JP2020031372A - Electroacoustic transducer - Google Patents

Abstract

To achieve a small, high-acoustic-quality, etc., electroacoustic transducer.SOLUTION: An electroacoustic transducer 30 includes: an equalizer 35 for inputting one of audio signals Sin of a stereo signal and outputting a changed audio signal by changing frequency characteristics of the audio signal Sin; and a driver unit 36 for converting the changed audio signal into an audio wave and outputs the audio wave to a user's ear. The equalizer 35 has impedance Z constituted by a parallel circuit of a resistor R and a capacitor C. In a low frequency range, a low-frequency reproduction sound pressure of the audio wave is reduced. In a high frequency region, a high-frequency reproduction sound pressure of the audio wave is relatively increased.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wide sound field and high-quality electro-acoustic transducer (for example, an earphone or headphones).

Electro-acoustic transducers such as earphones or headphones include a dynamic type, a magnetic type, a balanced armature type, a hybrid type, a piezoelectric type, a crystal type, an electrostatic type, and the like. There are ear type, canal type, headband type, neckband type, ear hanging type and clip type.
Patent Literature 1 discloses an earphone or headphones as an electroacoustic transducer. Patent Literature 2 discloses a headphone as an electroacoustic transducer.

  2. Description of the Related Art Conventionally, for example, a canal type earphone of a type in which an earpiece is inserted into an ear canal is provided with a housing including a driver unit which is an electric / sound converter for converting a sound signal into sound (sound wave), and is protruded from a front surface of the housing. It has a tubular sound conduit for guiding the sound wave, and an earpiece for insertion into an ear hole, which is attached to a distal end portion of the sound conduit. The driver unit includes a voice coil, a permanent magnet (magnet), a diaphragm (diaphragm), and the like.

FIG. 23 is a basic acoustic equivalent circuit diagram showing a conventional canal type earphone.
In this acoustic equivalent circuit, a sound signal sent from the sound source 1 is converted into a sound wave by the driver unit 2 and emitted to the ear canal 3. The driver unit 2 is represented by a simple oscillation system including a series circuit of an inductor Lo, a capacitor Co, and a resistor Ro. The input voltage Eout is applied to the driver unit 2. The ear hole 3 is represented as an acoustic capacitance Ce.

FIGS. 24A and 24B are frequency characteristic diagrams showing calculation examples when frequency characteristics are calculated by substituting appropriate circuit constants into the acoustic equivalent circuit of FIG. 23, and the horizontal axis is frequency (Hz). , And the vertical axis represents the input voltage Eout (dB) of the driver unit 2.
The waveform of the solid line in FIG. 24 is a waveform diagram when circuit constants (for example, Lo = 1 mH, Co = 10 μF, Ro = 15Ω, Ce = 0.7 μF) are substituted into the acoustic equivalent circuit of FIG. The dashed line waveform is a waveform diagram when circuit constants (for example, Lo = 0.6 mH, Co = 10 μF, Ro = 15Ω, Ce = 0.7 μF) are substituted into the acoustic equivalent circuit of FIG.

As is clear from FIG. 24, in a low frequency region equal to or lower than the resonance frequency of the driver unit 2, the equivalent circuit of the driver unit 2 is elastically controlled by the capacitance Co as shown in FIG. Becomes flat.
On the other hand, in a high-frequency region equal to or higher than the resonance frequency of the driver unit 2, the equivalent circuit of the driver unit 2 performs inertial control including the inductor Lo as shown in FIG. 24B, and the frequency characteristic is 12 dB per octave. It is attenuated, and the characteristics in the high frequency region are deteriorated. Actually, a peak indicated by a broken line occurs in the waveform of the solid line due to the influence of air column resonance or the like due to the shape of the housing accommodating the driver unit 2 or the like.
To improve the deterioration of the characteristics in the high frequency region as shown in FIG. 24B, it is necessary to reduce the mass of the driver unit 2, but it is actually difficult.

  As an improvement measure, for example, in the electro-acoustic transducer disclosed in Patent Document 1, a high-frequency enhancement including an LC series resonance circuit of an inductor L and a capacitor C is provided in a wiring cable for transmitting an audio signal connected to an input side of a driver unit. The circuit is incorporated to improve the sound pressure in the high frequency range and improve the characteristics in the high frequency range.

FIG. 25 is a circuit diagram showing a configuration example of a high-frequency enhancement circuit described in Patent Document 1.
A high-frequency enhancement circuit 10 is connected between the audio signal transmission wiring cord 5 and a driver unit (not shown). The wiring code 5 includes a left channel (hereinafter referred to as “Lch”) audio signal line 5a, a right channel (hereinafter referred to as “Rch”) audio signal line 5b, and a ground line 5c. The high-frequency enhancement circuit 10 is an LC series resonance circuit including an inductor Ll connected between the Lch audio signal line 5a and the ground line 5c, a switch SWl for switching capacitance, and two capacitors C11 and C21 having different capacitance values. And an LC series resonance circuit including an inductor Lr connected between the Rch audio signal line 5b and the ground line 5c, a switch SWr for switching capacitance, and two capacitances C1r and C2r having different capacitance values. ing.

FIG. 26 is a frequency characteristic diagram in which the high-frequency enhancement circuit 10 of FIG. 25 is connected to the input side of the driver unit. The horizontal axis represents the frequency (Hz), and the vertical axis represents the output side of the high-frequency enhancement circuit 10. Input voltage Eout (dB) of the input driver unit.
The solid line waveform of the circuit condition 1 in FIG. 26 is a waveform diagram when the switches SWl and SWr are switched to the capacitors C11 and C1r, and the broken line waveform of the circuit condition 2 in FIG. It is a waveform diagram at the time of switching to C21, C2r side.
As is clear from FIG. 26, the sound pressure of the input voltage Eout of the driver unit in the high-frequency region is improved by providing the high-frequency enhancement circuit 10.

Japanese Patent No. 5997806 JP 2009-141880 A

Published by Japan Broadcasting Corporation, “Broadcasting Technology Sosetsu 3 Broadcasting Acoustic Technology”, 3rd print (1983-6-1), Japan Broadcasting Publishing Association p. 20 Shinichiro Iwamiya, "Basics and Mechanism of Latest Sound [Understanding Basic Illustration [2nd Edition]", First Edition, 1st Edition (2014-4-10) Shuwa System Co., Ltd. p. 119

However, the conventional electroacoustic transducer described in Patent Literature 1 has the following problems.
In order for the high-frequency enhancement circuit 10 of FIG. 25 to work effectively, it is better that the DC resistances of the inductors Ll and Lr are small. In order to avoid the influence of the resistance of the wiring cord 5, the high-frequency enhancement circuit 10 needs to be installed as close to the sound source as possible. However, the inductors L1 and Lr having a small DC resistance and a required inductance value have large dimensions (sizes), so that it is difficult to reduce the size of the electroacoustic transducer. Therefore, it has been difficult to realize a small-sized electroacoustic transducer having a wide sound field and high sound quality.

