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JPS55112098

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DESCRIPTION JPS55112098
Description 1, title of the invention
Headphone signal reproduction device
3. Detailed Description of the Invention When the present invention reproduces and listens a
stereo or monophonic sound reproduction signal with a headphone, the stereo or monophonic
sound so as to obtain a sound image similar to that upon reproduction and listening by the
speaker 7 stem. In general, the sound reproduction signal source is reproduced by the speaker
system, except for special signals such as a sound pickup signal by a dummy head microphone
related to a signal correction device for headphones which performs appropriate electric signal
processing (II) in advance to an original signal for reproduction It is created assuming that it will
be heard. Therefore, the signal source for sound reproduction generally used at present is not
suitable for reproduction and listening by headphones. In fact, when a general sound
reproduction signal is directly reproduced by headphones, only a very unnatural sound image
localization feeling that a sound image is generated in or near the head can be obtained. Under
the circumstances, there has been proposed a method of adding various electrical signal
processing to stereo or mono-2 sound reproduction signals on the assumption that sound
reproduction signals from a speaker system are previously assumed in order to avoid such aural
phenomenon. However, conventional electrical signal processing does not necessarily achieve
sufficient effects, and (b) the sense of psychological distance from the head to the sound image is
small, and (b) the sound image is unnatural, and it is spread and clear There was a drawback
such as lack of speed. (2) EndPage: 1 Therefore, the present invention is regarded as the above,
and the above-mentioned drawbacks in the reproduced sound image are eliminated to provide a
sharp and clear sound image localization effect with a large sense of psychological distance from
the listener to the sound image. It is an object of the present invention to provide a headphone
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signal correction apparatus that can be obtained. The present invention will be described below.
As described above, when the speaker reproduction signal is directly reproduced and listens to
the headphone, the sense of localization in the head of the sound image is generated, while when
the sound pickup signal by the dummy head microphone is similarly reproduced and listened to
the headphone, the sound image is out of the head Localize to From this, the effect of localization
outside the head of the sound image is considered as a unique phenomenon during dummy head
microphone sound collection / reproduction, but in actuality these effects are reproduced by
headphones rather than the intervention of the dummy head microphone itself. Depending on
the presence or absence of the reflected sound component in the signal sound, the addition of
the reflected sound component -1 by an appropriate method regardless of the dummy head
microphone sound collection gives a sense of localization outside the head of the sound image. 1
и и I binaural signal to a ready-made sound reproduction signal system synthesis 4 и = 12. (3)
However, simply combining and adding the ? reflection component is insufficient as in the
conventional example, the sense of localization is incomplete, the sense of distance of the sound
image is small, and the unnatural spread It will be accompanied by a feeling. This is because the
artificially synthesized reflected sound signal has a different structure compared with that in the
real sound field.
That is, in order to obtain an auditory sense of natural localization outside the head, it is
necessary that the characteristics of the artificial binaural signal including the reflected sound
component be similar to that of the real sound field. Therefore, in order to determine the
characteristic condition of the pinaural signal that gives the desired psychological effect, that is, a
sharp and sound image effect with a sufficient sense of distance, the following sensory
experiment was tried. That is, the monaural signal output obtained by branching the monaural
signal into two systems and supplying the two systems of signals to the electric signal processing
circuit was reproduced and listened to by headphones, and an evaluation experiment regarding
sound image localization was performed. As the characteristics of the above-mentioned pinaural
signal, three kinds of physical quantity parameters which macroscopically reflect the reflected
sound structure (4), ie, (i) direct sound energy density ratio of reflected sound, (ii) remaining time
corresponding to reverberation envelope (C) By focusing on the degree of correlation of the
acoustic signal between both ears, these three types of physical quantities were variously
changed to evaluate the sense of the distance outside the head of the sound image and the sense
of the spread of the sound image. As a result, the correspondence between the sense of distance
and the sense of spread of the sound image and the physical quantity representing the
macroscopic structure of the pinaural signal including the reflected sound became clear. It is
shown below. (I) When the time function of the pinaural signal is exactly the same between
listeners' ears, ie, when the binaural signal correlation degree is 1, the head of the sound image
regardless of the magnitude of the reflected sound energy and the length of the reverberation
time It is hard to produce a sense of external orientation. (11) When the degree of correlation of
the binaural signals is not 1, the sense of localization of the sound image outside the head tends
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to increase as the reflected sound density is higher and as the remaining time is longer. In this
case, there is not much change in the sense of spreading of the sound image. Further, if the
physical pressure difference function 5 o (j?) and the interaural sound pressure crosscorrelation coefficient 0 0 are considered as (5) physical quantities representing the correlation
of sound pressure signals between both ears, there are the following conditions. Here, sound
pressure impulse responses in the left and right ear canal population are 1 (t) and R (t), and their
Fourier transform pairs are L (j?) and R (j?). That is, L (j?) = F (l (t)) and R (j?) = F (R (t)). The
binaural sound pressure difference function is fixed at 5o (j?) L (j?) // R (j?), and the
interaural sound pressure cross-correlation coefficient 0 0 is defined by iL. (Iii) In the case of the
binaural sound pressure difference function S (j?) 41 and ll5 (j?) 1-1, the sense of distance of
the sound image is large and the convergence of the sound image is high as compared with the
case where this condition is not satisfied. . (1v) The sense of distance of the sound image tends to
increase as the average value of the inter-ear sound pressure cross-correlation coefficient 0 0 in
the audio frequency band decreases.
