equation 23) ~ Comprehensively evaluates the preference scales S ₁ , S ₂ , S ₃ , and S ₄ output from the fourth comparison conversion means that outputs the output corresponding to (Equation 25) and the first to fourth comparison conversion means. Since the present invention is provided with comprehensive evaluation means for outputting the overall scale S of the preference, it is possible to perform an accurate and faithful sound field evaluation. (2) Application example of the present invention Next, based on the four physical parameters of the audible sound pressure in the sound field, the delay time of the first reflected sound, the reverberation time of the subsequent reverberant sound, and the interaural cross-correlation coefficient, DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of each of a first and second acoustic device to which the present invention is applied, which can correct a sound field and create a more preferable sound field, will be described with reference to the drawings. (2-1) First acoustic device FIG. 14a is a configuration block diagram of an embodiment of the first acoustic device that can correct the sound field and create a more preferable sound field. 14b shows one example of the sound field expansion device included in the audio device of FIG. 14a, and FIG. 14c shows another example of the reverberation device included in the audio device of FIG. 14a. First, in FIG. 14a, 501 is the input terminal _INR , 502 is the input terminal _INL , 503a to
503d is an adder, 504a, 504b are reverberation devices, 505a, 505b, 505r, 5
05l is an attenuator, 506a and 506b are delay circuits, 507 is a scaler which is a type of frequency dividing circuit, 508a and 508b are up-down counters, 509 is a digital-to-analog converter, and 510a and 510c are first reflected sound delay times. Analyzer, 510b is a subsequent reverberation sound reverberation time analyzer, 511a to 551c are encoders, 5
12a, 512b, 513a, 513b are comparators; 514a, 514b, 514c are smoothing circuits; 515a, 515b are variable resistors for setting target values; 516 is a sound field expansion device; 517r, 517l drive speakers. Power amplifier for 518r, 518l
is a speaker, 519 is an interaural cross-correlation coefficient (IACC) calculator, 520 is a multiplier, 531,
532 are input terminals inr, inl, 5 from the reverberation devices 504a, 504b to the sound field expansion device 516.
21 is the CLOCK signal input terminal, 533, 53
4 is the output terminal outr of the sound field expansion device 516;
outl, 535 is an input terminal attm from the comparator 513b to the sound field expansion device 516. 1st
4b, 530a to 530d are adders, 536 is an attenuator, 537 is a low pass filter, 538 is a high pass filter, and 53
9 is a phase shift circuit or a delay circuit. In FIG. 14c, 504c is a reverberator made by MR Schroeder and BS Atal, 540a to 540i are adders, and 54
1a, 451b are phase inversion circuits, 542a,
542b is voltage follow, 543a~
543f is a delay circuit, 544a to 544f are attenuators, 545 is an input terminal of attenuator 504c, and 546 is an output terminal of attenuator 504c. Note that the same reference numerals in the drawings as those in other drawings indicate the same or corresponding parts. Next, the operation of one embodiment of the first acoustic device will be explained using FIGS. 14a, 14b, and 14c. First, an acoustic signal from a record, tape, microphone, radio, etc. is applied to the input terminals _INR 501 and _INL 502. This acoustic signal is sent to the adder 5
03c and input to the first reflected sound delay time analyzer 510c. This first reflected sound delay time analyzer 510c is constituted by the circuit 42 in FIG. 12 described above, that is, the same circuit as that shown in FIG. 13a. The damping ratio is set to 1/10 so that time can be measured. The output of this first reflected sound delay time analyzer 511 is input to the encoder 511, and the encoder 51
1 outputs an output [(Δt ₁ ] _p = τ _p ) obtained by setting the delay time [Δt ₁ ] _p of the first reflected sound that is optimal for the sound source as τ _p . This encoder 51
The output from 1c is input to the comparator 512a, and is also input to the multiplier 520, 23
Multiplied by optimal subsequent reverberation sound reverberation time [Tsub] _p
(=23°τ _p ) is applied to the comparator 512b. On the other hand, the signals coming into the dummy head placed in a sound field such as a listening room or the microphones 2r and 2l installed at the left and right ears of the human head 1 are amplified by preamplifiers 3l and 3r. , the outputs are added by an adder 503d, and then input to the first reflected sound delay time analyzer 510a, which is the same as 42 in FIG.
