JP6511999B2 - Out-of-head localization filter generation device, out-of-head localization filter generation method, out-of-head localization processing device, and out-of-head localization processing method - Google Patents

Description

  The present invention relates to an extra-head localization filter generation device, an extra-head localization filter generation method, an extra-head localization processing device, and an extra-head localization processing method.

  Patent Literatures 1 and 2 describe an out-of-head localization method in headphones and earphones. In Patent Documents 1 and 2, a dummy head is used to obtain a transfer function from the entrance of the ear canal to the tympanic membrane. The inverse function of the transfer function from the entrance of the ear canal to the tympanic membrane is called the ear canal correction function.

  In addition, Non-Patent Document 1 uses an binaural signal as a sound source and uses headphones such that the ratio of acoustic impedance is 1, so that the ear canal correction function is determined by the sensitivity of the microphone and the sound pressure at the entrance of the ear canal. It is stated that it is easily required. The binaural sound source is a sound source on which the head transfer function of the recording person is reflected.

  The ear canal correction function obtained in this manner is a part of a plurality of filters constituting the out-of-head localization filter. Hereinafter, the plurality of filters constituting the out-of-head localization filter, including the ear canal correction function, will be hereinafter referred to as the out-of-head localization filter for the sake of convenience.

JP 2004-128854 A JP 2002-209300 A

Henrik Moller "Fundamentals of Binaural Technology" Applied Acoustics 36 (1992)

  Non-Patent Document 1 discloses a method of obtaining an acoustic transfer circuit (transfer function) by headphone reproduction equivalent to an acoustic transfer circuit (transfer function) from a sound source in a free sound field to an eardrum.

  In Non-Patent Document 1, using a binaural signal recorded with the ear canal entrance closed as a sound source, the subject at the time of recording and the subject at the time of listening (listener) are the same, and 'open headphone' described later By using it, it is described that an out-of-head localization filter can be easily obtained. The 'open headphone' is a headphone in which the ratio of each acoustic impedance shown in the following equation (1) is 1.

In addition, the symbol used for Formula (1) is as follows.
P ₂ : Sound pressure of dummy head or listener's closed ear canal entrance position in free sound field P ₃ : Sound pressure of dummy head or listener's open ear canal entrance position in free sound field P ₅ : Headphones Sound pressure P ₆ of the closed ear canal entrance position of the listener at the time of listening: Sound pressure Z _{ear canal} of open _{ear canal} entrance position of the listener at the time of headphone listening: acoustic impedance seen from the _{ear canal} entrance Z _headphone : Acoustic impedance seen from the entrance of the ear canal at the time of headphone listening Z _radiation : Acoustic impedance seen from the entrance of the ear canal at the free sound field where P ₃ is a first sound pressure, P ₂ is a second sound pressure, the _{P 6} a third sound pressure is _{P 5} is a fourth sound pressure.

Then, according to Non-Patent Document 1, when the subject at the time of recording and the subject at the time of listening (listener) are the same and the headphone or the earphone satisfies the condition of 'open headphone', the microphone sensitivity M ₁ and the headphone terminal voltage It is disclosed that if the E _headphone and the sound pressure P ₅ are obtained, the out-of-head localization filter G _c can be calculated as the approximate value G _c ^* by the following equation (2).

In addition, the symbol used for Formula (2) is as follows.
G _c : Out-of-head localization filter G _c ^* for equalizing the free sound field and headphone listening when using the sound pressure P ₂ of the dummy head or the closed ear canal entrance position of the listener in the free sound field : An approximate value of G _c , and the external localization filter M ₁ when using 'open headphone' M ₁ : Microphone transfer function P ₅ at the time of recording: sound of the blocked position of the ear canal at the listener when listening to headphones Pressure E _headphone : Headphone terminal voltage

12, the sound pressure P ₃ and the sound pressure P ₄ is a diagram schematically showing. The sound pressure P ₄ is in a free sound field, a sound pressure of the eardrum position of the dummy head or the listener. Figure 13 is a diagram schematically showing a sound pressure P ₆ and the sound pressure P _7. The sound pressure P ₇ is at a headphone listening, a sound pressure of the eardrum of the listener. Although P ₂ and P ₅ of the formula (1) is shown only in the circuit diagram of FIG. 12 and FIG. 13, in the same position as P ₃ and P _6, respectively, closing the ear canal entrance in earplug (earplugs), etc. Sound pressure in the state.

  However, Non-Patent Document 1 does not touch on an earphone. Since the acoustic impedance of the earphone and the acoustic impedance of the free sound field are largely different, making the ratio of Equation (1) 1, that is, satisfying the condition of 'open headphone' is structurally difficult to realize.

  The present invention has been made in view of the above points, and an out-of-head localization filter generating device for generating an out-of-head localization filter capable of appropriately localizing a sound image out of the head even when using an earphone, an out-of-head localization filter generation Abstract: A method, an out-of-head localization processing apparatus, and an out-of-head localization processing method are provided.

  An out-of-head localization filter generating device according to one aspect of the present invention includes a measuring pipe having a straight pipe portion, a microphone provided in the straight pipe portion in the measuring pipe, and an earplug for fixing the microphone to the measuring pipe. An earphone attached to the measurement pipe, a speaker installed outside the measurement pipe, and a first sound pressure, a second sound pressure, a third sound pressure, and a fourth sound pressure A processing unit for generating an out-of-head localization filter, wherein the microphone is installed without being fixed to the measurement pipe by the earplug, and freedom is achieved when the speaker is driven without attaching the earphone to the measurement pipe The sound pressure of the sound field was measured by the microphone to be the first sound pressure, the microphone was fixed to the measurement pipe with the earplug, and the speaker was driven without attaching the earphone to the measurement pipe The microphone measures the sound pressure of the free sound field And the microphone is installed without being fixed to the measurement pipe by the ear plug, and the microphone measures the sound pressure when the earphone is driven, and the third sound is generated. The microphone is fixed to the measurement tube by the ear plug, and the microphone measures the sound pressure when the earphone is driven, to obtain the fourth sound pressure.