(6) EndPage: inter-ear sound pressure cross-correlation coefficient ? measured with 2 ? (V)
band noise and signal source-C. The sound image becomes sharper and clearer as the pattern of
the frequency characteristic of the sound quality becomes similar to that in the real sound field.
Note that the interaural sound pressure cross correlation coefficient ? measured at the binaural
position in a real sound field. A typical example of the frequency characteristic of is as shown in
FIG. As clearly shown in FIG. 1, the both-ear pressure cross correlation coefficient ? at the
arrival site. The higher the frequency f, the interaural sound pressure cross-correlation
coefficient ?. The value of, is low, showing a monotonically decreasing pattern. Based on the
above experimental results, experiments were performed to synthesize pinaural signals using a
specific sound field as a model. The reflected sound to direct sound energy ratio and
reverberation time are set to the same values as the model sound field, and for the interaural
sound pressure correlation degree, the absolute value of the interaural sound pressure difference
function 5o (j?) is 1, A correction was made to make the pattern of the frequency characteristics
of the interaural sound pressure cross-correlation coefficient 0 0 similar to the model sound field.
As a result, regarding the listening window at the time of reproduction, both the sense of distance
and the sense of expansion of the sound image are highly similar to the listening window in the
model sound field, and the localization feeling of the natural sound image is realized. By setting
the three physical quantities described above to the optimum value 11 at the time of correction,
it is possible to realize a sound image localization feeling having a sharp and sufficient sense of
distance and a sense of expansion at the time of sound material reproduction. FIG. 2 is a block
diagram of an embodiment of the present invention 3. Signal correction device for headphones
[17 is composed of right and left channel signal correction circuits 17-1 and 17-2 and right
channel signal correction circuit 17-1. Is a subtractor 2 for subtracting the output of the
attenuator 1 having the gain g from the speaker reproduction signal RIN on the right channel,
and a delay circuit having an output of the subtractor 2 as an input and a delay time ?t, that is, a
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transfer function e-Jo) Jt 3 and an integrator 4 having a transfer function 1 / (1 + J?T +) with
the output of the delay circuit 3 as an input, an amplifier 5 which doubles the output of the
integrator 4, and the output of the delay circuit 3 from the output of the amplifier 5 An adder 8
for adding the output of the subtracter 6 and the output of the attenuator 7 of the gain g for
attenuating the speaker reproduction signal RIN of the right channel; The output is output to the
attenuator 1 and configured so as to be an output signal RO to the signal); The integrator 4 has,
for example, a resistor and a capacitor, and its time constant is TI. Further, the gains g of the
attenuators 1 and 7 are configured to change in conjunction with each other.
Similarly, the left channel signal correction circuit 17-2 also has attenuators 9 and 15 of gain g,
subtractors 10 and 14 and a delay circuit 11 having a delay time ?t, ie, a transmission amount
ye-j??Jt, and a time constant It consists of an integrator 12 of T2, an amplifier 13 with an
amplification factor of 2, and an adder 16 and subtracts the speaker reproduction signal LIN of
the left channel and inputs it to the unit 10 and outputs the output of the adder 16 to
headphones Configure to be the signal LO. The integrator 4, the amplifier 5 and the subtracter 6
constitute a phase circuit A, and the integrator 12, the amplifier 13 and the subtractor 14
constitute a phase circuit B. The headphone signal correction unit (9) configured as described
above delays the signals RIN and LIN by the delay circuit 3.11 to the input signals RIN and LIN as
direct sound, respectively, to reduce the size of the narrowing unit 1.7.9. , And the reflected
sound component obtained by changing the phase by the phase circuits A and H is added. First,
the amplitude transfer rates R (0) of the right and left channel signal correction paths 17-1 and
17-2 shown in FIG. 2 and L (?) are -1. ... (1). Similarly, L (?) becomes L (?) -1... (2). That is, the
amplitude transfer rates P (?) and L (?) of the right and left channel signal correction circuits
17-1 and 17-2 are angular frequency ?, gain of attenuator ? delay time ?t of delay circuit,
integration Time constant T1. , T2 (10) EndPage: 3 regardless of-foot. Also, the ratio S (?) of the
amplitude transfer ratio of the right and left channel signal correction circuits 17-1 and 17-2 is S
(?) -R (?) / L (?) -1. ... (3). Further, the energy density ratios ER, / D of the reflected sound
signal to the direct sound signal are the left and right channels. The reverberation time TB% TL
for each of the left and right channels is the reverberation time TR for the right channel. The
reverberation time TL for the left channel is also the above equation (5) g-Note that TI-in the case
of T2 << ?t, R-TL is there. Next, when the same narrow band noise is input to the left and right
channel signal correction circuits 17-1 and 17-2, the cross correlation coefficient between the
output signals of both channel and channel signal correction circuits 17-1. And 17-2. As for ?, if
the center frequency fo of the band noise is generally shown on the horizontal axis, it has
frequency characteristics as shown in FIG. 3, and the change of the crossmantissa condylar
region where the cross correlation coefficient ? ? is an integral in the phase circuit The slope
depending on the values of the time constants T1 and T2 of the unit is determined depending on
the value of the difference between the time constants TI and T2, and the coefficient value is
determined by the gain g of the attenuator.