An electroacoustic transducer according to a first aspect of the present invention is configured to receive one of a stereo signal having a pair of left and right in-phase first and second audio signals, and to input the audio signal. And a driver unit for converting the frequency characteristic of the sound signal to output a changed sound signal, and converting the changed sound signal into a sound wave and outputting the sound wave to a user's ear.
The equalizer has an impedance Z constituted by a parallel circuit of a resistor R and a capacitor C. In a low frequency region, the low frequency reproduction sound pressure of the sound wave is obtained by a signal voltage drop Vo obtained from the following equation (1). Lower,
Vo = R / (R + Zd) (1)
Zd: impedance of the driver unit (represented by resistance)
In the high frequency region, the capacitance C eliminates the signal voltage drop Vo and relatively increases the high-frequency reproduction sound pressure of the sound wave.

An electroacoustic transducer according to a second invention is constituted by a parallel circuit of a first resistor and a first capacitor, and the first audio of the stereo signal having a pair of left and right in-phase first audio signals and second audio signals. A first equalizer for receiving a signal and changing a frequency characteristic of the first sound signal to generate a changed sound signal; and a series circuit of a second resistor and a second capacitor, and receiving the second sound signal. A second equalizer that adds the second audio signal to the changed audio signal in an opposite phase, and converts a synthesized signal of the changed audio signal and the second audio signal having the opposite phase into a sound wave and outputs the sound wave to a user's ear. And a driver unit that performs the operation.
The electroacoustic transducer is, for example, an earphone or a headphone.

  According to the electroacoustic transducer of the first aspect, since the equalizer having the impedance constituted by the parallel circuit of the resistor and the capacitor is provided, the relative frequency of the high frequency region is changed depending on the resistance and the capacitance of the equalizer. Characteristics can be easily improved. Furthermore, an equalizer configured by a parallel circuit of a resistor and a capacitor is smaller and less expensive than an equalizer configured by a conventional series circuit of an inductor and a capacitor.

  According to the electroacoustic transducer of the second aspect, the first equalizer configured by the parallel circuit of the first resistor and the first capacitor, the second equalizer configured by the series circuit of the second resistor and the second capacitor, Since the second audio signal is added in reverse phase from the first audio signal to the modified audio signal generated by the first equalizer by the second equalizer, the sound field can be adjusted. . The adjustment amount and frequency characteristics of the sound field can be easily changed and adjusted by the values of the capacitance and resistance of the first and second equalizers. Therefore, it is smaller and less expensive than the conventional change and adjustment based on the values of the inductor and the capacitance.

1 is a schematic configuration diagram illustrating an electroacoustic transducer (for example, a canal type earphone) according to a first embodiment of the present invention. Frequency characteristic diagram of input voltage Eout applied to driver unit 36 of earphone 30 in FIG. Diagram showing stereo listening with speakers Diagram for explaining localization of sound image of stereo signal reproduction by speaker Diagram for explaining the relationship between the localization of a sound image and the signal in stereo signal reproduction by a speaker Diagram for explaining localization of sound image of stereo signal reproduction by earphone Diagram for explaining localization of sound image of stereo signal reproduction by actual earphone Diagram showing the change in the transmission frequency characteristic up to the ear canal entrance depending on the direction of the sound source in the median plane Diagram showing front localization in directional localization Diagram showing rearward and upward localization in directional localization 2 is a schematic configuration diagram illustrating an electroacoustic transducer (for example, a canal type earphone) according to a second embodiment of the present invention. The figure which shows the wiring cord connected to the earphone 40 of FIG. Circuit diagram for calculating input voltage Eout of driver unit 46L in earphone 40L for the left ear of FIG. FIG. 11 is a circuit diagram for calculating the anti-phase input voltage Eout of the driver unit 46L when the Rch audio signal SinR is added to the left earphone 40L of FIG. Frequency characteristic diagram of input voltage Eout applied to driver unit 46L in FIG. The figure which shows the frequency characteristic of the voltage (dB) of the Rch audio | voice signal SinR applied in reverse phase to the driver unit 46L of FIG. Frequency characteristic diagram of input voltage Eout applied to driver unit 46L in FIG. Frequency characteristic diagram of input voltage Eout applied to driver unit 46L in FIG. Frequency characteristic diagram showing experimental results Frequency characteristic diagram showing experimental results Frequency characteristic diagram showing experimental results Frequency characteristic diagram showing experimental results Basic acoustic equivalent circuit diagram showing a conventional earphone Frequency characteristic diagram showing a calculation example of the acoustic equivalent circuit in FIG. Circuit diagram showing a configuration example of a conventional high-frequency enhancement circuit Frequency characteristic diagram in which high-frequency enhancement circuit 10 of FIG. 25 is connected to the input side of the driver unit

  Embodiments of the present invention will become apparent from the following description of the preferred embodiments when read in light of the accompanying drawings. However, the drawings are for explanation only, and do not limit the scope of the present invention.

(Reference Example of Example 1)
FIG. 3 is a diagram illustrating stereo listening using a speaker described in Patent Document 2 or the like.
FIG. 3 shows a state in which a stereo signal is heard from the Lch speaker 20L and the Rch speaker 20R placed on the left and right front of the user 15.

A direct sound wave S20L from the Lch speaker 20L and a sound wave S20R1 slightly delayed from the right ear 15r from the Rch speaker 20R enter the left ear 151 of the user 15. Similarly, the right ear 15r of the user 15 receives a direct sound wave S20R from the Rch speaker 20R and a sound wave S20L1 from the Lch speaker 20L slightly delayed from the left ear 151. Utilizing a phenomenon called spatial crosstalk, a stereoscopic sound image space is created in stereo signal reproduction.
Here, the spatial crosstalk means that when a sound is reproduced by speaker reproduction, a sound wave S20L, which is a reproduction sound of the Lch speaker 20L, reaches the right ear 15r with a delay together with the left ear 151 and reproduces the sound of the Rch speaker 20R. The sound wave S20R, which is a sound, arrives at the left ear 151 with a delay along with the right ear 15r, and this is called crosstalk between both ears. The sound image space refers to a sound space having a direction and a distance.