  An out-of-head localization filter generating method according to an aspect of the present invention includes a first sound pressure, a second sound pressure, a third sound pressure, and a fourth using a measuring tube, a microphone, an earplug, an earphone, and a speaker. Measuring the sound pressure of the second sound pressure, generating the external localization filter based on the first sound pressure, the second sound pressure, the third sound pressure, and the fourth sound pressure; The measurement tube has a straight tube portion, the microphone is provided on the straight tube portion in the measurement tube, the ear plug and the microphone are fixed to the measurement tube, and the earphone is The speaker is mounted on a measuring tube, the speaker is installed outside the measuring tube, the microphone is installed without being fixed to the measuring tube by the earplug, and the earphone is not installed on the measuring tube. The sound pressure of the free sound field when Measuring the first sound pressure, fixing the microphone to the measurement pipe with the earplug, and sound pressure of a free sound field when the speaker is driven without attaching the earphone to the measurement pipe The microphone measures and sets the second sound pressure, the microphone is installed without being fixed to the measurement tube by the earplug, and the microphone measures the sound pressure when the earphone is driven, The third sound pressure is used, the microphone is fixed to the measurement tube with the earplug, and the sound pressure when the earphone is driven is measured by the microphone to be the fourth sound pressure.

  According to the present invention, an out-of-head localization filter generating device for generating an out-of-head localization filter capable of appropriately localizing a sound image outside the head even when using an earphone, an out-of-head localization filter generating method, an out-of-head localization processing device And an out-of-head localization processing method can be provided.

It is a figure explaining the view of an out-of-head localization filter. It is a figure explaining the view of an out-of-head localization filter. It is a figure explaining the view of an out-of-head localization filter. It is a figure explaining the view of an out-of-head localization filter. It is a figure for demonstrating the measurement for producing | generating an out-of-head localization filter. It is a figure for demonstrating the measurement for producing | generating an out-of-head localization filter. It is a figure for demonstrating the measurement for producing | generating an out-of-head localization filter. It is a figure for demonstrating the measurement for producing | generating an out-of-head localization filter. It is a block diagram which shows the structure of an out-of-head localization processing apparatus. It is a schematic diagram which shows a mode that the individual characteristic adjustment in the out-of-head localization process is performed. It is a flowchart for demonstrating the operation | movement of the personal characteristic adjustment in the out-of-head localization process. In free sound field, the sound pressure P ₃ of the opened ear canal entrance position of the dummy head or the listener, in a free sound field, is a diagram schematically showing a sound pressure P ₄ of the eardrum position of the dummy head or the listener . During headphone listening, a sound pressure P ₆ in the opened ear canal entrance point of the listener, there during headphone listening, a sound pressure P ₇ of the eardrum of the listener a diagram schematically illustrating

Embodiment 1
[Summary of the Invention]
In the out-of-head localization processing up to now, the position of the virtual sound source heard from the earphone is localized in front of (the position closer to the listener) than the position of the actual sound source although it appears outside the head. In addition, the sound quality often changes (sound with a certain frequency is emphasized). There are the following two reasons as these causes.

  The first reason is that the characteristics of the ear canal substituted by the dummy head do not exactly match the characteristics of the user. Human sound localization can be treated as a one-dimensional problem from the entrance of the ear canal to the tympanic membrane. However, strictly speaking, the ear canal is S-shaped, and the way it is bent differs depending on the individual. The length of the ear canal is said to be 25 to 30 mm, and the resonance frequency varies depending on the length.

  The second reason is that the wearing state of the earphone may not be appropriate. When the wearing condition of the earphones was observed in an experiment with about 300 subjects, the large earpiece was forcibly pushed and naturally detached or obliquely inserted, and the sound path was blocked by the wall of the ear canal. There were many subjects who did not wear the earphone properly.

  In the first embodiment, proper out-of-head localization can be performed by dividing into (A) characteristics common to all persons and (B) individual-specific characteristics shown below and adjusting only (B) to each individual. To realize.

(A) Characteristics Common to All People The sound pressure for determining the localization filter outside the head is measured using a structure that models the ear canal, that is, a measurement tube whose one end is closed. For example, the sound pressure is measured by installing a microphone at a position 0.5 to 1 cm from the tip of the earpiece in a state in which the entire earpiece is closely fitted along the ear canal. Through measurement, we obtain universal out-of-head localization filters that are not individualized.

(B) Individual-Specific Characteristics The universal out-of-head localization filter acquired above is assumed to cause the one-dimensional vibration of a tube called the ear canal. Therefore, the occurrence of the resonance occurring in the ear canal blocked by the tympanic membrane is not considered. The resonance causes only certain high frequencies to be heard louder, or conversely no sound at all. The frequency at which such resonance occurs is an individual characteristic, and the occurrence of resonance is inevitable. In addition, when the wearing state of the earphone is not appropriate, it also relates to the characteristics of each individual. Since such individual characteristics can be perceived only by the listener, adjustment by the listener specifies the resonance frequency. A mechanism is provided to perform the attenuation or enhancement process using a notch filter or peaking filter to eliminate resonances caused by the modeled structure.

  As mentioned above, it is divided into (A) characteristics common to all people and (B) characteristics of each individual, and by adjusting only (B) for each individual, the configuration to realize appropriate out-of-head localization Also, canal type earphone can enjoy the sound field equivalent to the original sound field.

[Outside head localization filter for 'open headphone']
In the first embodiment, an equation for finding an out-of-head localization filter described in Non-Patent Document 1 is used. Therefore, first, these formulas will be described. In Non-Patent Document 1, it is assumed that the sound pressure at the tympanic membrane position is recorded and reproduced by headphones. To hear the same sound as the free field in headphone listening, using the out-of-head localization filter G _A, the following equation (3) needs to hold. That is, the transfer function of the sound pressure P _{1 at} the head center position when there is no dummy head or listener in the free sound field, and the sound pressure P _{4 at} the tympanic position of the dummy head or listener in the free sound field. the ratio, the sound pressure P _1, when the headphones listening, it is equal required ratio of the transfer function of the sound pressure P ₇ of the eardrum of the listener. Mike has a transfer function M _1, if the outside-head localization filter for equivalent of free-field and the headphone listening and G _A, the following equation (3) holds.