It is also input to b. The configuration of this subsequent reverberation sound reverberation time analyzer 510b is the same circuit configuration as that described at 43 in FIG. 12. Next, the first reflected sound delay time analyzer 510a
The output is input to the encoder 511a, and a signal corresponding to the delay time Δt ₁ of the first reflected sound after being affected by the sound field is obtained. Thereafter, it is input to the comparator 512a. Further, the output of the subsequent reverberation sound reverberation time analyzer 510b is input to the encoder 511b, and a signal corresponding to the subsequent reverberation sound reverberation time Tsub after being affected by the sound field is obtained, and this signal is sent to the comparator 5
12b. By the way, comparator 51
2a, the optimal first reflected sound delay time [Δt ₁ ] _p from the encoder 511c and the delay time Δt ₁ of the first reflected sound after being affected by the sound field from the encoder 511a are compared. , if the first reflected sound delay time △t ₁ is larger than the optimal first reflected sound delay time [△t ₁ ] _p , then in order to make the first reflected sound delay time △t ₁ smaller, , comparator 512a to counter 5
Give countdown signal CD to 08a,
The content of the counter 508a is made smaller, and therefore, in the scaler 507 that performs frequency division based on the content of the counter 508a, the value to be divided becomes smaller, and the value from the input terminal 521 becomes smaller.
DELAY obtained by dividing the CLOCK signal
The frequency of the CLOCK signal increases and
The reverberation circuit 504 is activated by the DELAY CLOCK signal.
The delay time of the delay circuits 506a and 506b formed by BBDs (bucketed bridge devices) in the circuits a and 504b is reduced.
However, if the optimal first reflection delay time [△
t ₁ ] If the first reflected sound delay time Δt ₁ is smaller than _p , a count-up signal CU is given from the comparator 512a to the counter 508a,
The contents of the counter 508a become larger, the value to be divided by the scaler 507 becomes larger, the frequency of the DELAY CLOCK signal becomes lower, and the delay time of the delay circuits 506a and 506b becomes larger. do. In addition, in the comparator 512b, the optimal subsequent reverberation sound reverberation time [Tsub] _p of the multiplier 520
and the subsequent reverberant sound reverberation time Tsub after being given the influence of the sound field from the encoder 511b, and if the subsequent reverberant sound reverberation time _Tsub is the optimal subsequent reverberant sound reverberation time
If Tsub is large, counter 508b
A count-up signal CU is sent out, and the contents of the counter 508b are converted to an analog value by the digital-to-analog converter 509, and then passed through the smoothing circuit 514c to the reverberation circuit 50
Attenuators 505 for each of 4a and 504b
The signals are applied to the attenuators 505a and 505b to increase the attenuation value in the attenuators 505a and 505b, thereby reducing the subsequent reverberation time Tsub. However, if the optimal subsequent reverberant sound reverberation time [Tsub] _p , the subsequent reverberant sound reverberation time Tsub
is small, a countdown signal CD is sent to the counter 508b, and the contents of the counter 508b are converted to an analog value by the digital-to-analog converter 509, and then passed through the smoothing circuit 514c to the attenuators 505a and 50.
5b, and the signal causes the attenuator 5 to
The attenuation values at 05a and 505b become smaller, and therefore the reverberation time Tsub is increased, which is the opposite operation to the above case. By the way, the amplified signals from the preamplifiers 3l and 3r before being added are input to the binaural cross-correlation coefficient calculator 519, where the binaural cross-correlation coefficient IACC is calculated and converted into analog signals. and is input to the next smoothing circuit 514b. Next, in the comparator 513b, the smoothing circuit 514
Signal from b and interaural cross-correlation coefficient IACC
is compared with a target voltage signal from variable resistor 515b which sets a target value of . If the signal from the smoothing circuit 514b, that is, the signal corresponding to the binaural cross-correlation coefficient IACC, is larger than the target signal from the variable resistor 515b,
The output signal from the comparator 513b becomes smaller and is input to the input terminal att in5 of the sound field expansion device 516.
