JP2009017485A - Headphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a headphone capable of reducing noise from the outside by acoustically coupling and canceling a musical tone, a cancellation sound, and noise in an acoustic space in the headphone. <P>SOLUTION: The headphone has: a speaker unit 27 for musical tone signals driven by a musical tone signal; a microphone for detecting surrounding noise; and a speaker unit 25 for noise cancellation which is driven by a noise cancellation signal generated based on a noise signal detected by the microphone. An outside space communicates with the inside of the headphone so that the noise from the outside is acoustically coupled with the cancellation sound outputted from the speaker unit 25 for noise cancel signals in the headphone. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a headphone capable of reducing external noise.

  With the spread of portable music players, headphones for personally listening to music have also become widespread. Portable music players are often used in streets with high noise levels and in vehicles such as trains and buses, and external noises can be heard through headphones as well as music played by the players. When listening to music in the noise, the music may be drowned out by external noise, so the user tries to listen to the music by turning up the volume. May cause unpleasant feelings. In addition, even when high-quality musical sounds are reproduced by headphones, noise entering from the outside affects the musical sounds, and the quality of reproduced sounds that can be heard by the user may be reduced.

  Therefore, noise-canceling headphones that cancel out noise entering from the outside and allow only the sound to be heard by the user's ears are becoming popular. The principle of the noise-canceling headphones is that the noise entering the headphones is detected by a microphone, cancellation noise having a phase opposite to that of the detected noise signal is generated, and the noise is canceled by the cancellation noise. A typical noise-canceling headphone has one speaker and thus one voice coil. The noise signal collected by the microphone and converted into an electrical signal is passed through a filter and delay circuit to generate a noise cancellation signal with the opposite phase to the noise signal, and this noise cancellation signal and the target music signal are synthesized (added) ) And then amplifying the power to input one voice coil of the one speaker.

The sound output from the speaker is a combination of a noise cancellation signal and a musical sound signal converted into sound, and the sound converted from the noise cancellation signal cancels external noise entering the headphones and enters the user's ear. The sound is only the sound converted from the musical sound signal.
Alternatively, there is a method of synthesizing the noise cancellation signal and the tone signal immediately before the one voice coil after individually amplifying the power of the noise cancellation signal and the tone signal. However, since the two power amplifiers are connected to the voice coil in series or in parallel, there is a problem that the two power amplifiers become loads with each other.

  FIG. 4 shows an example of a conventional noise cancellation type headphone. 4, a flange member (also referred to as a baffle plate) 2 is coupled to the open end of a bottomed tubular headphone housing 1, and a head pad is disposed on the outer surface (left side in FIG. 4) of the flange member 2. 3 is fixed. When the user uses the headphones, the outer end surface of the head pad 3 hits the user's head side surface, and the user's ear 13 is positioned in the space surrounded by the head pad 3. The flange member 2 has a window hole at the center and is formed in a ring shape. A headphone unit 5 is fixed to the inner surface of the flange member 2 so as to close the window hole. The headphone unit 5 includes a flat petri dish-shaped base 6, a petri dish-shaped yoke 7 that is smaller in diameter and flatter than the base 6 fitted in the inner bottom of the base 6, and a flat flat that is fixed to the center of the inner bottom of the yoke 7. A magnet 8, a plate-shaped pole piece 9 fixed to the end face of the magnet 8, a voice coil 10 wound in a cylindrical shape, and a dome-shaped diaphragm 12 are provided.

  The open end surface of the petri dish-shaped yoke 7 and the end surface of the pole piece 9 are substantially in the same plane, and a ring-shaped gap is formed between the outer peripheral surface of the pole piece 9 and the inner peripheral surface of the open end side of the yoke 7. The voice coil 10 enters the gap. A magnetic field using the magnet 8 as a source is formed in the ring-shaped gap, and the voice coil 10 exists in this magnetic field. The diaphragm 12 is formed with an arch-shaped edge portion surrounding a dome portion at the center, and the outer periphery of the edge portion is fixed to the base 6 so that the diaphragm 12 is supported so as to vibrate in the front-rear direction. One end of the voice coil 10 is fixed to the boundary between the central dome portion and the edge portion of the diaphragm 12, and the voice coil 10 is supported so as not to contact the yoke 7 and the pole piece 9. A musical tone signal is input to the voice coil 10 from a power amplifier (driver) of an external player, the voice coil 10 is driven back and forth in accordance with each sound signal, and the diaphragm 12 vibrates accordingly, so that sound is emitted from the diaphragm 12. Be emitted. This sound reaches the user's ear 13 surrounded by the head pad 3 through the central window hole of the flange member 2.

