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JP2003153398

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2003153398
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
apparatus and method for sound image localization in the front-rear direction by headphones
which faithfully reproduces and localizes a sound image in the front-rear direction in a simple
manner in headphones.
[0002]
2. Description of the Related Art When listening to a sound source such as a CD using
headphones, the sound image is generally localized in the head, not in front, and is said to be
localization in the head.
[0003]
On the other hand, there is also a device that tries to reproduce the sound with headphones as if
the sound comes out from the front and back direction as it is in a movie theater as if it is a
surround effect, and it is said to be a virtual sound.
[0004]
As a device for reproducing the sound from the front and rear direction with a headphone, one
using a head-related transfer function (also called HRTF (abbreviation of Head-Related Transfer
Function)) is often used.
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For example, in surround headphones recommended by Dolby, 5 channels of sound source
signals corresponding to the arrangement of sound sources are reproduced by the headphones,
so 3 channels in the forward direction (L, C, R) and 2 channels in the rear direction (SL, SR) The
respective sound source signals are input to the headphones through a head related transfer
function corresponding to the sound source direction.
In this case, there is a limit to the reproduction of the sense of reality, and it is difficult to express
the arrival of sound from the front and back direction with headphones.
[0005]
Therefore, it has become clear, for example, in Spacial Hearing (Brawelt) that the peak of the
monophone spectrum seems to be one of the cues in judgment of the front and back sense. For
example, JP-A-10-136497 and JP-A-9- No. 233600 also attempts to give a sense of front and
back by increasing or decreasing a specific frequency.
[0006]
However, since these are not considered at all to reproduce other than a specific frequency, and
do not use the head transfer function of the listener, the head transfer function when the sound
comes from the front and back direction is faithfully reproduced It can not be said that it is not
something that expresses the sense of context for each listener.
[0007]
Therefore, there have been attempts to measure the head transfer function of the listener and
reproduce it to localize the sound source forward or backward.
However, in order to measure the listener's own head transfer function, a small and highperformance microphone must be attached to the listener's ear canal, and the degree of sealing
of the ear canal affects the measurement accuracy, which is difficult. There are many things.
Also, the head related transfer function of one listener can not be applied to other listeners, and
each time the listener changes, the head related transfer function has to be re-measured each
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time, which is time-consuming and unrealistic. When used by listeners, there are many
inconveniences such as having to measure and store data each time.
[0008]
SUMMARY OF THE INVENTION The present invention has been made to solve such conventional
problems, and it is a simple method to faithfully reproduce and localize a sound image in the
front and back direction, and to reproduce in the front and back direction by headphones A
sound image localization apparatus and method are provided.
[0009]
A sound image localization apparatus according to the present invention in the back and forth
direction with headphones comprises a filter that simulates a predetermined adjustable headrelated transfer function corresponding to the front and back direction, and headphones through
the filter It was decided to input sound source signals and to localize sound images before and
after.
[0010]
Further, the sound image localization apparatus according to the present invention in the back
and forth direction of the headphone comprises: a diffuse filter simulating a monophone
spectrum in a diffuse sound field; and a center frequency predetermined in an audible band and a
half width of the center frequency. A front / rear filter connected in series to the filter is provided
to reproduce a head-related transfer function specific to the listener and to localize the sound
image before and after.
[0011]
The front / rear filter has a predetermined peak of 4 kHz for localization of the sound image in
the forward direction and a predetermined peak of 8 kHz for localization of the sound image in
the backward direction. The dips are adjusted so as to generate dips at 10 kHz and
predetermined ones at 10 kHz, and the head transfer function specific to the listener is
reproduced by adjusting the center frequency and the half width of the center frequency. .
[0012]
Further, in the sound image localization method in the back and forth direction by the
headphones of the present invention, a sound source signal is input to the headphones through a
filter imitating a predetermined adjustable head transfer function corresponding to the front and
back direction to localize sound images before and after. And
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[0013]
Further, the sound image localization method in the back and forth direction by the headphone
according to the present invention comprises: a diffuse filter simulating a single ear spectrum in
a diffuse sound field; and a center frequency predetermined in an audible band and a half width
of the center frequency. The front and rear filters are connected in series to reproduce the headrelated transfer function specific to the listener and to localize the sound image before and after.
[0014]
Furthermore, when the sound image is localized in the forward direction, the peak at a
predetermined proximity of 4 kHz and the dip at a predetermined proximity of 8 kHz, and when
the localization in the backward direction is a dip at 10 kHz The front / rear filter is adjusted to
produce a dip at a predetermined vicinity, and the head-related transfer function unique to the
listener is reproduced by adjusting the half-width of the center frequency.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the drawings.
[0016]
FIG. 1 shows a block diagram of a sound image localization apparatus 10 according to the
present invention in the front-rear direction with headphones.
[0017]
As shown in FIG. 1, the sound image localization apparatus 10 in the front-rear direction by
headphones inputs a diffuse filter 11 for inputting a mono or stereo sound source signal 13 and
an output signal 14 from the diffuse filter 11 to headphone 15. It has a front / rear filter 12 to
output.
[0018]
The mono or stereo source signal 13 input to the diffuse filter 11 simulates the monophone
spectrum in the diffuse sound field, which is an average value of the head transfer function
spectrum corresponding to all directions.