35, the sound field expansion device 516 operates to further reduce the binaural cross-correlation coefficient IACC. However, if the signal corresponding to the binaural cross-correlation coefficient IACC is smaller than the target signal from the variable resistor 515b, the output signal from the comparator 513b becomes larger and is input to the sound field expansion device. terminal att in53
5, the sound field expansion device 516 performs an operation opposite to the above case, such as increasing the binaural cross-correlation coefficient IACC. By the way, the first reflected sound delay time analyzer 510a, which receives the addition signal added by the adder 503d, outputs a sound pressure signal φ ₀ corresponding to the audible sound pressure, and smoothes this sound pressure signal φ ₀ . After passing through the circuit 514a, the signal is input to the comparator 513a. In this comparator 513a,
Variable resistor 515a for setting the target volume value
The target voltage signal from the smoothing circuit 51
If the output signal from the smoothing circuit 514a corresponding to the listening sound pressure is larger than the target volume value from the variable resistor 515a, the output from the comparator 513a is compared with the signal from the comparator 513a. becomes larger, and the attenuator 505r, 5
The attenuation of 05l increases and the listening sound pressure is lowered. Moreover, if the signal corresponding to the listening sound pressure is smaller than the target volume value, the output from the comparator 513a becomes smaller, and the attenuators 505r and 505
The operation is opposite to the above case, as the attenuation of l becomes smaller and the listening sound pressure is increased. Furthermore, the smoothing circuit 5 shown in Fig. 14a
14a, 514b, and 514c are all used to prevent noise from occurring due to sudden signal changes, and to prevent sudden changes in the delay times of delay circuits 506a and 506b in the reverberation circuits 504a and 504b. It is used in Next, the function of the sound field expansion device 516 is
A case will be explained in which the sound field enlarging device shown in FIG. 4b is used. First, the difference component between the two signals input from the reverberation devices 504a and 504b to the input terminals inr531 and inl532 is obtained by the adder 530a, and after passing through the attenuator 536 and the low-pass filter 537, crosstalk occurs. Adders 530b,
530c from input terminal inr531 to output terminal outr533 and input terminal inl532
to the output terminal outl534. Apart from that, the output of the low-pass filter 537 is further passed through a high-pass filter 538 and given a delay or transfer rotation in a phase shift or delay circuit 539, after which the crosstalking phase is also reversed. Adders 530d and 530e add the signal to each of the above-mentioned main paths with a phase such that
33 and outl 534, respectively. By changing the attenuator 536 of this sound field expansion device 516, the interaural cross-correlation coefficient IACC
can be changed. Further, this attenuator 536 is set so that the attenuation increases as the value of the signal from the input terminal att in 535, that is, the output signal from the comparator 513b increases. Furthermore, what is shown in Figure 14c is MR.
Reverberation device 504a, 504b shown in FIG. 14a with reverberation device 504c by Schroeder and BS Atal.