なお、式（３）に用いられる記号は以下の通りである。
Ｇ_Ａ：音圧Ｐ_４を用いた場合の、自由音場とヘッドホン受聴を等価にするための頭外定位フィルタ
Ｐ_１：自由音場における、ダミーヘッドあるいは受聴者が存在しない場合の頭部中心位置の音圧
Ｐ_４：自由音場における、ダミーヘッドあるいは受聴者の鼓膜位置の音圧
Ｐ_７：ヘッドホン受聴時における、受聴者の鼓膜位置の音圧
Ｍ_１：録音時のマイクロホン伝達関数
Ｅ_{ｈｅａｄｐｈｏｎｅ}：ヘッドホン端子電圧

In addition, the symbol used for Formula (3) is as follows.
G _A : Out-of-head localization filter P ₁ for equalizing free sound field and headphone listening when sound pressure P ₄ is used: Center of head in case free head or dummy head in free sound field does not exist sound pressure position _{P 4:} the free-field sound of the eardrum position of the dummy head or the listener pressure _{P 7:} when headphones listening the sound of the eardrum of the listener pressure _{M 1:} during recording microphone transfer function _{E headphone} : Headphone terminal voltage

However, since recording at the tympanic membrane position is not realistic, expression (3) can be expressed using the sound pressure P ₂ at the entrance position of the dummy head or the listener's closed ear canal in the free sound field. It becomes.

なお、式（４）に用いられる記号は以下の通りである。
Ｇ_ｃ：音圧Ｐ_２を用いた場合の、自由音場とヘッドホン受聴を等価にするための頭外定位フィルタ
Ｐ_１：自由音場における、ダミーヘッドあるいは受聴者が存在しない場合の頭部中心位置の音圧
Ｐ_２：自由音場における、ダミーヘッドあるいは受聴者の閉塞された外耳道入口位置の音圧
Ｐ_４：自由音場における、ダミーヘッドあるいは受聴者の鼓膜位置の音圧
Ｐ_７：ヘッドホン受聴時における、受聴者の鼓膜位置の音圧
Ｍ_１：録音時のマイクロホン伝達関数
Ｅ_{ｈｅａｄｐｈｏｎｅ}：ヘッドホン端子電圧

In addition, the symbol used for Formula (4) is as follows.
G _c : Out-of-head localization filter P ₁ for equalizing free sound field and headphone listening when sound pressure P ₂ is used: Center of head in case free head or dummy head in free sound field does not exist Sound pressure P _{2 of} position: Sound pressure P ₄ of the dummy head or the closed position of the ear canal at the free sound field P ₄ : Sound pressure of dummy head or eardrum position of the listener in free sound P ₇ : Headphones Sound pressure M ₁ of the eardrum position of the listener at the time of listening: Microphone transfer function at the time of recording E _headphone : headphone terminal voltage

When Equation (4) is transformed, the out-of-head localization filter G _c can be expressed by Equation (5).

In addition, the symbol used for Formula (5) is as follows.
G _c : Out-of-head localization filter P ₁ for equalizing free sound field and headphone listening when sound pressure P ₂ is used: Center of head in case free head or dummy head in free sound field does not exist Sound pressure at position P ₂ : Sound pressure at dummy head or listener's closed ear canal entrance position in free sound field P ₃ : Sound pressure at dummy head or listener's open ear canal entrance position in free sound field P ₄ : Sound pressure of the dummy head or eardrum's position of the listener in free sound field P ₅ : Sound pressure of the closed entrance of the ear canal at the time of headphone listening P ₆ : The listener's at the time of headphone listening sound pressure of the opened ear canal entrance point _{P 7:} when headphones listening the sound of the eardrum of the listener pressure _{M 1:} during recording microphone transfer function _{E headphone} Headphone jack voltage

In the equation (5), the first term [(P ₄ / P ₃ ) / (P ₇ / P ₆ )] on the right side represents the denominator (P ₇ / P ₆ ), the numerator (P ₇ / P ₆ ) when the recorder and the listener are the same. P ₄ / P ₃ ) both represent the same ear canal transfer function. Therefore, the first term on the right side is 1. The third term [1 / M ₁ (P ₇ / E _headphone )] on the right side requires the characteristics of the microphone, but if the same microphone as that used when measuring the sound pressure P ₅ is used, the equation (6) _Is expressed as a ratio between the headphone terminal voltage E _headphone and the microphone terminal voltage E _microphone . Therefore, the third term on the right side is determined by the voltage ratio, that is, the magnitude of the volume.

Ｅ_{ｈｅａｄｐｈｏｎｅ}：ヘッドホン端子電圧
Ｅ_{ｍｉｃｒｏｐｈｏｎｅ}：マイクロホン端子電圧
Ｇ：式（５）の右辺第３項

E _headphone : headphone terminal voltage E _microphone : microphone terminal voltage G: right side third term of equation (5)

The first term [(P ₄ / P ₃ ) / (P ₇ / P ₆ )] on the right side of equation (5) is 1, and the third term [1 / M ₁ (P ₇ / E _headphone )] on the right side is the volume. Is determined by the size of the Therefore, as long demanded equation right side of (5) the second term _{[(P 3 / P 2)} / (P 6 / P 5)], Out-of-head localization filters _{G c} is obtained. Here, the second term of the right side of the equation (5) is represented by the equation (1) shown below from FIG. 12 and FIG.

Ｐ_２：自由音場における、ダミーヘッドまたは受聴者の閉塞された外耳道入口位置の音圧
Ｐ_３：自由音場における、ダミーヘッドまたは受聴者の開放された外耳道入口位置の音圧
Ｐ_５：ヘッドホン受聴時における、受聴者の閉塞された外耳道入口位置の音圧
Ｐ_６：ヘッドホン受聴時における、受聴者の開放された外耳道入口位置の音圧
Ｚ_{ｅａｒ ｃａｎａｌ}：外耳道入口から鼓膜側を見た音響インピーダンス
Ｚ_{ｈｅａｄｐｈｏｎｅ}：ヘッドホン受聴時に外耳道入口から外側を見た音響インピーダンス
Ｚ_{ｒａｄｉａｔｉｏｎ}：自由音場で外耳道入口から外側を見た音響インピーダンス

P ₂ : Sound pressure of dummy head or listener's closed ear canal entrance position in free sound field P ₃ : Sound pressure of dummy head or listener's open ear canal entrance position in free sound field P ₅ : Headphones Sound pressure P ₆ of the closed ear canal entrance position of the listener at the time of listening: Sound pressure Z _{ear canal} of open _{ear canal} entrance position of the listener at the time of headphone listening: acoustic impedance seen from the _{ear canal} entrance Z _headphone : Acoustic impedance seen from the entrance of the ear canal at the time of headphone listening Z _radiation : Acoustic impedance seen from the entrance of the ear canal at free sound field

The right side of Equation (1) is 1 if the acoustic impedance Z _headphone is equal to the acoustic impedance Z _radiation . That is, this is the case for the condition of 'open headphone'. In this case, the out-of-head localization filter G _c can be obtained only by the equation (6).