FIG. 4 is a diagram for explaining the localization of a sound image for reproducing a stereo signal by a speaker.
Here, the sound image localization refers to the ability to perceive the direction and distance at which the sound was heard is called sound image localization ability, and is to determine the position of this sound image (sound having a direction and distance). In this sound image localization, a time difference between sounds heard by the left and right ears 15l and 15r is used.
In the stereo signal reproduction of FIG. 3, not only the positions of the left and right speakers 20L and 20R, but also the center (Fc), left side (Ls) and right side (Rs) of the speakers 20L and 20R as shown in FIG. Can also feel the sound images Fc, Ls and Rs.

Consider the Lch and Rch sound waves S20L, S20L1, and -20L1 at this time.
If sound waves S20L and S20R of the same level and the same phase are emitted from the Lch and Rch speakers 20L and 20R, they are the same as the sound waves from the sound image Fc on the median plane, and thus the sound image Fc on the median plane is felt. The sound wave S20L only from the Lch speaker 20L naturally has a sound image at the position of the Lch speaker 20L. Also, if the sound wave S20L1 entering the right ear 15r from the Lch speaker 20L is reproduced from the Rch speaker 20R with a sound wave S20L having an appropriate delay and the phase inverted, the sound wave S20L1 is canceled near the right ear 15r. Thus, only the sound wave S20L of the left ear 151 is perceived. Since this is the same as the sound wave (S20L) from the left sound image Ls, the left sound image Ls is felt.
The same applies to the Rch speaker 20R and the right sound image Rs.

FIG. 5 is a diagram for explaining the relationship between the localization of a sound image for stereo signal reproduction by a speaker and a signal.
From the description of FIGS. 3 and 4, as shown in FIG. 5, when the sound waves S20R and S20L of the opposite channels are applied to the Lch speaker 20L and the Rch speaker 20R at an appropriate level and in the same phase, (S20L + α1 · S20R, S20R + α2 · S20L), the sound image Fc can be localized between the Lch speaker 20L and the Rch speaker 20R. Similarly, when sound waves of the opposite channel are added to the Lch speaker 20L and the Rch speaker 20R in opposite phases after being delayed at an appropriate level (S20L-β1 · S20R, S20R-β2 · S20L), the Lch speaker 20L The sound images Ls and Rs can be localized outside the Rch speaker 20R.
From the above, it is considered that the Lch sound wave S20L also includes the in-phase component of the Rch and the delayed negative-phase component. The recording technician adjusts these ratios, delay time, phase, and frequency characteristics to create a desired reproduction sound field.

FIG. 6 is a diagram for describing the localization of a sound image in stereo signal reproduction by an earphone.
Consider the localization of a sound image when a stereo signal as shown in FIG. 6 is heard with an earphone.
In earphone listening, spatial crosstalk as shown in FIG. 3 does not occur, and there is no influence of reflection from the earlobe or the body (change in frequency characteristics). In addition, since sound waves reach the left and right ears 15l and 15r directly, there is no change in sound quality and phase when the body is moved. Therefore, the position of the sound source is determined from information such as the sound pressure difference, the phase difference, and the delay time. However, the brain is confused, and the reproduced sound field in FIG. 5 is as shown in FIG. The in-head localization like this sound image Fc is a phenomenon that is not experienced everyday and is one of the drawbacks when listening to the earphone.
Here, the in-head localization means that when music is reproduced using earphones or headphones, sound is supposed to be sounding beside the left and right ears 15l and 15r, but is reproduced in the head of the user 15. Say that you feel like. The opposite concept is out-of-head localization. The user 15 determines the distance and the direction to the sound source based on the difference in arrival time at the left and right ears 151 and 15r.

In the sound image Ls, the sound wave S20L is heard first from FIG. 4, and the sound wave -20L1 is heard later. At this time, due to the preceding sound effect, the sound source Ls is felt to the left, which is heard earlier. At that time, it is considered that the user is determined to be far away by the delay time. Therefore, the sound image Ls sounds farther than the Lch speaker 20L.
Here, the preceding sound effect refers to a phenomenon (precedence effect) in which sound images of two sound sources arriving with a time difference of several milliseconds to several tens of milliseconds are collectively perceived in the sound source direction of the sound that first arrived. This precedence effect is sometimes referred to as the Haas effect or the law of the first wavefront.

FIG. 7 is a diagram for explaining the localization of a sound image of stereo signal reproduction by an actual earphone.
In actual earphone listening, it is not always possible to hear a small group as shown in FIG. Due to the signal processing and the addition of reverberation as shown in FIG. 5, the arrangement is almost as shown in FIG. 6, but as shown in FIG.
The respective sound image areas are not separated, but overlap each other to form a reproduced sound field. In many cases, the whole is localized in the sound image Fc slightly ahead, probably because the brain approaches the everyday listening state (however, this differs depending on the model). As for the sound image Fc at the front center, the sound image Fc1 is localized at the back of the head depending on the model.

Next, with reference to FIG. 8 described in Non-Patent Document 1, a change in sound pressure at each frequency depending on the direction of the sound source in the median plane will be described.
Here, FIG. 8 is a diagram showing a change in the transmission frequency characteristic up to the ear canal entrance depending on the direction of the sound source in the median plane. The horizontal axis represents the sound source angle θ (°), and the vertical axis represents the frequency (kHz). FIG. 8 shows the change in amplitude at each frequency (kHz). 8, one speaker (sound source) 20 and the user 15 are illustrated.

  As shown in FIG. 8, when one speaker (sound source) 20 arranged on the median plane of the user 15 is moved from above the head of the user 15 to the back, the change in sound pressure of the ears 151 and 15r is represented by the frequency and When expressed by the sound source angle θ, even the sound sources 20 having the same sound pressure have different changes due to the sound source angle θ depending on the frequency. This seems to be due to the pinna shape of the ears 151 and 15r.

For example, in the frequency range of 1 kHz to 1.4 kHz, the sound pressure is higher when the sound source angle θ is 180 ° than when it is 0 °. This frequency region is easily recognized as a sound from the occipital region (180 °) of the user 15. Therefore, it is easy to localize in the back of the head.
In the frequency range of 3.5 kHz to 5 kHz, the sound pressure at the sound source angle of 0 ° is the highest, and the sound pressure at the sound source angle of 180 ° is low. This frequency region is easily recognized as a sound from the front (0 °). Therefore, it is easy to localize on the front.
In the frequency range of 7 kHz to 10 kHz, the sound pressure at the sound source angle of 60 ° to 90 ° is the highest, and the sound pressure at 0 ° and 180 ° is low. This frequency region is easily recognized as a sound from the upper front (60 °) to the overhead (90 °). Therefore, it is easy to localize upward.
Therefore, if the frequency domain 1 k-1.4 kHz is set to be low and the frequency domain 3.5 k-5 kHz is set to be high, the sound source 20 is likely to be localized in front. Also, by increasing the frequency range from 7 kHz to 10 kHz, it is considered that a sense of surround in which the high frequency range extends upward can be obtained.