If this reverberator 504c is used instead of , a more natural feeling of reverberation can be obtained. In the above embodiment, it has been described that the microphones 2r and 2l are used to obtain the sound pressure at the dummy head or at the entrance of the external auditory canal of the human head 1, but when it is not necessary to obtain the value of the interaural cross-correlation coefficient IACC, may be performed using one microphone, or even when determining the interaural correlation coefficient IACC, it may be possible to use two microphones that are not attached to a dummy head or the like. Although the acoustic signal is shown as a two-channel stereo signal, it goes without saying that there may be cases where a two-channel signal is not necessary. As described above, in the first acoustic device, the input terminals _INR , INL and the input terminals _{INR, INL ,}
Optimal first reflected sound delay time measuring means for measuring the optimal first reflected sound delay time [△t ₁ ] _p from the acoustic signal coming in from IN _L , and the optimal first reflected sound delay time [△t ₁ ] _p Optimum subsequent reverberation sound reverberation time output means that outputs an optimum subsequent reverberation sound reverberation time [Tsub] corresponding to (23±10) times _p , and a sound field signal from a microphone placed in the sound field. Audible sound pressure measuring means for measuring audible sound pressure φ ₀ , first reflected sound delay time measuring means for measuring a first reflected sound delay time Δt ₁ from the sound field signal, and subsequent reverberation sound from the sound field signal. a subsequent reverberation sound reverberation time measuring means for measuring the reverberation time Tsub; an interaural cross-correlation coefficient measuring means for measuring the interaural cross-correlation coefficient IACC from the sound field signal; and the above-mentioned optimal first reflected sound delay time. [△t ₁ ] _p and the first reflected sound delay time △t ₁ , and outputs a signal according to the difference; and the optimum subsequent reverberation sound reverberation time [Tsub] _p and Above subsequent reverberation sound reverberation time Tsub
and a second comparison means that outputs a signal according to the difference, and the delay time changes depending on the output signal of the first comparison means, and the delay time changes depending on the output signal of the second comparison means. a reverberation means for changing the reverberation time and adding reverberation sound to the acoustic signal inputted from the input terminal; and an interaural cross-correlation coefficient setting means for setting a target interaural cross-correlation coefficient value in advance. and third comparison means for comparing the binaural cross-correlation coefficient IACC with the setting value of the binaural cross-correlation coefficient setting means and outputting a signal according to the difference, and the reverberation a sound field expanding means having an output capable of receiving the output signal of the means and changing the interaural cross-correlation coefficient IACC of the sound field according to the output signal of the third comparison means; a listening sound pressure setting means that can set a value of the listening _sound pressure to be heard; 4 comparison means, attenuation means that receives the output of the sound field expansion means as input and can change the attenuation rate according to the output signal of the fourth comparison means, and amplifies the signal from the attenuation means. , an electroacoustic transducer that radiates an acoustic signal into the space, so it is not only possible to correct the sound field and create a more preferable sound field, but also to optimize the sound source within this first acoustic device. The first
The effect is that the reflected sound delay time [△t ₁ ] _p and the optimal reverberation time [Tsub] _p can be obtained, and the values of the listening sound pressure and interaural cross-correlation coefficient IACC can be changed according to the user's preference. It is something that plays. (2-2) Second acoustic device Next, sound field devices for sound fields such as Japanese-style rooms with relatively few reflections and car interiors where even if there are many reflections, the reverberation time is extremely short, Correcting the sound field based on only three physical parameters: sound pressure, first reflected sound delay time, and subsequent reverberant sound reverberation time is sufficient to create a more favorable sound field. It goes without saying that the above-mentioned first acoustic device can be used as an acoustic device in the sound field targeted here, but the sound field used is a small room like this, a Japanese-style room with relatively little reflection, or a car. When confined indoors, the second acoustic device can not only obtain the same effect as the first acoustic device without using the interaural cross-correlation coefficient IACC parameter, but also It is more compact and inexpensive, and has a simpler circuit configuration than the first acoustic device, so it is easier to work with and has better durability than the first acoustic device. It can be effective. Therefore, the sound field is corrected using three physical parameters: the audible sound pressure in the sound field, the first reflected sound delay time, and the subsequent reverberation sound reverberation time, and this second method can create a more preferable sound field.
An embodiment of the acoustic device will be described with reference to the drawings. FIG. 15 is a block diagram of an embodiment of the second acoustic device. In the figure, 451 to 453 are absolute value conversion circuits, 511d is an encoder, 551 is an input terminal _INR , 552 is an input terminal _INL , and 553 is an integral reset signal input terminal. 554 is the first reflected sound delay time analyzer, which is shown in Fig. 13a mentioned above.