  The above description is a description of a general headphone. In the noise canceling type headphone, a microphone for detecting ambient noise and a noise canceling signal having a phase opposite to that of the noise detected by the microphone are generated in the above configuration. A signal processing circuit such as a synthesis circuit for synthesizing (adding) the generated noise cancellation signal with the musical tone signal and inputting the resultant signal to the voice coil 10 is added. Various ideas are applied to the position of the microphone and the configuration of the signal processing circuit. In FIG. 4, M1 to M4 show various examples of arrangement positions of the noise detection microphones. M1 is an example arranged inside the headphones, and is an example arranged outside in the space immediately before the diaphragm 12. M2 to M4 are examples arranged on the outside of the headphones, M2 is an example arranged on the top of the flange member 2, M3 is arranged on the bottom of the flange member 2, and M4 is an example arranged on the outside surface of the housing 1.

  In the noise-canceling headphones, various ideas have been made to cancel external noise more effectively. For example, in the headphones described in Patent Document 1, a small cavity is provided between a diaphragm (speaker diaphragm) and the ear canal in order to reduce noise while having a relatively constant frequency response, and the diaphragm is provided in the cavity. A microphone is arranged in the vicinity of the microphone, and a feedback signal based on the output of the microphone is coupled to an input electric signal reproduced by the headphones, and the combined signal is amplified to drive the diaphragm. In the conventional example shown in FIG. 4, a microphone is arranged at a position indicated by reference numeral M1.

In Patent Document 2, in order to enhance the noise canceling effect, a synthesized sound near the outer ear is picked up by a microphone, the synthesized sound is phase-inverted, and the phase-reversed audio signal and the tone signal from the sound source are the first. An invention relating to an active noise eraser configured to add by an adder circuit, add a musical tone signal from a sound source to the addition result by a second adder circuit, amplify the addition result and output the result from the speaker to the vicinity of the ear canal is described. Has been.
The inventions described in Patent Documents 1 and 2 are also aimed at improving the performance of noise canceling headphones, but cannot achieve the object of the present invention described later. Also, the technical idea is different.

  As known inventions related to the present invention, an active noise reduction signal processing path for reducing active noise, a talk through signal processing path for providing a talk through function, an active noise reduction signal processing path, and a talk through signal processing path are provided. There has been proposed a noise reduction headset including a switching element for disabling one or both (see Patent Document 3). Referring to Patent Document 3, there is a description that the switching element disables the noise reduction signal path when the power supplied to the switching element is insufficient to operate the noise reduction signal path. . In this respect, the problem solving means is completely different from the present application, although it is related to a part of the effects of the present invention described later.

JP-A-6-343195 JP-A-9-54592 JP 2006-14307 A

  An object of the present invention is to eliminate the problems of the conventional noise canceling headphones. In other words, the conventional noise canceling headphones electrically combine the signal for canceling the noise and the tone signal and pass through the signal processing circuit, so the tone signal is affected by the noise canceling signal and the sound quality deteriorates. To do. Or, in the case of extreme, there is a problem that the sound quality difference occurs between the case where the noise canceling operation is performed and the case where the noise canceling operation is not performed, which makes the user feel uncomfortable.

  The present invention acoustically couples musical sound, cancellation sound, and external noise in the acoustic space inside the headphones, thereby eliminating noise while eliminating almost electrical coupling relationships including magnetic coupling and electrostatic coupling. The idea is to cancel. As a result, the noise cancellation signal has no effect on the tone signal, the noise cancellation signal power amplification circuit and the tone signal power amplification circuit do not become resistance to each other, and in addition, a noise cancellation type headphone with good sound quality is provided. The purpose is to do. It is another object of the present invention to provide a headphone that can listen to a reproduced sound based on a musical tone signal as in a general headphone without a noise canceling function even if a noise canceling circuit does not operate.