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Now, for each circuit constant of the headphone signal correction device IJ, delay time ?j-15 ms,
time constant TI = 100 ?s, time constant T2 sufficiently small, and a value close to almost zero,
attenuator gain g = = The frequency characteristic of the cross correlation coefficient ? when it
is set to 0.7 is as shown in FIG. 4. As is clear from FIG. 4, the cross correlation coefficient ? is
from 1 to about 1 as the frequency f increases. It decreases monotonically at 031. As described
above, the headphone signal correction device 17 shown in FIG. 2 has the amplitude transfer of
the left and right channel signal correction circuits regardless of the time constants T1 and T2 of
the integrator, the gay 7g of the attenuator, and the delay time .DELTA.t of the delay circuit. The
ratio R (?), L (?) and the ratio S (?) of the amplitude transfer ratio are constant regardless of
the frequency, and by setting the time constants T1 and T2, the gain g and the delay time ?t
Energy density for direct sound signal. The ratio EMD% The reverberation time TL% '14 ? of
each left and right channel should be set by a member, and the desired characteristic condition
should be satisfied also for the listener's binaural sound pressure signal correlation. it can. The
absolute value S (?) of the ratio of the amplitude transfer ratio of the left and right channel
signal correction circuits 17-1 and 17-2 is a binaural sound pressure difference function S. In
(j?), the cross-correlation coefficient ? corresponds to the binaural sound pressure crosscorrelation coefficient 0 0 respectively, S (?) is 1 as in 5O (j?), and FIGS. 4 and 1 As apparent
from the comparison with the figure, both decrease monotonously as the frequency increases.
(13) Therefore, by setting the delay time ?t of delay circuits 3 and 11, time constants T1 and T2
of integrators 4 and 12, and gain g of attenuators 1.7.9 and 15, desired left side Signal correction
device for headphones adjusted to the characteristic conditions of energy density ratio ER, / D for
direct sound signal of reflected sound signal of channel, reverberation time TR and TL of each
left and right channel, and binaural sound pressure signal correlation degree of listener The
signal from the signal source 18 is corrected with the input 17 as shown in FIG. 5 by using the
reference numeral 17 and then amplified by the amplifier 19 and heard by the headphone 21 to
obtain a sharp and sufficient sense of distance. A natural sound image localization is realized. In
addition, 20 has shown the listener. Also, in this case, there is no change in the spectrum of the
sound, which is apt to occur at the time of reflection sound addition, so-called coloration. As
described above, according to the present invention, the disadvantages of the conventional
headphone signal correction apparatus can be eliminated, and a sense of distance from a listener
to a sound image can be obtained, and a sharp and clear sound image localization effect can be
obtained.
(14) EndPage: 4 heat theory, it is most desirable to simulate the reflected sound structure in a
real sound field over a fine area and reflect it on a pinaural signal, but an infinite number of
reflections that differ in level, spectrum, arrival time and arrival direction etc. It is extremely
difficult in reality to simulate sounds exactly. The present invention does not necessarily perform
exact simulation, and based on the correspondence between the physical quantity obtained
macroscopically capturing the reflected sound structure and the psychological quantity caused
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thereby, the psychological effect to be finally obtained is obtained. There is an advantage that the
configuration of the correction circuit becomes simple because it is obtained.
4. Brief description of the drawings Fig. 1 shows the frequency characteristics of the interaural
sound pressure cross correlation coefficient in a real sound field. FIG. 2 is a block diagram of an
embodiment of the present invention. FIG. 3 shows the frequency characteristic C of the cross
correlation coefficient between output signals at the time of band noise input according to an
embodiment of the present invention FIG. 4 shows appropriate values for each constant of the
headphone signal correction apparatus according to an embodiment of the present invention
Frequency characteristics of mutual (15) correlation coefficient when set to. FIG. 5 is a block
diagram showing an example of using one embodiment of the present invention. 1.7.9 and 15 иииии
Attenuator, 2.6.10 and 14 иииииииииииииииииии 3 and 11 ииииии Delay circuit, 4 and 12 ииииииии Integrator , 5 and
13... Amplifiers, 8 and 16... Adders 17-1 and 17-2... Right and left channel signal correction
circuits. Patent Applicant Trio Co., Ltd. (16) Fig. 1 U7-2 Fig. 3 ? j Fig. 5 EndPage: ?
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