Although the circuit diagram and the internal configuration of the first reflected sound delay time analyzers 510a, 510c and the subsequent reverberant sound reverberation time analyzer 510b in FIG. Attenuator 426 in the autocorrelator configuration of
It is characterized by the addition of a comparator 419. In the case of such a configuration, the above-mentioned first
It operates similarly to the reflected sound delay time analyzers 510a, 510c or the subsequent reverberation sound reverberation time analyzer 510b. Note that the same reference numerals as those in FIG. 13 and FIG. 14a indicate the same or equivalent parts. First, acoustic signals are input from the input terminals _INR 551 and _INL 552, and the two signals are added by the adder 503c and input to the first reflected sound delay time analyzer 544. This first reflected sound delay time analyzer 554 performs the same operation as the first reflected sound delay time analyzers 510a and 510c in FIG. 14a,
The output therefrom is input to the encoder 511d as in the case of FIG. 14a described above, and the optimum first reflected sound delay time [△
t ₁ ] _p is output. An encoder 511d is applied to the scaler 507 so as to obtain a delay time corresponding to this optimal first reflected sound delay time [△t ₁ ] _p .
A signal is given from The scaler 507 divides the frequency of the CLOCK signal from the input terminal 521 to create a DELAY CLOCK signal, and outputs the signal to the delay circuits 506a and 5 of the reverberation circuits 504a and 504b.
A DELAY CLOCK signal is sent to 06b.
The audio signals are input terminals IN _R 551 and IN _L 552.
are input to reverberant circuits 504a and 504b respectively, and reverberant sound is added to the attenuator 505.
r, sent to 505l. On the other hand, the signal φ ₀ corresponding to the sound pressure of the first reflected sound delay time analyzer 554 is passed through the smoothing circuit 514a to the comparator 5.
If the sound pressure is smaller than the target value, the output of the comparator 513a becomes smaller, and the output of the attenuator 513a becomes smaller. 505r and 505l are the comparators 513
It operates by reducing the amount of attenuation by the signal sent from a. However, if the sound pressure is greater than the target value,
The output of the comparator 513a increases, and the attenuators 505r and 505l increase the amount of attenuation by the signal sent from the comparator 513a, which is the opposite operation to the above case. Attenuator 505 thus obtained
The output of r, 505l is the power amplifier 517
r, 517l, speaker 518r, 5
Regenerated by 18l. At this time, the optimal subsequent reverberation sound reverberation time [Tsub] _p , which is the optimal value of the reverberation time, is (23 ± 10) times the optimal first reflected sound delay time [△t ₁ ] _p , as stated earlier. This is desirable. It is known that when a reverberator is configured as the reverberation circuits 504a and 504b, the subsequent reverberation sound reverberation time Tsub=-ε·Δt ₁ /log(g). Note that g is the attenuation rate. Here, by using the relationship Tsub=(23±10) _Δt1 , it can be seen that the attenuation rate g must be in the range of 0.588 to 0.811. In addition, when the subsequent reverberation sound reverberation time Tsub = 23△t ₁ , the attenuation rate g
=0.741. That is, the attenuation rate g
By setting the optimal first reflected sound reverberation time [△
t ₁ ] _p and the optimal subsequent reverberation sound reverberation time [Tsub] _p are obtained. Of course, even with such processing, effects in the sound field will be added, but in spaces with relatively little reflection, such as Japanese-style rooms, or spaces with a lot of reflection, such as car cabins, the reverberation time is extremely short. is very effective. By the way, in this second audio device,
The present invention aims to provide a simpler acoustic device that has the same or better effect than the first acoustic device in a small room or a sound field with relatively little reflection, such as a Japanese-style room or a car interior.
When this second acoustic device is used in a sound field other than a small room or a vehicle interior, the performance is somewhat lower than that of the first acoustic device, but it still has a high audible sound pressure, first reflected sound delay time, and subsequent reverberation. Since the sound field is corrected using three physical parameters, namely the sound reverberation time, it is possible to create a much more favorable sound field than with conventional sound devices, and the second sound device is more effective than the first sound field. It is more compact, cheaper, and has a simpler circuit configuration than other devices.