  The present invention relates to a musical sound speaker unit driven by a musical sound signal, a microphone for detecting ambient noise, and a noise canceling speaker unit driven by a noise cancellation signal generated based on the noise signal detected by the microphone. The external space communicates with the inside of the headphone so that the external noise and the canceling sound output from the noise canceling speaker unit are acoustically coupled inside the headphone. This is the headphones with the most important features.

  The musical sound speaker unit reproduces only musical sounds input from a sound source such as a music player. The noise canceling speaker unit receives a noise canceling signal generated based on a noise signal detected by a microphone that detects surrounding noise, and outputs a canceling sound. The noise from the outside and the canceling sound are acoustically coupled and canceled in the space inside the headphones, thereby reducing the noise from the outside.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a headphone, and reference numeral 21 denotes a headphone body. The headphone main body 21 has a housing 22, and the housing 22 has a bottomed cylindrical shape. A rear acoustic space 24 is provided at the bottom of the housing 22 (on the right side in the housing 22 in FIG. 1), and a noise canceling speaker unit 25 is fixed on the central axis of the housing 22. The front acoustic space of the noise canceling speaker unit is the front part in the housing 22 (left side in the housing 22 in FIG. 1) and the front side of the noise canceling speaker unit 25 (left side in the housing 22 in FIG. 1). 26 is provided, and a musical sound speaker unit 27 is fixed to the baffle plate 23 on the central axis of the housing 22. The musical sound speaker unit 27 has a bottomed cylindrical housing 38 integrally coupled to the baffle plate 23, and a rear acoustic space 30 is formed on the rear side of the housing 38, and hence on the rear side of the musical sound speaker unit 27. Is provided. The housing 38 partitions the front acoustic space 26 for noise cancellation on the rear side and the rear acoustic space 30 of the musical sound speaker unit 27. A front acoustic space 31 is provided in front of the musical sound speaker unit 27. A head pad 28 is attached to the baffle plate 23 so as to surround the front acoustic space 31. When the user wears the headphone main body, the outer end surface of the head pad 28 hits the head side surface of the user, and the user's ear is positioned in the front acoustic space 31.

  The baffle plate 23 is circular and has a through hole formed in the center. A plurality of through holes 33 are formed at equal intervals in the circumferential direction so as to surround the baffle plate 23, and a plurality of through holes are formed in the outer circumferential direction. Holes 34 are formed at equal intervals. On the baffle plate 23, an acoustic resistor 29 and an acoustic resistor 32 that block the back direction of the through hole 34 are affixed at positions where the back direction of the through hole 33 is blocked. An inward flange-shaped jetty 45 is formed at the rear end of the through hole at the center of the baffle plate 23 toward the center. The musical tone speaker unit 27 is configured by incorporating each member into a unit frame 39 as follows. The unit frame 39 has a circular shape, and a through hole is formed at the center. The unit frame 39 includes a cylindrical portion that extends integrally in the rear surface direction of the through hole, and includes a jetty along the outer peripheral front edge of the unit frame 39. . In the unit frame 39, a plurality of through holes 41 are formed at equal intervals in the circumferential direction so as to surround the central through hole. On the back side of the through hole 41, an acoustic resistor 43 is attached at a position to close the through hole. The unit frame 39 is fitted into the central through hole of the baffle plate 23, and the unit frame 39 is fixed to the jetty 45 facing the center direction of the baffle plate 23, and the unit frame 39 is supported by the baffle plate 23.

