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TECHNICAL FIELD The present invention relates to a sound field correction device, and more
particularly to a device that corrects a sound field at a predetermined listening point in a sound
field produced by a direct radiation sound from a speaker and its reflection sound.
BACKGROUND ART As an example of audio equipment, there is a magnetic tape reproduction
apparatus, in which a reproduction signal from a reproduction head is amplified as a signal
having normal frequency characteristics by a reproduction amplifier having an equalizer
function, and the next stage graphic equalizer Is adjusted to a desired reproduction frequency
characteristic by a frequency characteristic variable amplifier such as, for example, to become a
speaker drive signal. In the case of the sound system, for example, the route to the
predetermined listening point 6 in the sound field shown in FIG. 2 is indicated by the direct
sound as indicated by the solid line 7 and the dotted line 8 as the sound emitted from the
speaker 5 There is a reflection with such a wall. In this case, at the listening point 6, peaks and
dips occur at frequencies that are due to mutual interference of sounds due to rain noise, and the
frequency characteristic at the listening point 6 is disturbed. Therefore, the graphic equalizer or
the like corrects the disturbance of the frequency characteristic. However, since the peak or dip
frequency changes depending on the installation state of the device or the change of the listening
position, the disturbance of the frequency also changes. Therefore, when it is intended to correct
the graphic equalizer, a large number of circuits are required and its adjustment becomes very
difficult. Therefore, the applicant of the present invention has proposed a sound field correction
apparatus as shown in FIG. In the figure, the original signal input IN is delayed at the delay unit 1
and applied to the level adjuster 2. The level-controlled signal is added via the inverter 3 as one
input 9 of the adder 4 and the original signal input IN. The addition output OUT is a drive signal
of the speaker 5 shown in FIG. In the sound field shown in FIG. 2, the reflector may be a so-called
fixed end reflection such as a wall or the like, which may generally be fixed end reflection), and
the original signal IN is Sz = ' The delay time by l is ? (lz, lx) / ? and the adjustment
level by the level adjuster 2 is KAtl / 12. In the same way, ? 1 is the path length of the direct
sound 7 of the speaker 5 up to the listening point 6 '2 is the path length of the reflected sound 8,
C is the speed of sound, A is the signal strength on the vibrating surface of the speaker, K is the
wall etc The reflectance of The output SD of the inverter 3 is SD--(KA71 / 12) e) 'Q (t-(12Zl) /') ...
(1), and thus the output So of the adder 4 Is as follows: 5o = S.quadrature.SD = A.sub.e) .omega.t
(KAh / 1z) (T (12'1) / C) (2).
This signal S is sent to the speaker 5. Is applied, so that the sound SM at the listening point 6 has
a signal strength of 1 / h and a direct sound Ss having a time delay of -t, 1 / c, and a signal
strength of 1 / h in reflectance. And it becomes synthetic sound with reflected sound SD which
has a time delay of 12 / c. Therefore, SM is the following equation. 8M = Ss + Sn ? ? (IVIs) g?
(11 / C) (KA7?12) e? (t (t2-11) / c?ll / c) + CKA7?12) gno? (t Iv'c) (K / '2) (KAt1 / lzn e)? (T(12 tl) / c-lJc) = (A /' @) e no? (T-'l / c)-(K , ?Ktl / IJ e) ? (t (272?ll) 7 c) иииииииииииииииииииииии (3) Since 0
? K <1 and 0 <ll / 72 <1, x The second term of the equation (3) is sufficiently smaller than the
first term, therefore, SM * (A / l ?) e ? (t-'h / c)-=-river = (4) The reflected wave will be
eliminated. However, a reflected wave newly generated on a wall etc. is generated in the signal
applied to the speaker to cancel the reflected wave, which is different from the second term of
the equation (3) (K / lz door 11 Ke) ? (T-(21 + lr) / c) и и и и и и и и и и (5) has the disadvantage that a
new sound is produced. SUMMARY OF THE INVENTION The present invention has been made to
eliminate the above-mentioned drawbacks, and an object thereof is to provide a sound field
correction device capable of eliminating the influence of (1) reflected sound. . According to the
sound field correction device of the present invention, when adjusting the level and phase of the
original signal and adding and superposing it to the original signal, ? ? ? is a constant with
respect to the level of the original signal. , N is a natural number, and n signals having a delay
time of n и ? (? is a constant) with respect to the original signal and having a polarity (-1 level).