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[0019]
FIG. 2 shows a measurement diagram when measuring a monophone spectrum.
[0020]
As shown in FIG. 2, the monophone spectrum can be obtained by arranging the sound source at
every 5 ° in the horizontal plane with respect to the dummy head 20 (for example, the KEMAR
dummy head manufactured by Knowles Electronics Company) and measuring | Hn (f) | .
│H n (f) │ is the head transfer function of the left ear in the direction of the n-th sound source
when a plurality of sound sources No. 1, No. 2, No. n... It is an absolute value.
[0021]
FIG. 3 shows the frequency characteristics of the diffuse filter 11.
By passing the diffuse filter 11, the sound source signal 13 can be given a sense of presence.
[0022]
FIG. 4 shows a relative monophone spectrum when sound comes from the front and back
direction with reference to the monophone spectrum in the diffuse sound field.
[0023]
As shown in FIG. 4, the monophone spectrum 12F when the sound source is in front has a peak
at about 4 kHz and a dip at about 8 kHz as compared to the diffuse sound field.
In the case of the monophone spectrum 12R in the rear, there is a dip at about 4 kHz and a dip at
about 10 kHz.
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[0024]
FIG. 5 shows the frequency characteristics of the front / rear filter 12.
[0025]
As shown in FIG. 5, the front / rear filter 12 inputs the output signal 14 from the diffuse filter 11
simulating the monophone spectrum in the diffuse sound field, and makes the center frequency
and half width of the peak or dip variable. .
In the case of localization at the front, a peak FP1 at about 4 kHz and a dip FD1 at about 8 kHz,
and in the case of localization at the rear, a dip RD1 at about 4 kHz and a dip RD2 at about 10
kHz.
However, since the optimum values of the center frequency and the half width of the peak and
dip are different depending on the listener, the center frequency and the half width are adjusted
so that each listener can feel the front and back feeling most.
[0026]
As described above, the sound image localization apparatus 10 according to the present
invention in the front to back direction can faithfully reproduce the sound image in the front to
back direction with respect to each listener without taking the trouble of measuring the head
transfer function of the listener. By giving time difference and level difference to the signal, the
sound image can be easily reproduced in any direction of the horizontal plane.
[0027]
In the above embodiment, although the sound image localization apparatus in the front-rear
direction by the headphones has been described, the diffuse filter 11 and the front / rear filter
12 are function procedures and the sound image localization method in the front-rear direction
by the headphones be able to.
[0028]
According to the present invention, the sound image localization apparatus in the front and back
direction by the headphone according to the present invention comprises a filter imitating a
predetermined adjustable head transfer function corresponding to the front and back direction,
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and the sound source signal is input to the headphone through the filter. Since the sound image
is localized before and after, it is possible to faithfully reproduce and localize the sound image in
the front and back direction by a simple method using headphones.
[0029]
Further, the sound image localization apparatus according to the present invention in the back
and forth direction of the headphone comprises: a diffuse filter simulating a monophone
spectrum in a diffuse sound field; and a center frequency predetermined in an audible band and a
half width of the center frequency. Since the front / rear filter connected in series to the above
filter is provided to reproduce the head-related transfer function peculiar to the listener and the
sound image is localized before and after, in the front and back direction by a simple method to
obtain realism in headphones The sound image can be faithfully reproduced and localized.
[0030]
The front / rear filter has a predetermined peak of 4 kHz for localization of the sound image in
the forward direction and a predetermined peak of 8 kHz for localization of the sound image in
the backward direction. The dips are adjusted to create a dip at around 10 kHz and a
predetermined dip at 10 kHz, and the head transfer function specific to the listener is reproduced
by adjusting the center frequency and the half-width of the center frequency. The sound image in
the front-rear direction can be reliably reproduced and localized for each listener without the
trouble of measuring the head related transfer function of the listener.
[0031]
Further, in the sound image localization method in the back and forth direction by the
headphones of the present invention, a sound source signal is input to the headphones through a
filter imitating a predetermined adjustable head transfer function corresponding to the front and
back direction to localize sound images before and after. Therefore, the sound image can be
faithfully reproduced and localized in the front-rear direction by a simple method in the
headphones.
[0032]
Further, the sound image localization method in the back and forth direction by the headphone
according to the present invention comprises: a diffuse filter simulating a single ear spectrum in
a diffuse sound field; and a center frequency predetermined in an audible band and a half width
of the center frequency. The front and rear filters are connected in series to reproduce the headrelated transfer function unique to the listener and to localize the sound image before and after,
so the realism in the headphones is obtained and the sound image is faithful in the front and
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back direction by a simple method Can be reproduced and localized.
[0033]
Furthermore, when the sound image is localized in the forward direction, the peak at a
predetermined proximity of 4 kHz and the dip at a predetermined proximity of 8 kHz, and when
the localization in the backward direction is a dip at 10 kHz The front / rear filter is adjusted so
as to create a dip at a predetermined vicinity, and the head transfer function unique to the
listener is reproduced by adjusting the half width of the center frequency. The sound image in
the front-rear direction can be reliably reproduced and localized for each listener without the
trouble of measuring the partial transfer function.
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