  The yoke 7 is fitted and fixed to the cylindrical portion of the unit frame 39. The yoke 7 constitutes a magnetic circuit together with the permanent magnet 8 and the pole piece 9. The yoke 7 has a bottomed cylindrical shape, and a flat columnar magnet 8 is installed on the inner bottom surface, and a columnar pole piece 9 is installed thereon. A circular magnetic gap is formed between the inner peripheral surface of the yoke 7 and the outer peripheral surface of the pole piece 9. The diaphragm 12 is disposed on the front side of the unit frame 39. The diaphragm 12 is circular and has a dome shape at the center, and an arch-shaped edge portion is formed in the radial direction so as to surround the diaphragm 12, and the outer periphery of the edge portion is the front outer peripheral edge portion of the unit frame 39. It is fixed to. One end of the voice coil 10 is bonded to the diaphragm 12 at the boundary between the central dome portion and the edge portion. The voice coil 10 is disposed in the magnetic gap, and is designed so that the voice coil 10 does not contact the yoke 7 and the pole piece 9 even if the voice coil 10 vibrates in the front-rear direction together with the diaphragm 12. The protector 11 has substantially the same shape as the diaphragm 12, and a plurality of holes are formed. The protector 11 covers the diaphragm 12 while maintaining a space between the diaphragm 12 and the front surface of the diaphragm 12. The outer peripheral edge of the protector 11 is bonded to the outer peripheral front edge of the unit frame 39. The outer peripheral edge of the protector 11 is pressed against the outer peripheral edge of the diaphragm 12 and adhered to the outer peripheral front edge of the unit frame 39, and the inner periphery of the jetty formed on the outer peripheral front edge of the unit frame 39 Fits on the side.

  The configuration of the noise cancellation speaker unit 25 is substantially the same as that of the musical tone speaker unit 27. The noise canceling speaker unit 25 has an outer peripheral portion fixed by an inward flange 42 extending toward the center in the vicinity of the inner bottom portion of the housing 22 so as to cover the housing 38 on the back side of the musical sound speaker unit 27. Has been. The noise canceling speaker unit 25 is configured by incorporating each member into the unit frame 40 as follows. The unit frame 40 is circular and has a through hole at the center. The unit frame 40 includes a cylindrical portion that integrally extends in the rear surface direction of the through hole. The unit frame 40 protrudes from the front outer peripheral edge of the unit frame 40 in the front direction. It has a jetty. A plurality of through holes 58 are formed in the unit frame 40 at equal intervals in the circumferential direction. On the back side of the through hole 58, an acoustic resistor 60 is attached at a position to close the through hole.

  A yoke 46 is fitted and fixed to the cylindrical portion of the unit frame 40. The yoke 46 constitutes a magnetic circuit together with the permanent magnet 48 and the pole piece 46. The yoke 46 has a bottomed cylindrical shape, and a flat columnar magnet 48 is installed on the inner bottom surface, and a columnar pole piece 50 is installed thereon. A circular magnetic gap is formed between the inner peripheral surface of the yoke 46 and the outer peripheral surface of the pole piece 50. A diaphragm 52 is disposed on the front side of the unit frame 40. The diaphragm 54 is circular and has a dome shape at the center, and an arch-shaped edge portion is formed in the radial direction so as to surround the diaphragm 54, and the outer periphery of the edge portion is the front outer peripheral edge portion of the unit frame 40. It is fixed to. One end of the voice coil 52 is bonded to the diaphragm 54 at the boundary between the central dome portion and the edge portion. The voice coil 52 is disposed in the magnetic gap, and is designed so that the voice coil 52 does not contact the yoke 46 and the pole piece 50 even when the voice coil 52 vibrates in the front-rear direction together with the diaphragm 54. The protector 56 has substantially the same shape as the diaphragm 54, and a plurality of holes are formed. The protector 56 covers the diaphragm 52 while maintaining a space between the diaphragm 52 and the front side of the diaphragm 52. The outer peripheral edge portion of the protector 56 is bonded to the outer peripheral front edge portion of the unit frame 40. The outer peripheral edge of the protector 56 is pressed against the outer peripheral edge of the diaphragm 54 and bonded to the outer peripheral front edge of the unit frame 40, and the inner periphery of the jetty formed at the outer peripheral front edge of the unit frame 40. Fits on the side.