Further, the direction determination band will be described with reference to FIGS. 9 and 10A and 10B described in Non-Patent Document 2.
Here, FIG. 9 is a diagram showing the front localization in the direction localization. The horizontal axis represents the center frequency (Hz), and the vertical axis represents the relative frequency (%). FIG. 10 is a diagram illustrating the rearward and upper localization in the direction localization. The upper diagram illustrates the rearward localization, and the lower diagram illustrates the upper localization. In the upper and lower diagrams of FIG. 10, the horizontal axis represents the center frequency (Hz), and the vertical axis represents the relative frequency (%).

As shown in FIG. 9, when considering the ratio of frequencies at which localization is felt forward, sound sources in the frequency range of 250 Hz to 500 Hz and the frequency range of 2.5 kHz to 4 kHz tend to be determined to be sounds coming from the front.
As shown in the upper part of FIG. 10, when considering the ratio of frequencies at which localization is felt rearward, a sound source near the frequency of 1 kHz is likely to be determined to be sound coming from the rear. If it is desired to localize the sound source forward, it is better to weaken the frequency around 1 kHz.
As shown in the lower part of FIG. 10, when considering the ratio of frequencies at which localization is felt upward, a sound source having a frequency around 8 kHz is likely to be determined to be a sound coming from above. In addition, the sound source near the frequency of 12 kHz tends to be localized in the rear. Therefore, it is considered that emphasizing the sound having a frequency of 8 kHz or more contributes to the improvement of the surround feeling.

(Configuration of Embodiment 1)
FIG. 1 is a schematic configuration diagram illustrating an electroacoustic transducer (for example, a canal earphone) according to a first embodiment of the present invention.
This canal type earphone 30 is connected to a sound source 31 via a wiring cord (not shown). The sound source 31 outputs a sound signal Sin of one of a stereo signal having a pair of left and right in-phase first audio signals (for example, Lch audio signals) and second audio signals (for example, Rch audio signals). It is composed of audio equipment and the like. The canal type earphone 30 has an input terminal 32 for inputting an audio signal Sin sent from a wiring cord (not shown) and a ground terminal 33, and a housing 34 is connected to the input terminal 32 and the ground terminal 33. Have been. An equalizer 35 and a driver unit 36 are accommodated in the housing 34, and a cylindrical sound conduit 37 constituting a sound conducting member protrudes from the front side of the housing 34. An earpiece 38 for inserting an ear hole, which constitutes a sound conducting member, is detachably mounted on the outer periphery of the sound conduit 37.

  The equalizer 35 is connected between the ground terminal 33 and the negative input terminal of the driver unit 36, and changes the frequency characteristic of the audio signal Sin in order to emphasize or reduce a specific frequency region of the audio signal Sin. This is an audio device that outputs a modified audio signal, and has, for example, an impedance Z configured by a parallel circuit of a resistor R and a capacitor C.

The driver unit 36 has a + input terminal connected to the input terminal 32, a − input terminal connected to the equalizer 35, converts the modified audio signal output from the equalizer 35 into a sound wave, and outputs the sound wave to the sound conduit 37. Things. The driver unit 36 includes, for example, a voice coil, a magnet, a diaphragm, and the like, and has an impedance Zd represented by a resistance.
The sound conduit 37 emits a sound wave output from the driver unit 36 to the earpiece 38. The earpiece 38 guides sound waves emitted from the sound conduit 37 to the ear canal, and has a substantially umbrella shape formed of an elastic member such as silicone rubber.

(Operation of Embodiment 1)
When an audio signal Sin sent from the sound source 31 via a wiring cord (not shown) is input to the input terminal 32 of the earphone 30, the frequency characteristic of the audio signal Sin is changed by the equalizer 35, and the changed audio signal is output. The output and changed sound signal is converted into a sound wave by the driver unit 36.
The equalizer 35 lowers the low-frequency reproduction sound pressure of the sound wave by the signal voltage drop Vo obtained from the following equation (1) in the low frequency region of the input audio signal Sin, and in the high frequency region of the input audio signal Sin The capacitor C eliminates the signal voltage drop Vo and relatively increases the high-frequency sound pressure of the sound wave.
Vo = R / (R + Zd) (1)

The input voltage Eout of the driver unit 36 is represented by, for example, the following equation (2), where the voltage of the audio signal Sin is Ein.
Eout = [Zd / (Zd + Z)] * Ein (2)
However,
Z = [R × (1 / (jωC)]] / [R + (1 / (jωC))]
= R / (1 + jωCR)
j; imaginary unit (= √-1)
f; frequency ω; angular frequency (= 2πf)
The sound waves converted by the driver unit 36 are emitted from the earpiece 38 to the ear canal via the sound conduit 37.

FIG. 2 is a frequency characteristic diagram of the input voltage Eout applied to the driver unit 36 of the earphone 30 in FIG. 1, in which the horizontal axis represents the frequency (Hz) and the vertical axis represents the input voltage Eout (dB).
In FIG. 2, for example,
Impedance Zd of driver unit 36 = 32Ω
The resistance R of the equalizer 35 is 22Ω.
The capacitance C of the equalizer 35 is 4.7 μF.
A waveform diagram of a calculation example of the frequency characteristics at the input voltage Eout applied to the driver unit 36 when (1) is set (the values of the internal resistance and the conductor resistance of the sound source 31 are set to 0).

  The sensitivity in the high frequency region indicated by the arrow 42 is relatively higher by 4.5 dB than the sensitivity in the low frequency region indicated by the arrow 41 in FIG. This corresponds to a state where the mass of the vibration system of the driver unit 36 is reduced to about 60%.

(Effect of Embodiment 1)
According to the first embodiment, the following effects (A) and (B) are obtained.
(A) Improvement of characteristics in relative high-frequency region For example, in a conventional electroacoustic transducer described in Patent Document 1, sound quality is improved by a housing, a driver unit, acoustic adjustment, and the like. In principle, the characteristics in the high-frequency region deteriorate. It is very difficult to improve this with a driver unit. On the other hand, according to the first embodiment, the characteristics of the high-frequency region can be easily improved, though relatively, by the values of the resistance R and the capacitance C of the equalizer 35.
That is, in the parallel circuit of the resistor R and the capacitor C constituting the equalizer 35, the sensitivity in the low frequency region is reduced, and the sensitivity in the high frequency region is relatively increased. Increasing the value of the resistor R lowers the overall sound pressure. The capacitance C weakens a decrease in sensitivity in a high-frequency region in relation to the resistance R. As the value of the capacitance C is larger, the influence of the decrease in sensitivity from the low frequency region is weakened. Since the equalizer 35 is a passive component, it does not require a power supply or the like, and can easily improve the performance (characteristics) of the conventional earphone. In particular, by merely providing the equalizer 35 constituted by a parallel circuit of the resistor R and the capacitor C, it is possible to easily improve the characteristics in a high frequency region, though relatively.