[Outside head localization filter]
Here we focus on the earphones. There is also an open type of earphone called innaire, but since there are a lot of sound leaks, in recent years the canal type earphone has dominated the majority. However, since the acoustic impedance of the canal type earphone and the acoustic impedance of the free sound field are largely different, setting the ratio of equation (1) to 1, that is, satisfying the condition of 'open headphone' is the structure as described above. Above, it is difficult to realize.

  Therefore, in the first embodiment, the second term of the right side of Formula (1), that is, Formula (5) is obtained by measurement. For that purpose, the microphone position is not the ear canal inlet shown in Patent Document 1 or the tympanic position of the dummy head, but the positions as shown in FIGS. 1 to 4. 1 to 4 are views for explaining the concept of the extra-head localization filter, and more specifically, conceptually show an arrangement for measuring a sound pressure.

  The earphone 5 is provided with an earpiece 5a. The earphone 5 is attached to the ear 3 by inserting the earpiece 5 a into the inside of the ear canal 9. The microphone 1 for collecting the sound from the speaker of the earphone 5 is mounted on the near side of the eardrum 4 (the entrance side of the ear canal 9) and on the back side (the eardrum 4 side) of the mounting position of the earphone 5. That is, as shown in FIGS. 1 to 4, the microphone 1 is attached at a position between the eardrum 4 and the earphone 5 in the ear canal 9.

In FIGS. 1 and 3, the microphone 1 is fixed in the ear canal 9 by the ear plug 2. On the other hand, in FIG. 2 and FIG. 4, the earplug 2 is removed, and the microphone 1 is not fixed in the ear canal 9. Each sound pressure _P 2 of Non-Patent Document _{1, P 3, P 5,} P 6 , in the canal type earphone, the sound pressure _P 2e of the microphone positions of FIGS. 1 to _{4, P 3e, P 5e,} P It will be _6e .

  The installation position of the microphone 1 is preferably about 0.5 to 1 cm from the tip of the earpiece 5a. The reason why this position is desirable is as follows. The slightly crooked S-shaped characteristics to the tympanic position are different for each individual. Therefore, by setting this distance to 1 cm or less, only a short portion that can be regarded as a complete cylinder can be used. Then, both the dummy head and the human can be regarded as having the same characteristics only in this section. If the width is 0.5 cm or less, the earphones 5 and the microphone 1 become too close, making installation difficult and making appropriate sound collection measurement difficult.

Thus, by measuring the sound pressure _{P 2e, P 3e, P 5e} , the _{P 6e} using a dummy head for each earphone, it is possible to calculate the ratio of the sound pressure shown in equation (1). Then, from the sound pressure ratio of Equation (1), it is possible to obtain the earphone external localization filter _Gce using Equation (5). Doing sound pressure _{P 2e, P 3e, P 5e} , the measurement of _{P 6e} same earpiece 5, as described above, the first term becomes 1 of the formula (5), the third term as shown in Equation (6) The ratio between the headphone terminal voltage E _headphone and the microphone terminal voltage E _microphone is determined by the magnitude of the volume. That is, the sound pressure _P 2e was determined by _measuring, by a P _3e, the sound pressure of the formula P _5e, the _{P 6e} respectively _{(5) P 2, P 3} , P 5, P 6, of formula (5) The out-of-head localization filter G _c becomes the out-of-head localization filter G _{ce of the} earphone 5. In this manner, the universal out-of-head localization filter G _ce for the earphones 5 can be easily obtained. The earphone external localization filter _GC is the same as in the case of an earphone of the same type (mass-produced same type product).

5 to 8 show device configurations for measuring the sound pressure. Apparatus shown in FIGS. 5-8 is a filter generator 100 for generating a head outside localization filter G _ce for performing out-of-head localization process in the case of using the earphone 5. The filter generation device 100 includes a microphone 1, an earplug 2, a measurement tube 6, a speaker 8, and a processing device 10.

5 shows the sound pressure P _2e , FIG. 6 the sound pressure P _3e , FIG. 7 the sound pressure P _5e , and FIG. 8 the sound pressure P _6e . These sound pressures correspond to P _2, P _3, P _{5, and} P ₆ in Non-Patent Document 1, respectively.

  Here, the positions of the microphone 1 and the earphone 5 in the filter generation device 100 will be described. 1 and 2 show the canal-type earphone 5 not attached to the ear 3 and FIGS. 3 and 4 show the earphone 5 attached to the ear 3. The installation position of the microphone 1 is preferably a distance of 0.5 to 1 cm from the tip of the earpiece 5a.

Furthermore, the left side of equation (1) can be modified as equation (7).

Since P ₃ and P ₆ are sound pressures at the open ear canal entrance position, they contain the characteristics of the ear canal respectively, but if the recorder and the listener are identical, (P ₃ / P ₆ ) is the listener's Indicates that the characteristics of the ear canal are offset. Similarly, (P ₅ / P ₂ ) indicates that the characteristics of the ear canal of the listener are offset. Thus, neither the dummy head nor the S-shaped tube mimicking human ear canal characteristics need be used. From this, each sound pressure can be easily measured using an ear canal with eardrum, that is, a cylinder closed at one end and having a tube similar in size, length and material to the ear canal. it can.

  The measuring tube 6 is shaped like a test tube and comprises a straight tube portion 6b. The measuring pipe 6 is provided with an open port 6a at one end. The straight pipe portion 6b has a straight cylindrical shape. That is, the straight pipe portion 6b is circular in cross section and constant. Then, one end of the straight pipe portion 6b is an open port 6a.

  The measuring tube 6 is made of a material having the same characteristics as the human ear canal. The measuring tube 6 is an ear canal-like cylinder like a test tube similar in size, length and material to that of the ear canal. The measuring tube 6 is formed of, for example, a silicone resin. The portion of the ear canal that corresponds to the tympanic membrane, i.e., the bottom of the ear canal-like cylinder, is perforated so that the microphone cable 7 can pass through, and is covered with clay or the like. The measuring tube 6 has, for example, a length of 3 cm and a diameter (inner diameter) of 6 mm.

  The microphone 1 is installed inside the measurement tube 6. The microphone 1 is installed in the straight pipe portion 6b. The positions of the microphones 1 are all the same in FIGS. The inner diameter of the measuring tube 6 is as large as that of the human ear canal. The microphone 1 is sized to fit in the measurement tube 6. The microphone 1 outputs a signal collected through the microphone cable 7 to the processing device 10. The microphone cable 7 of the microphone 1 is taken out of the other end of the measurement tube 6 to the outside of the measurement tube 6. The processing device 10 is a signal processing device provided with an A / D converter, a memory, a processor and the like.