It has the advantages of good workability and good durability. As described above, in this second audio device, the input terminals IN _R and IN _L and this input terminal
Optimal first reflected sound delay time measuring means for measuring the optimal first reflected sound delay time from the acoustic signals coming in from IN _R and IN _L ; and an audible sound pressure for measuring a signal corresponding to the audible sound pressure from the acoustic signals. a corresponding signal measuring means, and receiving a signal corresponding to the optimum first reflected sound delay time as a control signal;
The above acoustic signal is input, a delay time corresponding to the above optimum first reflected sound delay time is added to the above acoustic signal, and the subsequent reverberation sound reverberation time is (23±) of the above optimum first reflected sound delay time.
10) Reverberation means set to double, audible sound pressure setting means that can set a target audible sound pressure value in advance, and audible sound pressure that is the output of the audible sound pressure corresponding signal measuring means and the audible sound pressure. a comparison means that compares the set value of the setting means and outputs a signal corresponding to the difference; and an output signal of the reverberation means is inputted, and the output signal of the reverberation means is inputted from the reverberation means in accordance with the output signal of the comparison means. Since it is equipped with attenuation means that can change the attenuation rate given to the acoustic signal and electroacoustic conversion means that amplifies the signal from the attenuation means and radiates the acoustic signal into space, the sound field can be corrected. In addition to creating a more favorable sound field, an optimal first reflected sound delay time and an optimal subsequent reverberant sound reverberation time are obtained within this second acoustic device,
This has the effect that the listening sound pressure can be changed according to the user's preference. As described above, according to the present invention, the acoustic characteristics of the sound field in which music is listened to are measured, and the physical and psychological quantities of the listening sound pressure in the sound field, the first reflected sound delay time, the subsequent reverberant sound reverberation time, and the like are measured. This has the advantage that it is possible to provide a measuring instrument for evaluating the interaural cross-correlation coefficient using four parameters.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between a reflective wall, a sound source, and a human head. Figure 2 a, b is a diagram showing an example of a normalized autocorrelation function measured using actual music. Figure 3 a, b
Figure 4 shows the results of the preference test conducted using music A and music B.
t ₁ ] _p , Figure 5 is a diagram showing the relationship between τ _p and [Tsub] _p , Figure 6 is a diagram showing the relationship between normalized preference and IACC value, and Figure 7 is a diagram showing the relationship between τ p and [Tsub] p. Figure 8 shows the relationship between the relative audible sound pressure and the preference measure _S1 , Figure 8 shows the relationship between the delay time between the direct sound and the first reflected sound and the preference measure S2, and Figure 9 shows the relationship between the delay time between the direct sound and the first reflected sound and the preference measure _S2 . The figure shows the relationship between the reverberation time of the subsequent reverberant sound and the preference scale S ₃ .
Figures 11 and 12 are diagrams showing the relationship between IACC and preference scale _S4 , and Figures 13a and 13b are block diagrams showing a schematic configuration of an embodiment of the sound field evaluation instrument according to the present invention. A diagram showing the basic configuration of a first reflected sound delay time analyzer or a subsequent reverberant sound reverberation time analyzer using a square-integral type reverberation meter, and Figures 13c and d are other configuration examples of the audible sound pressure analyzer. A diagram showing
FIG. 13e is a diagram showing an example of the configuration of a circuit for calculating the interaural cross-correlation coefficient, FIG. 14a is a configuration block diagram of an embodiment of an acoustic device to which the present invention is applied,
Figures b and c are block diagrams of the sound field expansion device and reverberator, the first
FIG. 5 is a block diagram of another embodiment of an audio device to which the present invention is applied. In the figure, 1 is a human head or dummy head, 2
r, 2l are microphones, 3, 3r, 3l are preamplifiers, 4 is a physical quantity analyzer, 5 is a comparator, 6 is a psychological quantity converter, 7 is a comprehensive evaluator, 8 is an output terminal,