(B) Small size and low cost As shown in FIG. 2, the sensitivity in the high frequency region indicated by the arrow 42 is relatively higher than that in the low frequency region indicated by the arrow 41 by 4.5 dB. This corresponds to a state in which the mass of the vibration system of the driver unit 36 is reduced to about 60%, and it can be said that the performance of the driver unit 36 cannot be realized by the conventional improvement of the driver unit. Recently, large-capacity multilayer ceramic capacitors and the like have been developed, and the RC equalizer 35 of the first embodiment is a conventional equalizer composed of a series circuit of inductors L1, Lr and capacitors C11, C21, C1r, C2r of FIG. It is smaller and cheaper than.

(Configuration of Second Embodiment)
FIG. 11 is a schematic configuration diagram illustrating an electroacoustic transducer (for example, a pair of left and right canal earphones) according to a second embodiment of the present invention.
The pair of left and right canal-type earphones 40 includes left-ear earphones 40L and right-ear earphones 40R having the same configuration.
The pair of left and right canal type earphones 40 is an Lch audio signal of a stereo signal having a pair of left and right in-phase first audio signals (for example, Lch audio signals) SinL and second audio signals (for example, Rch audio signals) SinR. It has a first input terminal 41L for inputting SinL, a ground terminal 42LG on the Lch side, a second input terminal 41R for inputting the Rch audio signal SinR, and a ground terminal 42GR on the Rch side.

  The left ear earphone 40L has a first input terminal 41L and a ground terminal 42LG, and the housing 43L is connected to the first input terminal 41L and the ground terminal 42LG. A first equalizer 44L, a second equalizer 45L, and a driver unit 46L are housed in the housing 43L, and a cylindrical sound conduit 47L that forms a sound conducting member is protruded from the front side of the housing 46L. . On the outer periphery of the sound conduit 47L, an earpiece 48L for inserting a left ear hole, which constitutes a sound conducting member, is detachably mounted.

  The first equalizer 44L is connected between the ground terminal 42LG and a connection point NL2 connected to the negative input terminal of the driver unit 46L, and in order to emphasize or reduce a specific frequency band of the Lch audio signal SinL. Is an audio device that changes the frequency characteristic of the Lch audio signal SinL to generate a modified audio signal at the connection point NL2, and has, for example, an impedance Z1 configured by a parallel circuit of a resistor R1 and a capacitor C1. The second equalizer 45L is connected between the connection point NL2 and a connection point NR1 connected to the second input terminal 41R on the right earphone 40R side, and outputs the Rch audio signal SinR from the connection point NL2 to the driver unit. 46L is an acoustic device added in reverse phase to 46L and has, for example, an impedance Z2 constituted by a series circuit of a resistor R2 and a capacitor C2.

In the driver unit 46L, the + input terminal is connected to the first input terminal 41L via the connection point NL1, and the − input terminal is connected to the first equalizer 44L and the second equalizer 45L via the connection point NL2. The combined signal of the changed audio signal on the connection point NL2 and the Rch audio signal SinR flowing from the connection point NL2 to the driver unit 46L in the opposite phase is converted into a sound wave and output to the sound conduit 47L. The driver unit 46L includes, for example, a voice coil, a magnet, a diaphragm, and the like, and has an impedance Zd represented by a resistance.
The sound conduit 47L emits a sound wave output from the driver unit 46L to the earpiece 48L. The earpiece 48L guides sound waves emitted from the sound conduit 47L to the left ear canal, and has a substantially umbrella shape formed of an elastic member such as silicone rubber.

  The right earphone 40R has a second input terminal 41R and a ground terminal 42RG, and the housing 43R is connected to the second input terminal 41R and the ground terminal 42RG. A first equalizer 44R, a second equalizer 45R, and a driver unit 46R are accommodated in the housing 43R, and a cylindrical sound conduit 47R that constitutes a sound conducting member is protruded from the front side of the housing 46R. . An earpiece 48R for inserting a right ear hole, which constitutes a sound conducting member, is detachably attached to the outer periphery of the sound conduit 47R.

  The first equalizer 44R is connected between the ground terminal 42RG and a connection point NR2 connected to the negative input terminal of the driver unit 46R, and enhances or reduces a specific frequency band of the Rch audio signal SinR. Is an audio device that changes the frequency characteristic of the Rch audio signal SinR to generate a changed audio signal at the connection point NR2, and has, for example, an impedance Z1 configured by a parallel circuit of a resistor R1 and a capacitor C1. The second equalizer 45R is connected between the connection point NR2 and a connection point NL1 connected to the first input terminal 41L on the left earphone 40L side, and transmits the Lch audio signal SinL from the connection point NR2 to the driver unit. 46A is an acoustic device added in reverse phase to 46R, and has, for example, an impedance Z2 formed by a series circuit of a resistor R2 and a capacitor C2.

The driver unit 46R has a positive input terminal connected to the second input terminal 41R via the connection point NR1, and a negative input terminal connected to the first equalizer 44R and the second equalizer 45R via the connection point NR2. A converted sound signal on the connection point NR2, and a combined signal of the Lch sound signal SinL flowing from the connection point NR2 to the driver unit 46R in the opposite phase, are converted into sound waves and output to the sound pipe 47R. It has an impedance Zd represented by a resistance.
The sound conduit 47R emits a sound wave output from the driver unit 46R to the earpiece 48R. The earpiece 48R guides the sound waves emitted from the sound conduit 47R to the right ear hole, and has a substantially umbrella shape formed by an elastic member.

FIG. 12 is a diagram showing a three-wire type wiring cord connected to the pair of left and right canal-type earphones 40 of FIG.
In a general earphone wiring cord, three signal lines of a left (L) line / right (R) line / ground (G) line extend from a plug portion, and from a branch portion, an L line is used for Lch. For the G line and the Rch, two signal lines of the R line and the G line are used.
On the other hand, in the three-wire type wiring cord 50 of the second embodiment, a cord body 52 including three signal lines of L line / R line / G line extends from the plug part 51, and the branch part 53 The Lch side branch cord 54L consisting of three signal lines of L line / R line / G line, and the Rch side branch code 54R consisting of three signal lines of L line / R line / G line. It has become. The Lch side branch cord 54L is connected to the input side of the left ear canal type earphone 40L in FIG. 11, and the Rch side branch cord 54R is connected to the input side of the right ear canal type earphone 40R in FIG. I have.