  In FIGS. 5 and 7, the microphone 1 is fixed to the measurement tube 6 by the ear plug 2. The earplug 2 covers the microphone 1. The microphone 1 is fixed by fitting the earplug 2 to the measurement tube 6. The earplug 2 is sized to close the measuring tube 6. The earplug 2 may be of the same type as the earpiece 5a used for the canal type earphone 5. On the other hand, in FIG. 6 and FIG. 8, the ear plug 2 is removed, and the microphone 1 is not fixed to the measurement tube 6. That is, in FIG. 6 and FIG. 8, the microphone 1 is in a floating state in the measurement tube 6.

In FIGS. 5 and 6, the earphone 5 is not attached to the measurement tube 6, and the speaker 8 as a sound source is provided outside the measurement tube 6. In FIGS. 5 and 6, the microphone 1 measures the sound pressure when the speaker 8 is driven. The signal collected by the microphone 1 is input to the processing device 10 via the microphone cable 7. Thereby, sound pressure _P2e and sound pressure _P3e are measured. The position (angle and distance) of the speaker 8 is not particularly limited, but preferably 50 to 100 cm away from the microphone 1 in consideration of measurement accuracy. As shown in FIG. 5, the microphone 1 is installed without being fixed to the measurement tube 6 by the ear plug 2, and the sound pressure of the free sound field is measured when the speaker 8 is driven without attaching the earphone 5 to the measurement tube 6 And the sound pressure P _{2 e} . As shown in FIG. 6, the microphone 1 is fixed to the measuring tube 6 by the ear plug 2 and the microphone 1 measures the sound pressure of the free sound field when the speaker 8 is driven without attaching the earphone 5 to the measuring tube 6 Sound pressure P 3 _e .

As shown in FIGS. 7 and 8, a canal-type earphone 5 is attached to the opening 6a of the measuring tube 6. Here, it is preferable that the earpiece 5 a of the earphone 5 be mounted so as to completely enter the measuring tube 6. The earpiece 5a is preferably the same size as the earplug 2 and can be fitted into the opening 6a of the measuring tube 6. As shown in FIG. 7, the microphone 1 is installed without being fixed to the measurement tube 6 by the ear plug 2, and the sound pressure when the earphone 5 is driven is measured by the microphone 1 as a sound pressure P 5 _e . As shown in FIG. 8, the microphone 1 is fixed to the measurement tube 6 with the ear plug 2, and the sound pressure when the earphone 5 is driven is measured by the microphone 1 and is used as the sound pressure P _{6 e} .

In FIG. 7 and FIG. 8, the earphone 5 is a sound source. The microphone 1 measures the sound pressure when the earphone 5 is driven. The microphone 1 outputs the collected signal to the processing device 10 via the microphone cable 7. The sound pressure P _5e and the sound pressure P _6e are measured by the above processing.

In the configurations of FIGS. 5 to 8, for example, the earphone 5 or the speaker 8 generates an impulse signal. Then, when the microphone 1 is to measure the impulse response, the sound pressure _{P 2e,} the sound pressure _{P 3e,} the sound pressure _{P 5e,} the sound pressure _{P 6e} is measured. Then, the measured sound pressure _{P 2e,} the sound pressure _{P 3e,} the sound pressure _{P 5e,} the sound the sound pressure _{P 2} of the pressure _{P 6e} Equation (5), and (7), the sound pressure _{P 3,} the sound pressure _{P 5,} sound used as pressure _{P 6.} In addition, the order to measure is not specifically limited. The microphone 1, the earphone 5, and the speaker 8 used for the measurement are common.

The processing device 10 is an information processing device provided with a memory, a processor, and the like. The processing device 10 stores the sound pressure P _2e , the sound pressure P _3e , the sound pressure P _5e , and the sound pressure P _6e in a memory or the like. After four sound pressure is measured, the processing unit 10, the sound pressure _{P 2e,} the sound pressure _{P 3e,} the sound pressure _{P 5e,} on the basis of the sound pressure _{P 6e,} calculates the out-of-head localization filter. For example, processor 10, the ratio of the sound pressure of the formula _{(1) (P 3e / P} 2e) / Request _(P 6e _/ P _5e). Then, the processing unit 10, by substituting the ratio of sound pressure in Equation (5), calculates the out-of-head localization filter G _ce. Since the sound pressure ratio, that is, the out-of-head localization filter is a value unique to the earphones, it may be measured for each earphone. The same value can be used for the same type of earphone.

Thus, by measuring the four microphone sound pressure can be obtained easily-head localization filter G _ce. As described above, the third term of the equation (5) is actually expressed as a level (volume) because it is a voltage ratio as shown by G in the equation (6).

  The measuring tube 6 is shaped to have a hole diameter similar to that of the ear hole. It is desirable that the equation (1) be accurately determined from the equation (5), and the earpiece 5a be mounted so as to be completely fitted in the ear canal or the measuring tube 6. Therefore, it is necessary to attach an earpiece 5 a of the same size as the ear canal and the measuring tube 6. By doing this, the sound path becomes exactly parallel to the ear canal, and the signal is transmitted as one-dimensional vibration.

In the first embodiment, a cylinder in which the ear canal is modeled is used as the measurement tube 6. That is, a cylinder whose one end is open and whose other end is closed is used as the measurement pipe 6. A straight pipe portion 6 b is provided on the side of the opening 6 a of the measuring pipe 6. The sound pressure is measured by the microphone 1 installed in the straight pipe portion 6b. By doing this, since sound is transmitted as one-dimensional vibration, it is possible to measure the sound pressure while eliminating individual differences in the S-shaped portion of the ear canal. Therefore, the universal out-of-head localization filter _GC can be obtained. In addition, as long as the measurement pipe 6 in which the straight pipe portion 6b is provided, the shape thereof is not particularly limited.

Moreover, it is preferable to install a microphone at a position of 0.5 to 1 cm from the tip of the earpiece 5a in a state in which the entire earpiece 5a is closely fitted along the ear canal. In this way, it is possible to obtain the universal out-of-head localization filter _GCe not by individuals but through measurements. Generally, all the people from the entrance of the ear canal to 1 cm are almost straight pipes in common. Therefore, in the case of earphones of the same type, the common out-of-head localization filter _GC can be used. In other words, the out-of-head localization filter can be determined without depending on the shape of the ear canal of the user of the earphone. In addition, since the dummy head is also unnecessary, the sound pressure can be measured easily. Furthermore, since the characteristics of the left and right ears are common, it is possible to obtain the left and right extracorporeal localization filters _GCe by one measurement.