  This headphone includes a microphone 70 that detects ambient noise. The installation position of the microphone 70 is arbitrary, and may be outside the housing 22 or the internal space of the headphones as long as the external noise can be detected. The noise signal converted into the electric signal by the microphone 70 is amplified by the amplifier 71 and is input to the voice coil 52 of the noise canceling speaker unit 25.

  A musical sound signal output from a music player (not shown) is input to an amplifier to amplify the input signal, and output after adjusting the signal level. This musical tone signal is input to the voice coil 10 of the musical tone speaker unit 27, and the diaphragm 12 is vibrated by the electromagnetic force generated by the current flowing through the voice coil 10 and the magnetic flux in the magnetic gap, thereby converting the musical tone signal into a sound wave. Is output. Since the musical tone speaker unit 27 processes only musical tone signals, for example, even if the noise canceling loudspeaker unit 25 breaks down for some reason and does not function, if the musical tone speaker unit 27 functions normally, the musical tone unit 27 can be regarded as a normal musical tone. It is possible to listen.

  On the other hand, the noise canceling speaker unit 25 operates as follows. The microphone 70 converts external noise into a noise signal, the amplifier 71 amplifies the noise signal, and adjusts the noise signal level. Further, the noise signal is input to the voice coil 52 of the noise canceling speaker unit 25 as a noise canceling signal by making the noise signal in reverse phase. The diaphragm 54 is driven by the electromagnetic force generated by the current flowing through the voice coil 25 and the magnetic flux in the magnetic gap where the voice coil 52 is disposed, and outputs a canceling sound.

  External noise passes through the acoustic resistor 32 and travels from the through hole 34 to the inside of the headphones. As described above, the noise cancellation speaker unit 25 outputs a noise cancellation sound having a phase opposite to that of the external noise. The canceling sound passes through the acoustic resistor 29 and the through hole 33 and travels into the headphones. Since the through-hole 34 through which the external noise enters and the through-hole 33 through which the cancellation sound passes are joined in the joining space 35 inside the headphones, the external noise is canceled out by the cancellation sound or the level of the external noise is reduced. The canceling sound generated by the noise canceling speaker unit 25 is in the opposite phase of the external noise. This means that the external noise that tries to enter the headphones from the through hole 34 is transmitted from the through hole 33 to the noise canceling speaker unit. 25, the external noise level that is captured in the front acoustic space 26 and reaches the inside of the headphones is canceled as a result. More specifically, the external space and the headphone interior communicate with each other in the merge space 35 so that the external noise and the cancel sound output from the noise canceling speaker unit 25 are acoustically coupled inside the headphone. The external noise is canceled out by acoustically coupled to the external noise.

  The level of the external noise that enters the headphones can be adjusted to some extent by the acoustic resistor 32. If the acoustic resistance of the acoustic resistor 32 is increased, the external noise level entering the headphones is lowered. Conversely, if the acoustic resistance of the acoustic resistor 32 is lowered, the external noise level is increased. The cancellation sound can be adjusted by adjusting the gain of the amplifier 71 that inputs a noise signal to the acoustic resistor 29 and the noise cancellation speaker unit 25. The cancellation sound can be adjusted by adjusting the acoustic resistance value of the acoustic resistor 29 in the same manner as the above-described external noise level adjustment. Further, the musical tone speaker unit 27 and the noise canceling speaker unit 25 are individually provided with amplifiers, and the amplifier 71 of the noise canceling speaker unit 25 does not have an electrical influence on the musical tone signal. Therefore, the problem that the tone quality deteriorates due to the influence of the noise cancellation signal on the musical tone signal is solved.