  As described above, in the three-wire type wiring cord 50 of the second embodiment, three signal lines are required on each side as the branch cords 54L and 54R. However, manufacturing of such a three-wire wiring cord 50 is not difficult. The reason is that the conventional wiring cord uses a three-core cord even after the branch portion, but since only two necessary wires are connected, the three-wire type wiring cord 50 of the second embodiment can be easily formed. Can be manufactured.

(Overall Operation of Overall Example 2)
Of the Lch audio signal SinL and the Rch audio signal SinR sent from the wiring cord 50 in FIG. 12, the Lch audio signal SinL is input to the first input terminal 41L on the left earphone 40L side, and the Rch audio signal SinR is Is input to the second input terminal 41R of the right earphone 40R.

In the left-ear earphone 40L, the Lch audio signal SinL input to the first input terminal 41L is changed in frequency characteristics in a high-frequency region by the first equalizer 44L, and the changed audio signal is generated at the connection point NL2. Further, the Rch audio signal SinR input to the second input terminal 41R of the right earphone 40R is input to the second equalizer 45L of the left earphone 40L via the connection point NR1. The second equalizer 45L supplies the input Rch audio signal SinR from the connection point NL2 to the negative input terminal of the driver unit 46L. Then, in the driver unit 46L, the changed audio signal and the Rch audio signal SinR having the opposite phase are synthesized, and a synthesized signal is generated.
The generated synthesized signal is converted into a sound wave by the driver unit 46L on the left earphone 40L side, and is emitted from the earpiece 48L to the left ear canal via the sound conduit 47L.

Similarly, in the right ear earphone 40R, the Rch audio signal SinR input to the second input terminal 41R is changed in frequency characteristics in a high frequency region by the first equalizer 44R, and the changed audio signal is generated at the connection point NR2. Is done. Further, the Lch audio signal SinL input to the first input terminal 41L of the left earphone 40L is input to the second equalizer 45R of the right earphone 40R via the connection point NL1. The second equalizer 45R supplies the input Lch audio signal SinL from the connection point NR2 to the negative input terminal side of the driver unit 46R. Then, in the driver unit 46R, the changed audio signal and the Lch audio signal LinL having the opposite phase are synthesized to generate a synthesized signal.
The generated combined signal is converted into a sound wave by the driver unit 46R on the right earphone 40R side, and is emitted from the earpiece 48R to the right ear hole via the sound conduit 47R.

(Detailed operation of the second embodiment)
FIG. 13 is a circuit diagram for calculating the input voltage Eout of the driver unit 46L based on the Lch audio signal SinL in the left earphone 40L of FIG.
In FIG. 13, Zd is the impedance of the driver unit 46L (approximate by resistance), Z1 is the impedance of the first equalizer 44L, and Z2 is the impedance of the second equalizer 45L. The values of the internal resistance and the conductor resistance of the sound source on the Lch audio signal SinL side are set to 0. A dashed line between the ground terminal 42LG and the second input terminal 41R indicates a virtual short due to the Rch sound source impedance value = 0.
The circuit constants are, for example, as follows.
Zd = 32Ω
C1 = 4.7 μF
R1 = 22Ω
C2 = 10 μF
R2 = 33Ω

As shown in FIG. 13, an input voltage Eout of the driver unit 46L in the left earphone 40L based on the Lch audio signal SinL will be described.
As in the first embodiment, the Lch audio signal SinL has an enhancement characteristic in a high frequency region due to the impedance Z1 of the first equalizer 44L. Assuming that the impedance of the Rch audio signal source is 0, as shown in FIG. 13, the second input terminal 41R and the ground terminal 42LG are short-circuited as indicated by a broken line. Therefore, the impedance Z2 of the second equalizer 45L is connected in parallel to the first equalizer 44L. Therefore, if the voltage of the Lch audio signal SinL is expressed as Elin, and the parallel connection of the impedance Z1 of the first equalizer 44L and the impedance Z2 of the second equalizer 45L is expressed as Z1 // Z2, the input voltage Eout of the driver unit 46L is expressed by the following equation. It becomes like (3).
Eout = [Zd / (Zd + (Z1 // Z2))] * Elin (3)

FIG. 14 is a circuit diagram for calculating the anti-phase input voltage Eout to the driver unit 46L when the Rch audio signal SinR is applied to the left earphone 40L of FIG.
In FIG. 14, the input voltage Eout of the driver unit 46L in the left earphone 40L based on the Rch audio signal SinR will be described.
The Rch audio signal SinR reaches the connection point NL2 via the second equalizer 45L. Assuming that the impedance of the Lch audio signal source is 0, as shown in FIG. 14, the first input terminal 41L and the ground terminal 42LG are short-circuited as indicated by a broken line. Therefore, the impedance Z1 of the first equalizer 44L is connected in parallel to the impedance Zd of the driver unit 46L. Therefore, if the voltage of the Rch audio signal SinR is expressed as Erin, and the parallel connection of the impedance Z1 of the first equalizer 44L and the impedance Zd of the driver unit 46L is expressed as Z1 // Zd, the input voltage Eout of the driver unit 46L is expressed by the following equation (4). )become that way.
Eout = [Z1 // Zd) / (Z2 + (Z1 // Zd))] * Erin (4)
Here, even if the voltage Erin of the Rch audio signal SinR is in phase with the voltage Elin of the Lch audio signal SinL, the input voltage Eout of the driver unit 46L is applied in an opposite phase.

FIG. 15 is a frequency characteristic diagram of the input voltage Eout applied to the driver unit 46L of the left-ear earphone 40L in FIG. 13, in which the horizontal axis represents the frequency (Hz) and the vertical axis represents the input voltage Eout (dB). FIG. 15 shows the calculation result of Expression (3).
15, the waveform of the arrow 43 indicates the frequency characteristic of the input voltage Eout applied to the driver unit 46L when the Lch audio signal SinL is applied to the first input terminal 41L in FIG. Here, it is assumed that the impedance between the second input terminal 41R and the ground terminal 42LG is 0Ω with respect to the Lch audio signal SinL applied to the first input terminal 41L.