Then, for the earphones 5 of the same type, the common extracorporeal localization filter _GC can be used. That is, by performing measurement on a certain earphone 5, individual measurement of the same type earphone as that earphone 5 becomes unnecessary. For the different types of earphones, similar sound pressure measurement can be performed to obtain the out-of-head localization filter G _ce specific to the type of earphones.

[Outside head localization processing]
Next, the configuration of the out-of-head localization processing apparatus 20 that performs out-of-head localization processing will be described using FIG. The out-of-head localization processing device 20 performs a filtering process for out-of-head localization when using an earphone. The out-of-head localization processing apparatus 20 includes convolution calculation units 11 to 14, a correction processing unit 15, a sound quality adjustment unit 16, a frequency sweep signal generator 17, a switch 18, and an adder 19. In addition, in FIG. 9, L is attached | subjected to the code | symbol about the structure corresponding to the earphone of the left, and R is attached | subjected to the code | symbol about the structure corresponding to the earphone of the right.

  The left and right stereo input signals SL and SR are input to the out-of-head localization processing device 20. The stereo input signals SL and SR are stereo signals output from a CD player or the like. The switch 18 switches between the stereo input signals SL and SR and the frequency sweep signal SIG from the frequency sweep signal generator 17. The stereo input signal SL is an input signal of the left channel, and the stereo input signal SR is an input signal of the right channel. The frequency sweep signal SIG is used to adjust personal characteristics. The frequency sweep signal SIG will be described later.

  In the convolution operation unit 11, a transfer function Hls from the L speaker to the entrance of the left external ear canal is set. The convolution operation unit 11 performs a convolution operation using the transfer function Hls on the stereo input signal SL. In the convolution operation unit 12, a transfer function Hlo from the L speaker to the entrance of the right external ear canal is set. The convolution unit 12 performs a convolution operation on the stereo input signal SL using the transfer function Hlo.

  In the convolution unit 13, a transfer function Hro from the R speaker to the entrance of the left ear canal is set. The convolution operation unit 13 performs a convolution operation using the transfer function Hro on the stereo input signal SR. In the convolution operation unit 14, a transfer function Hrs from the R speaker to the entrance of the right external ear canal is set. The convolution unit 14 performs a convolution operation on the stereo input signal SR using a transfer function Hrs.

  As for the transfer functions of the convolution calculation units 11 to 14, it is preferable to use a head-related transfer function of the characteristics of the listener. For example, a head-related transfer function can be obtained by impulse response measurement using a stereo speaker as a sound source. The same microphone position characteristics as in FIG. 1 are desirable, but microphone placement is difficult. Therefore, the microphone is installed at the position just at the entrance of the ear canal and measurement is performed. From this position to the microphone position of FIG. 1 may be considered as one-dimensional vibration. Then, four transfer functions are obtained from the measurement result of the microphone 1. For example, the transfer function can be obtained by impulse response measurement using each of the stereo speakers as a sound source. Alternatively, a plurality of head related transfer functions may be preset in a storage unit (not shown), and a head related transfer function having characteristics close to the listener may be selected from the presets and used. The storage unit stores a head-related transfer function based on the measurement result of the impulse response measured by the dummy head or another listener. This eliminates the need for impulse response measurement in the state where the listener is wearing the microphone.

  The convolution operation units 11 and 13 output the convolution operation data subjected to the convolution operation process to the adder 19L. The adder 19L adds the two convolution operation data, and outputs the result as an addition signal to the correction processing unit 15L. The convolution operation units 12 and 14 output the convolution operation data subjected to the convolution operation process to the adder 19R. The adder 19R adds two convolution operation data, and outputs the result as an addition signal to the correction processing unit 15R.

Correction processing unit 15L, 15R, using the out-of-head localization filter _{G ce,} performs correction processing on the addition signal. In other words, the correction processing unit 15L, respectively 15R, relative calculation result of the convolution operation unit 11 to 14, performs correction using the out-of-head localization filter _{G ce.} Incidentally, Out-of-head localization filters G _ce are those calculated based on the sound pressure measurement result in the out-of-head localization filter generator 100 shown in FIGS. 5 to 8.

  The sound quality adjusting units 16L and 16R respectively adjust the sound quality of the signals corrected by the correction processing units 15L and 15R. The sound quality adjustment unit 16 has a filter that changes the gain according to the frequency. Specifically, the sound quality adjustment unit 16 has a notch filter and a peaking filter. The sound quality adjustment unit 16 can change the gain for each frequency band. The sound quality adjustment unit 16 adjusts the sound quality in accordance with the resonance frequency. The resonant frequency changes according to the shape of the ear canal of the listener. That is, there are individual differences in resonance frequency. Therefore, the sound quality adjustment unit 16 has a filter according to the listener. In the first embodiment, a filter corresponding to a listener is set by adjustment using the frequency sweep signal SIG. Hereinafter, a method of adjusting the resonance frequency in the sound quality adjustment unit 16 will be described.

[Adjustment of resonance frequency]
Characteristic resonance occurs in the straight tube portions of the microphone 1 and the earphone 5 placed 0.5 to 1 cm from the tip of the earpiece 5a. Therefore, the sound quality may change depending on the resonance frequency. In order to avoid this, a notch filter group is required. Furthermore, the section from the microphone 1 to the eardrum of the listener is curved for each individual, and as a result, the resonance frequency is different. Therefore, the sound quality adjustment unit 16 adjusts the sound quality changed by the resonance in the above-mentioned notch filter group. Since this is a sound that can only be perceived by the listener, the out-of-head localization processing device 20 presents the frequency and determines the notch frequency at the timing of strong hearing. Conversely, frequencies that can not be heard at the tympanic membrane position also appear. Since the frequency which becomes hard to hear suddenly is known by reproducing the pure tone made to sweep also about this, it may be emphasized with a peaking filter.

  Personal characteristic adjustment in the sound quality adjustment unit 16 will be described with reference to FIGS. 10 and 11. FIG. 10 is a diagram schematically showing how personal characteristics are adjusted according to the listener. FIG. 11 is a flowchart showing a method of measuring personal characteristics. As shown in FIG. 10, an out-of-head localization processing apparatus 20 is used to set a filter according to personal characteristics. The earphones 5 are connected to the out-of-head localization processing device 20. The left and right earphones 5L and 5R are respectively attached to the left and right ears 3L and 3R of the listener U.