FIG. 2 is an equivalent circuit diagram of the acoustic space in the headphones according to the present invention. FIG. 3 is a cross-sectional view of the headphones in which the reference numerals of the equivalent circuit diagram shown in FIG. 2 are collated with the configuration of the above embodiment of the present invention. This will be described with reference to FIGS. The acoustic impedance, air stiffness, mass, etc. of each part are defined as follows.
E1 Musical sound reproduced by the loudspeaker unit 27 E2 Canceled sound generated by the noise-cancelling speaker unit P0 Sound pressure of external noise P1 Sound pressure of external noise introduced into the headphones P2 Cancellation sound introduced into the headphones Sound pressure sb stiffness of the rear acoustic chamber of the musical sound speaker unit 27 r01 acoustic resistance of the acoustic resistor 43 m01 acoustic mass of the diaphragm 12 of the musical sound speaker unit 27 s01 stiffness of the diaphragm 12 of the musical sound speaker unit 27 Ze Acoustic impedance se Stiffness of the space formed between the headphones in front of the ear r1 Acoustic resistance of the acoustic resistor 32 r2 Acoustic resistance of the acoustic resistor 29 s2 Stiffness of the rear acoustic chamber of the noise canceling speaker unit 25 m02 Noise cancellation For spin Acoustic resistance stiffness r02 acoustic resistor 60 of the vibration plate 54 of the acoustic mass s02 noise canceling loudspeaker unit 25 of the vibration plate 54 of mosquitoes unit 25

  The left half of FIG. 2 shows an equivalent circuit of the musical sound speaker unit 27, and the right half of the right half shows an equivalent circuit showing acoustic coupling between the cancel signal generated by the noise cancellation speaker unit 25 and external noise. Yes. As is clear from about half of the right side of FIG. 2, the external noise of the sound pressure P0 tries to enter the merge space 35 inside the headphones with the sound pressure P1 through the acoustic resistance 32. The cancellation sound E2 generated by the noise canceling speaker unit 25 tries to enter the merge space 35 inside the headphones with the sound pressure P2 through the acoustic resistor 29. Since the external noise and the canceling sound that try to enter the headphone are in opposite phases, the external noise is moved toward the noise canceling speaker unit 25 side by the canceling sound as indicated by arrows P1 and P2 in FIG. Will be drawn. Therefore, the external noise level is reduced by the canceling sound inside the headphones. On the other hand, the musical sound speaker unit 27 operates as an independent headphone as shown in the left half of FIG. 2 and is not electrically affected by the noise canceling speaker unit 25.

  As can be seen from the above description, according to the illustrated embodiment, the musical sound signal is not electrically influenced by the noise cancellation signal, and therefore, a musical sound faithful to the inputted musical sound signal can be reproduced. On the other hand, since the level of external noise entering the headphone is reduced by the noise canceling speaker unit 25, only musical sounds can be reproduced with high sound quality even in an environment with a high noise level.

It is a longitudinal cross-sectional view which shows the Example of the headphones concerning this invention. It is an equivalent circuit diagram of the headphones. It is a longitudinal cross-sectional view of the said Example, Comprising: The longitudinal cross-sectional view which described the code | symbol attached | subjected to the equivalent circuit schematic of FIG. It is sectional drawing which shows the example of the conventional headphones.

Explanation of symbols

8 Magnet 9 Polepiece 10 Voice coil 12 Diaphragm 23 Baffle plate 25 Noise canceling speaker unit 27 Musical sound speaker unit 29 Acoustic resistor r1 Acoustic resistance Po External noise se Acoustic space Ze Ear impedance

Claims (5)

A musical sound speaker unit driven by a musical sound signal, a microphone for detecting ambient noise, and a noise cancellation speaker unit driven by a noise cancellation signal generated based on the noise signal detected by the microphone. Headphones,
Headphones in which the external space communicates with the inside of the headphones so that the external noise and the canceling sound output from the noise canceling speaker unit are acoustically coupled inside the headphones.   The headphone according to claim 1, wherein the front acoustic space of the musical sound speaker unit and the front acoustic space of the noise canceling speaker unit communicate with the external space.   The headphone according to claim 1 or 2, wherein the noise cancellation signal for driving the noise canceling speaker unit has a phase opposite to that of the noise signal detected by the microphone.   4. The headphone according to claim 1, wherein the musical sound speaker unit is fixed to a baffle plate, and the noise cancellation speaker unit is fixed to a housing fixed to the baffle plate.   The headphone according to claim 1, further comprising an amplifier that generates a noise cancellation signal based on a noise signal detected by a microphone, wherein the gain of the amplifier is adjustable.

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