When the input voltage Eout is based on the frequency of 20 Hz, as shown by an arrow 43, the frequency of 10 kHz or more is relatively increased by 4.5 dB (that is, the sensitivity in the high frequency region is relatively increased by 4.5 dB). ). This corresponds to a state in which the mass of the vibration system of the driver unit 46L is reduced to about 60%, and it can be said that the performance of the driver unit 46L is almost impractical at present with the improvement on the driver unit side. Recently, large-capacity multilayer ceramic capacitors and the like have been developed, and the RC first equalizer 44L in FIG. 11 can be made sufficiently smaller than the LC equalizer in FIG.
That is, in the frequency characteristic of FIG. 15, as shown by the arrow 43, the high frequency region has the enhancement characteristic. This is an equalizer characteristic for sound waves localized near the Lch speaker 20L (or Rch speaker 20R) in FIG.

FIG. 16 is a diagram illustrating a frequency characteristic of a voltage (dB) of the Rch audio signal SinR applied to the driver unit 46L of the left ear canal type earphone 40L of FIG. 14 in an opposite phase. FIG. 16 shows the calculation result of Expression (4).
In FIG. 16, as indicated by an arrow 44, the middle frequency region mainly has the enhancement characteristic.

FIG. 17 is a frequency characteristic diagram of the input voltage Eout applied to the driver unit 46L of the left-ear earphone 40L in FIGS. 13 and 14, where the horizontal axis represents the frequency (Hz) and the vertical axis represents the input voltage ELout (dB). is there.
17, the waveform of the solid line indicated by the arrow 43 is the same as that of FIG. The waveform of the broken line indicated by the arrow 45 indicates the frequency characteristic of the input voltage Eout applied to the driver unit 46L when the audio signals SinL and SinR having the same phase and the same level are applied to the first and second input terminals 41L and 41R in FIG. FIG. Here, it is assumed that the impedance between the first input terminal 41L and the ground terminal 42LG is 0Ω with respect to the audio signal SinR applied to the second input terminal 41R.

That is, the waveform of the arrow 45 is a waveform obtained by combining the waveform of the arrow 43 and the waveform of the arrow 44 in FIG. 16 by (arrow 43-arrow 44). The waveform indicated by the arrow 45 indicates an equalizer characteristic for a sound wave localized in the sound image Fc at the front center in FIG. 4 in a state where the audio signals SinL and SinR of the same homology level are added to the first and second input terminals 41L and 41R. Becomes At this time, as described above, in the driver unit 46L, the audio signal SinR is added in an opposite phase to the audio signal SinL.
Although the influence on the low frequency region and the high frequency region is small, the characteristic is such that the middle frequency region is weakened. As a result, of the components localized at the front center, the middle frequency region (for example, the vocal region) is weakened.
In other words, the waveform of the arrow 45 has little effect on the low sound (mainly bass and the like) and the high sound (mainly cymbals and the like) of the sound image Fc localized at the front center, and weakens the vicinity of 1 kHz. This aims at the front localization of the sound image Fc at the front center.

FIG. 18 is a frequency characteristic diagram of the input voltage Eout applied to the driver unit 46L of the left-ear earphone 40L in FIGS. 13 and 14, where the horizontal axis represents the frequency (Hz) and the vertical axis represents the input voltage Eout (dB). is there.
In FIG. 18, the waveform of the solid line indicated by the arrow 43 is the same as that of FIG. In the waveform of the broken line indicated by the arrow 46, the frequency of the input voltage Eout applied to the driver unit 46L when the audio signals SinL and SinR having the same antiphase are applied to the first and second input terminals 41L and 41R in FIG. Properties are shown. Here, it is assumed that the impedance between the first input terminal 41L and the ground terminal 42LG is 0Ω with respect to the audio signal SinR applied to the second input terminal 41R.

That is, the waveform of the arrow 46 is a waveform of the combined characteristic when the signal of the arrow 44 in FIG. 16 is added to the characteristic of the arrow 43 by (arrow 43 + arrow 44). As described with reference to FIG. 11, the waveform of the arrow 46 has a characteristic of a component distributed in the opposite phase to the audio signal SinL and the audio signal SinR, that is, a characteristic of a component localized outside the Lch speaker 20L in FIG. 5. . At this time, as described above, in the driver unit 46L, since the audio signal SinR having the opposite phase to the audio signal SinL is added, the sound pressure is increased as shown by the waveform of the arrow 46.
Although the influence on the low frequency region and the high frequency region is small, the characteristic is such that the middle frequency region is strengthened. The same applies to the Rch-side driver unit 46R. Thereby, a feeling of spreading increases.

  As described above, according to the canal type earphone 40 of FIG. 11, the characteristics of the relative high frequency region are improved by the first equalizers 44L and 44R. Further, since the audio signals of the opposite channels are added in opposite phases by the second equalizers 45L and 45R, the level of the sound image Fc localized at the front in FIG. The level of Ls and the sound image Rs on the right side increase, and the sense of spread increases.

(Experimental result of Example 2)
In the canal type earphone 40 shown in FIG. 11, an experiment was performed using the following circuit constants, expecting a 4.5 dB enhancement in the high frequency region and a -3 dB reduction in the frontal vocals.
The circuit constants are, for example, Zd = 32Ω, R1 = 22Ω, C1 = 4.7 uF, R2 = 33Ω, and C2 = 10 uF.

FIGS. 19 to 22 are frequency characteristic diagrams showing experimental results, in which the horizontal axis represents frequency (Hz) and the vertical axis represents sound pressure level (dB).
FIGS. 19 and 20 show the effect of enhancing the high frequency region.
The solid waveform # 1L in FIG. 19 is the characteristic without the first equalizers 44L and 44R in FIG. 11, and the dashed waveform # 2L is the characteristic with the first equalizers 44L and 44R in FIG.
FIG. 20 shows a waveform # 2L- # 1L of a difference between the broken line waveform # 2L and the solid line waveform # 1L in FIG. Although the disturbance due to the measurement error can be seen in the high frequency region, the effect of enhancing the high frequency region in FIG. 15 is recognized.

21 and 22 show the effect of mixing the same phase components.
The solid line waveform # 7L in FIG. 21 is the output characteristic of the Lch side driver unit 46L when the audio signal is supplied only to the Lch side driver unit 46L in FIG. A dashed waveform # 7R is an output characteristic of the Lch-side driver unit 46L when an audio signal is simultaneously supplied to the Lch-side driver unit 46L and the Rch-side driver unit 46R in FIG.
FIG. 22 shows a waveform # 7R- # 7L of the difference between the broken line waveform # 7R and the solid line waveform # 7L of FIG. Although smaller than the calculated value, a decrease in sensitivity in the middle frequency region due to the in-phase component in FIG. 17 is recognized.