  The purpose of the personal characteristic adjustment in the sound quality adjustment unit 16 is to identify and correct the resonance caused by the ear canal. This resonance is caused by the characteristics of the listener's own ear canal. For this reason, as shown in FIG. 10, the listener U wears the earphone 5. The earphone 5 is the same as the earphone 5 used for sound pressure measurement. Then, while the listener U is listening to the sound with the earphone 5 as the sound source, the out-of-head localization processing device 20 adjusts the personal characteristics. At this time, as shown in FIG. 3 and the like, the listener U is worn in such a manner that the entire earpiece 5a of the earphone 5 is completely fitted in the ear hole.

  The listener U switches the input to the frequency sweep signal generator 17 at the switch 18 of FIG. The listener U listens to a frequency sweep signal mainly in the high frequency range. The frequency sweep signal is a pure tone, and is a signal whose center frequency gradually changes. The frequency sweep signal generator 17 generates a signal of frequency F = 5 kHz for 200 msec (S1). Next, the frequency sweep signal generator 17 generates a signal of F (5 kHz) + 10 Hz (S2). When the listener U hears the loudness of the latter sound (5 kHz + 10 Hz) larger than the former sound (5 kHz) (S3 → Yes), the display device 21 in which the listener U is provided in the external localization processing device 20 Lower the gain control bar. When the out-of-head localization processing device 20 receives an operation to lower the gain control bar, the sound quality adjustment unit 16 lowers the gain of the frequency with the notch filter (S4).

  When the listener U does not feel that the volume of the latter sound (5 kHz + 10 Hz) is higher than that of the former sound (5 kHz) (S3 → No), the listener U does not adjust the gain and takes the same volume. When the listener U does not feel that the volume is high (S3 → No) or when the sound quality adjustment unit 16 lowers the gain in S4, the listener U compares the former sound (5 kHz) with the latter sound (5 kHz + 10 Hz) It is judged whether the volume of is low (S5). If the listener U feels that the volume is small (S5 → Yes), the listener U raises the gain control bar of the display device 21 provided in the extra-head localization processing device 20. When the out-of-head localization processing device 20 receives an operation to raise the gain control bar, the sound quality adjustment unit 16 raises the gain of the frequency with the peaking filter (S6). Then, the sound quality adjustment unit 16 repeats the processes of steps S3 to S6 until the gain of the frequency F becomes an appropriate value.

  If the listener U does not feel that the volume is particularly low (S5 → No), the process proceeds to S7. If the frequency F is smaller than 20 kHz (S7-> Yes), the process returns to S2, and the frequency sweep signal generator 17 generates a signal in which the frequency F is increased by 10 Hz. If the frequency F is 20 kHz or more, the sound quality adjustment unit 16 ends the processing (S7 → No). Thus, the frequency sweep signal in which the frequency F changes gradually is outputted, and the processing is performed until the gain for each frequency becomes appropriate.

  If the listener U hears any frequency of 5 kHz to 20 kHz with substantially equal magnitude, the personal characteristic adjustment ends. It is desirable that the frequency generated by the frequency sweep signal generator 17 be displayed on the display device 21 so that the listener U can easily determine. The listener U may be made to adjust the speed at which the frequency sweep signal generator 17 sweeps the frequency. The frequency range to be swept is preferably started from 5 kHz or more from the mechanism of the ear canal resonance (the lowest resonance frequency is 5667 Hz in the case of an ear canal 30 mm in length), and the adjustment frequency is 8 kHz or more It is also good. Of course, the entire reproduction frequency range of the canal type earphone may be targeted. Also, the listener U may designate the frequency to be adjusted.

  It is preferable to perform personal characteristic adjustment for each listener. After the personal characteristic adjustment, a filter having a gain corresponding to the frequency is set in the sound quality adjustment unit 16. The out-of-head localization processing device 20 switches the changeover switch 18 to the stereo input signals SL and SR, and the listener listens to music. At this time as well, the same earphone 5 of the same type as the earphone 5 whose sound pressure was measured as shown in FIGS. 5 to 8 is mounted so that the entire earpiece completely fits in the ear hole. As a result, the generated out-of-head localization filter is accurately reproduced, and even a canal type earphone can enjoy a sound field equivalent to the original sound field. Alternatively, the sound quality adjusting unit 16 may store the filter set by the personal characteristic adjustment in the storage unit (not shown) in association with the listener. At the time of listening, the listener selects a filter for personal use. By so doing, the sound quality adjustment unit 16 can perform sound quality adjustment according to the listener and perform appropriate out-of-head localization processing.

By the microphone installed in the measurement tube 6 imitating the inside of the ear canal, it is possible to obtain the universal out-of-head localization filter _GCe for all the earphones 5 not depending on the individual. It is preferable to set the microphone 1 0.5 to 1 cm from the tip of the earpiece 5a. By doing this, an out-of-head localization filter can be appropriately obtained. Furthermore, by using the earphone 5 in which the entire earpiece 5a is fitted in the earhole, it is possible to accurately apply the obtained out-of-head localization filter.

After obtaining the universal out-of-head localization filter _GCe by measurement using the measuring tube 6, the out-of-head localization filter _GCe is corrected in accordance with the personal characteristics of the listener. That is, the sound quality adjustment unit 16 adjusts the sound quality according to the listener. The sound quality adjusting unit 16 includes a notch filter and a peaking filter which are set according to the listening result of the listener U when the listener U outputs a sweep signal whose frequency changes in a state where the earphone 5 is worn. . The listener can enjoy sound field reproduction equivalent to the current sound field also in the earphone by finely adjusting the resonance with the notch filter and the peaking filter. From the above, it is possible to obtain a universal out-of-head localization filter for everyone, and even a canal type earphone can enjoy a sound field equivalent to the original sound field.

  The out-of-head localization processing device 20 and the processing device 10 may be physically the same device or different devices. When different devices are used, the generated filter or the out-of-head localization filter in the processing device 10 may be transferred to the out-of-head localization processing device 20.

Second Embodiment
Although the canal type earphone has been described in the first embodiment, an open type earphone (in-aiya type) is used in the second embodiment. Although non-patent document 1 describes that the equation (1) is close to 1 in the case of an open type headphone, the reproduction band and the reproduction volume of the earphone are not sufficient compared to the headphone but it is close to 1. Absent. Therefore, as in the first embodiment, the in-ear type external localization filter of in-ear type earphone is obtained by measurement. The sound quality adjustment unit 16 performs gain adjustment using a frequency sweep signal for the in-ear type earphone. By doing so, the same effect as that of the first embodiment can be obtained for the in-ear type earphone.