To add the n signals to the original signal. EXAMPLES The present invention will be described in
detail below with reference to the drawings. FIG. 3 is a block diagram of an embodiment of the
present invention, and parts equivalent to those in FIG. 1.2 are indicated by the same reference
numerals. The original signal IN is input to n delay units 1-1-1-a and is delayed by predetermined
delay times n-.tau. Respectively. The respective delay outputs are respectively input to the nine
level adjusters 2 и 1 to 2 и 3 to receive an attenuation of ?7. Each attenuated output is input to
an inverter or buffer 3 и 1 и 3 и n, respectively. If n is an odd number, it is an inverter and the
polarity is inverted. If n is an even number, it is a buffer and does not receive polarity inversion. .
The n outputs of these inverters or buffers are added to the original signal IN by the adder 4 to 1
and become a drive signal of the speaker 5 through the power amplifier 9. Hereinafter, the
operation of the present invention will be described. As described in the operation of the
conventional example described above, if a signal with the same level but a phase difference of
18 o 0 is generated at the listening point to cancel the reflected wave, this cancellation signal is a
wall. It reflects by etc. and a new reflected wave is generated. Therefore, in the present invention,
a signal having the same level as that of the newly generated reflected wave and a phase
difference of 1800 is generated and applied to the speaker. Thus, it is possible to gradually
attenuate the reflected wave level to a level which does not cause any problem in practice by
successively canceling the reflected waves of the reflected wave cancellation signal one after
another. Specifically, as shown in FIG. 1, the signal SD represented by the equation (1) is added
and applied to the speaker. This signal SD is reflected by a wall or the like to arrive at the
listening point, and this reflected wave is represented by the second term of equation (3). In
order to cancel this reflected wave, it is better to add a signal of (11/12 second 2, AK 2) ? (2 (lz
t I> / c) ? (6) to the speaker newly. However, this (6) main signal is further reflected by a wall or
the like to be newly reflected wave at the listening point, (ll / 12) 2 и AI (?? (K / Z 2) e)? (t 1) (t
1 t2 '1' c-12 / lc)... (7) A signal is generated. ((12/12) ? ?, AI (? ? e) ? (3 (12??11) / c)... (8)
New signals can be applied to the speaker. Likewise, in order to cancel the n-th newly generated
reflected wave, (1) ? и (11 / k) ? ? Iv (K) ? ?-e no ? (n (lz?4i) / C) ииии ........ (9) comprising
signal thus may ? addition to the speaker. This is realized by the block in FIG. 3. The term (-1) in
equation (9) means that if n is an odd number, phase inversion is performed by inverter 3.n.
When n is an even number, it means that phase inversion processing is not performed by the
buffer 3. Also, the term + (KZ1 / 1z) n means passing through the level adjusters 2 и 1 ииии 2 with
an attenuation amount of ?7 as ??K 1 + / l 2. The term of the term eno ? (n (ls-1 +) / c)
means passing through a delay unit 1-1-1-z having a delay time of n и ? as ? = (4z?6tJ7).
Thus, the configuration of FIG. 3 cancels out each reflected wave and can be ignored. FIG. 4 is a
block diagram of another embodiment of the present invention, wherein n stages of circuit blocks
A and -AtL consisting of a delay unit 1, a level adjuster 2 and an inverter 3 are cascaded to form
each stage A1 to An. The respective n outputs are applied to the adder 4 to be added and
superimposed on the original signal IN. The delay units l of each stage all have delay times of ?
= Ctw?tl> / c, and the level adjusters 2 of each stage all have an attenuation amount of ??K t l
/ l 2. It is obvious that this makes it possible to almost completely cancel the reflected wave by
the same operation as the example of FIG. FIG. 5 is a block diagram showing another
embodiment of the present invention. The signal having passed through the level adjuster 2 and
the inverter 3 is fed back to the input of the delay unit 1 through the adder 10. By doing this, the
signal passes through the delay unit J having the same delay time ? and the level adjuster 2
having the same attenuation amount ? many times, so that the same effect as the example
shown in FIG. 3.4 is obtained. It will be heard. As described above, according to the present
invention, a plurality of reflected wave cancellation signals are generated and added to the
original signal, so that the effect of the reflected waves can be substantially ignored. is there.
Brief description of the drawings
FIG. 1 is a block diagram of a sound field correction apparatus proposed by the applicant of the
present invention, FIG. 2 is a view showing an example of a sound field, and FIGS. 3 to 5 are
embodiments of the present invention. It is a block diagram showing each.
Explanation of the symbols of the main part 1 иии Delay 2 иии Level adjuster 3 иии Inverter 4 иии Adder
5 иии Speaker applicant Pioneer Corporation Attorney Attorney Fujimura Motohiko 3I27
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