9 is a recorder, 10 is a sound field evaluation measuring device, 41 is a listening sound pressure analyzer, 42, 510a, 510c, 554
5 is a first reflected sound delay time analyzer, 43, 510b is a subsequent reverberation sound reverberation time analyzer, 44 is an interaural cross-correlation function analyzer, 51 is an audible sound pressure psychological quantity converter, 5
2 is a first reflected sound delay time psychological quantity converter; 53 is a subsequent reverberation sound reverberation time psychological quantity converter; 54 is a binaural cross-correlation coefficient psychological quantity converter; 451 to 453 are absolute value conversion circuits; 501; 502,521,531,5
32, 535, 551, 552 are input terminals, 50
3a to 503d are adders, 504a, 504b are reverberation devices, 505a, 505b, 505r, 50
5l is an attenuator, 506a and 506b are delay circuits,
507 is a scaler, 508a and 508b are up-down counters, 509 is a digital-to-analog converter, 511a to 511d are encoders, 51
2a, 512b, 513a, 513b are comparators,
514a to 514c are smoothing circuits, 515a, 51
5b is a variable resistor, 516 is a sound field expansion device, 51
7r, 517l are power amplifiers, 518r, 51
8l is a speaker, 519 is an interaural cross-correlation coefficient calculator, 520 is a multiplier, and 533 and 534 are output terminals. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A microphone, an amplifier for amplifying the acoustic signal of the microphone, and an audible sound pressure measuring means for measuring the audible sound pressure from the amplified signal from the amplifier. , a first reflected sound delay time measuring means for measuring a first reflected sound delay time from the amplified signal, and a subsequent reverberant sound reverberation time measuring means for measuring a subsequent reverberant sound reverberation time from the amplified signal. , an interaural cross-correlation coefficient measuring means for measuring an interaural cross-correlation coefficient from the amplified signal, and a logarithm of 20 to the base 10 of the ratio between the audible sound pressure and the optimum audible sound pressure. When the above hearing sound pressure is greater than the optimum hearing sound pressure, the value is the 3/2 power of the insulation value, which is twice the value - (0.07±0.03)
is multiplied by -(0.04±0.02) when it is small, and outputs the value obtained by multiplying the value by -(0.04±0.02) as a measure of preference (psychological quality in terms of hearing) S1, and the first reflected sound delay time and the optimal first reflection. If the first reflected sound delay time is greater than the optimal first reflected sound delay time, set -(1.42±0.6) to the 3/2 power of the absolute value of the logarithm to the base 10 of the ratio to the sound delay time. , when it is small, a value obtained by multiplying by -(1.11±0.5) is output as the preference scale _S2 , and 10 of the ratio of the above-mentioned subsequent reverberant sound reverberation time and the optimal subsequent reverberant sound reverberation time. When the reverberation time of the subsequent reverberant sound is larger than the optimal reverberation time of the subsequent reverberant sound, the value of the absolute value of the logarithm to the power of 3/2 is -(0.74±0.25) times the sound pressure of the entire reflected sound. −(0.45
±0.15) and -(0.42±0.14) times the total sound pressure of the reflected sound when it is small, and -(2.36±
0.79), and outputs the same value as it is when the value is negative, and outputs zero when it is positive as the preference scale _S3 , and the above-mentioned interaural mutual correlation. − to the value of the 3/2 power of the number
(1.45±0.44) and outputs the value multiplied by (1.45±0.44) as the preference scale S ₄ , and comprehensively evaluates the above preference scales S ₁ , S ₂ , S ₃ , and S ₄ to obtain the overall A sound field evaluation measuring instrument characterized by comprising: a comprehensive evaluation means for outputting a scale S of . 2. The sound field evaluation measuring instrument according to claim 1, wherein the microphone is attached to a dummy head or to the entrance of the external auditory canal of a human head. 3. The optimal first reflected sound delay time and the optimal subsequent reverberant sound reverberation time are determined by the normalized autocorrelation function of the amplified signal in the first reflected sound delay time measuring means.
The sound field evaluation measuring instrument according to claim 1 or 2, characterized in that the time is set to be 0.1, and the time is set to be (23±10) times that time. 4. Claims 1 to 3, characterized in that the comprehensive evaluation means outputs the sum of the preference scales _S1 , _S2 , _S3, and _S4 as the overall preference scale S. A sound field evaluation measuring instrument as described in any of the paragraphs.