  Summarizing the above experimental results, the output characteristics due to the anti-phase component in FIG. 18 cannot be measured. However, from the experimental results in FIGS. 19 to 22, the canal type earphone 40 in FIG. 11 seems to operate as expected. It is. In the audition, it was found that the characteristics in the high frequency region were clearly improved and the sound field was spread.

(Effect of Embodiment 2)
According to the second embodiment, the following effects (a) to (c) are obtained.
(A) In the conventional electro-acoustic transducer of FIG. 25, the sound quality is improved by the housing, the driver unit, the high-frequency enhancement circuit 10, and the like, but the characteristics of the earphone in principle are reduced in the high-frequency region. It is very difficult to improve this with a driver unit as in the past. On the other hand, according to the second embodiment, since the first equalizers 44L and 44R configured by the parallel circuit of the resistor R1 and the capacitor C1 are provided, the characteristics of the high frequency region can be easily improved although relatively. . The improvement amount and improvement characteristics can be easily changed and adjusted by the values of the capacitance C1 and the resistance R1.

(B) In the conventional earphone, only the Lch audio signal is supplied to the left earphone, and only the Rch audio signal is supplied to the right earphone. On the other hand, in the second embodiment, the opposite-phase Rch audio signal is added to the left-ear earphone 40L, and the opposite-phase Lch audio signal is added to the right-ear earphone 40R. can do. The function of adjusting the sound field is not present in the related art.
(C) The adjustment amount and frequency characteristics of the sound field can be easily changed and adjusted by the values of the capacitances C1, C2 and the resistances R1, R2 of the first and second equalizers 44L, 44R, 45L, 45R. As described above, since the value can be changed and adjusted by the values of the capacitances C1 and C2 and the resistances R1 and R2, the size and cost are smaller than those of the conventional change and adjustment by the values of the inductor L and the capacitance C. Since the resistances R1 and R2 and the capacitances C1 and C2 are passive components, they do not require a power supply or the like, and the performance (characteristics) of the current model can be easily improved. In this case, a three-wire type wiring cord 50 is required, but this manufacturing is also easy.

(Modification of Examples 1 and 2)
The present invention is not limited to the first and second embodiments, and various usage forms and modifications are possible. For example, there are the following (1) to (4) as examples of this use form and modified examples.
(1) In the first embodiment, the equalizer 35 is provided in the housing 34 of the canal type earphone 30. However, the equalizer 35 may be provided outside the housing 34. Thereby, substantially the same effects as those of the first embodiment (A) and (B) can be obtained.
(2) In the second embodiment, the first and second equalizers 44L, 44R, 45L, 45R are provided in the housings 43L, 43R of the canal type earphone 40. However, the equalizers 44L, 44R, 45L, 45R are provided in the housing. It may be provided outside 43L and 43R. As a result, substantially the same effects as (a) to (c) of the second embodiment can be obtained.

(3) The canal type earphones 30, 40, 40L, and 40R of the first and second embodiments may be changed to a structure and an electric circuit other than those shown in FIGS. For example, other circuit elements and the like may be added to the equalizers 35, 44L, 44R, 45L, and 45R. Further, in the canal type earphone 40 of FIG. 11, the connection state of the first equalizers 44L, 44R and the second equalizers 45L, 45R is changed, and the second equalizers 45L, 45R are connected in series with the resistors R1, R2 and the capacitors C1, C2. Instead of the circuit, a phase inversion circuit having another circuit configuration can be provided.
(4) In addition to the canal-type earphones 30, 40, 40L, and 40R of the first and second embodiments, the present invention is also applied to other shapes of earphones such as an in-ear type earphone and an electro-acoustic transducer such as a headphone. Thus, substantially the same functions and effects as those of the first and second embodiments can be obtained.

30, 40, 40L, 40R Canal type earphone 31 Sound source 32 Input terminal 33, 42LG, 42RG Grounding terminal 34, 43L, 43R Housing 35 Equalizer 36, 46L, 46R Driver unit 37, 47L, 47R Sound conduit 38, 48L, 48R Earpiece 41L, 41R First and second input terminals 44L, 44R First equalizer 45L, 45R Second equalizer 50 Wiring code C, C1, C2 Capacitance R, R1, R2 Resistance

Claims (6)

An equalizer that receives any one of a stereo signal having a pair of left and right in-phase first audio signals and a second audio signal and changes the frequency characteristics of the audio signal to output a modified audio signal; ,
A driver unit that converts the changed voice signal into a sound wave and outputs the sound wave to a user's ear;
With
The equalizer is
Having an impedance Z constituted by a parallel circuit of a resistor R and a capacitor C,
In the low frequency region, the low-frequency reproduction sound pressure of the sound wave is reduced by the signal voltage drop Vo obtained from the following equation (1),
Vo = R / (R + Zd) (1)
Zd: impedance of the driver unit (represented by resistance)
In the high frequency region, the capacitance C eliminates the signal voltage drop Vo and relatively increases the high-frequency reproduction sound pressure of the sound wave.
An electroacoustic transducer characterized by the above. The electroacoustic transducer according to claim 1, wherein the input voltage Eout of the driver unit is represented by the following equation (2), where Ein is the voltage of the audio signal.
Eout = [Zd / (Zd + Z)] * Ein (2)
However,
Z = [R × (1 / (jωC)]] / [R + (1 / (jωC))]
= R / (1 + jωCR)
j; imaginary unit (= √-1)
f; frequency ω; angular frequency (= 2πf) The first audio signal, which is formed by a parallel circuit of a first resistor and a first capacitor, is input to the first audio signal of a stereo signal having a pair of left and right in-phase first audio signals and a second audio signal. A first equalizer that changes the frequency characteristic of the first and generates a changed audio signal;
A second equalizer configured by a series circuit of a second resistor and a second capacitor, receiving the second audio signal, and adding the second audio signal to the changed audio signal in opposite phase;
A driver unit that converts a composite signal of the changed audio signal and the second audio signal having the opposite phase to a sound wave and outputs the sound wave to a user's ear;
An electroacoustic transducer, comprising: The electroacoustic transducer according to claim 3 is
Comprising a left ear electroacoustic transducer and a right ear electroacoustic transducer,
An electroacoustic transducer characterized by the above. The left ear electro-acoustic transducer and the right ear electro-acoustic transducer are connected to a wiring cord for inputting the stereo signal.
The electroacoustic transducer according to claim 4, wherein: The electroacoustic transducer according to any one of claims 1 to 5,
Earphones or headphones,
An electroacoustic transducer characterized by the above.

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