  Some or all of the above-described filter generation processing method and out-of-head localization processing method may be executed by a computer program. The programs described above can be stored and supplied to a computer using various types of non-transitory computer readable media. Non-transitory computer readable media include tangible storage media of various types. Examples of non-transitory computer readable media are magnetic recording media (eg flexible disk, magnetic tape, hard disk drive), magneto-optical recording media (eg magneto-optical disk), CD-ROM (Read Only Memory), CD-R, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory)) are included. Also, the programs may be supplied to the computer by various types of transitory computer readable media. Examples of temporary computer readable media include electrical signals, light signals, and electromagnetic waves. The temporary computer readable medium can provide the program to the computer via a wired communication path such as electric wire and optical fiber, or a wireless communication path.

  As mentioned above, although the invention made by the present inventor was concretely explained based on an embodiment, the present invention is not limited to the above-mentioned embodiment, and can be variously changed in the range which does not deviate from the gist. Needless to say.

Reference Signs List 1 microphone 2 earplug 3 ear 4 eardrum 5 earphone 5a earpiece 6 measurement tube 6a open port 6b straight tube portion 7 microphone cable 8 speaker 9 external ear canal 10 processing device 11-14 convolution operation unit 15 correction processing unit 16 sound quality adjustment unit 17 frequency sweep signal Generator 20 Head Localization Processor 100 Filter Generator

Claims (10)

A measuring pipe having a straight pipe portion,
A microphone provided at the straight pipe portion in the measurement pipe;
An earplug for securing the microphone to the measurement tube;
An earphone attached to the measurement tube;
A speaker installed outside the measurement tube;
A processing unit that generates an out-of-head localization filter based on the first sound pressure, the second sound pressure, the third sound pressure, and the fourth sound pressure;
Equipped with
The microphone is installed without being fixed to the measurement tube by the earplug, and the microphone measures the sound pressure of a free sound field when the speaker is driven without attaching the earphone to the measurement tube. The first sound pressure,
The microphone is fixed to the measurement pipe with the earplug, and the microphone measures the sound pressure of a free sound field when the speaker is driven without attaching the earphone to the measurement pipe, and the second sound is generated. Pressure,
The microphone is installed without being fixed to the measurement tube by the earplug, and the sound pressure when the earphone is driven is measured by the microphone to be the third sound pressure.
The out-of-head localization filter generating device, wherein the microphone is fixed to the measurement pipe with the earplug, and the sound pressure when the earphone is driven is measured as the fourth sound pressure by the microphone.   The out-of-head localization filter is calculated based on a value of (the first sound pressure / the second sound pressure) / (the third sound pressure / the fourth sound pressure). Out-of-head localization filter generator.   The out-of-head localization filter generating device according to claim 1 or 2, wherein the installation position of the microphone is 0.5 to 1 cm from the tip of the earpiece of the earphone. A convolution unit that convolutes a head related transfer function to the left channel signal and the right channel signal;
A correction processing unit that corrects the calculation result of the convolution calculation unit using the out-of-head localization filter generated by the out-of-head localization filter generation device according to any one of claims 1 to 3;
A sound quality adjustment unit that performs sound quality adjustment according to personal characteristics of the listener on the signal corrected by the correction processing unit;
4. An extra-head localization comprising: an earphone of the same type as the earphone used in the extra-head localization filter generation device according to any one of claims 1 to 3 and outputting a signal adjusted by the sound quality adjustment unit. Processing unit. The sound quality adjustment unit outputs the sweep signal whose frequency changes in a state where the listener who outputs the signal adjusted by the sound quality adjustment unit wears the earphone, according to the listening result of the listener It has multiple filters set up,
The out-of-head localization processing device according to claim 4, wherein the sound quality adjustment unit changes the gain according to a frequency using the plurality of filters. Measuring a first sound pressure, a second sound pressure, a third sound pressure, and a fourth sound pressure using a measuring tube, a microphone, an earplug, an earphone, and a speaker;
Generating an out-of-head localization filter based on the first sound pressure, the second sound pressure, the third sound pressure, and the fourth sound pressure;
Equipped with
The measuring pipe has a straight pipe portion,
The microphone is provided at the straight pipe portion in the measurement pipe,
Securing the earplug and the microphone to the measuring tube;
The earphone is attached to the measuring tube,
The speaker is installed outside the measuring tube,
The microphone is installed without being fixed to the measurement tube by the earplug, and the microphone measures the sound pressure of a free sound field when the speaker is driven without attaching the earphone to the measurement tube. The first sound pressure,
The microphone is fixed to the measurement pipe with the earplug, and the microphone measures the sound pressure of a free sound field when the speaker is driven without attaching the earphone to the measurement pipe, and the second sound is generated. Pressure,
The microphone is installed without being fixed to the measurement tube by the earplug, and the sound pressure when the earphone is driven is measured by the microphone to be the third sound pressure.
The out-of-head localization filter generating method, wherein the microphone is fixed to the measurement tube with the earplug, and the sound pressure when the earphone is driven is measured as the fourth sound pressure by the microphone.   The out-of-head localization filter is calculated based on a value of (the first sound pressure / the second sound pressure) / (the third sound pressure / the fourth sound pressure). Out-of-head localization filter generation method.   The method for generating an extra-head localization filter according to claim 6, wherein the installation position of the microphone is 0.5 to 1 cm from the tip of the earpiece of the earphone. A convolution operation step of convoluting a head related transfer function to the left channel signal and the right channel signal;
A correction step of correcting the calculation result in the convolution calculation step using the out-of-head localization filter generated by the out-of-head localization filter generation method according to any one of claims 6 to 8;
A sound quality adjustment step of performing sound quality adjustment according to personal characteristics of the listener on the signal corrected in the correction step;
An out-of-head localization process including the step of outputting the signal adjusted in the sound quality adjustment step from an earphone of the same type as the earphone used in the out-of-head localization filter generation method according to any one of claims 6 to 8. Method. A plurality of filters are set according to the listening result of the listener when the listener outputs the sweep signal whose frequency changes in a state where the listener wears an earphone that outputs the signal adjusted in the sound quality adjustment step. Further comprising steps,
10. The method according to claim 9, wherein in the sound quality adjustment step, the gain is changed according to the frequency using the plurality of filters.

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