JPH08275281A - Noise cancellation headphone - Google Patents

Abstract

PURPOSE: To attain noise cancellation up to a high frequency by providing a microphone coaxially to a notched part in the center of a protector of the driver unit so as to be opposite to the driver unit. CONSTITUTION: A driver unit 19 is provided with a frame 25 and a diaphragm 26 is arranged in the frame 25. A cylindrical bobbin 27 is fitted to the center of the diaphragm 26. Furthermore, a voice coil 28 is wound on the bobbin 27, a protector 30 is fitted so that the voice coil 28 faces an outer circumferential part of a magnet 29 and a notched part 31 is provided to the center of the protector 30 and the noise detection microphone 18 is fitted to the missing part 31. The noise detection microphone 18 is coupled coaxially with the driver unit 19 through the fitting as above. Then, the driver unit 19 generates a signal tone cancelling the noise to cancel noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise-canceling headphone, and in particular, it comprises an acoustic tube having an inner diameter substantially the same as that of the ear canal, detects external noise by a noise detecting microphone, and cancels the signal by a driver unit. The present invention relates to a noise-canceling headphone that is supplied to a computer to cancel external noise.

[0002]

2. Description of the Related Art FIG. 9 shows a feedback type noise canceling headphone using a conventional non-reflective headphone. This headphone is provided with a substantially straight acoustic tube 1, and a driver unit 2 and a noise detection microphone 3 are attached to predetermined portions on the outer peripheral side of the acoustic tube 1, respectively. A portion of the acoustic tube 1 to which the earpiece 4 is attached serves as a mounting portion to the auricle, and an end portion on the opposite side of the acoustic tube 1 is a non-reflection end filled with the sound absorbing material 5.

The detection microphone 3 detects an external noise and supplies a detection signal to the equalizer 6, and the equalizer 6 generates a signal for canceling the noise.
The noise is canceled in this driver unit 3 after being amplified by and supplied to the driver unit 3.

As described above, in the conventional noise canceling headphone of the feedback type using the non-reflective headphone, the noise detecting microphone 3 is arranged between the driver unit 2 for generating the noise for canceling the noise and the ear. It was This is due to the layout restrictions of the driver unit 2 and the microphone 3 on the acoustic tube 1.

[0005]

When the driver unit 2 and the noise detection microphone 3 are arranged apart from each other in this manner, there are two adverse effects. The first problem is the driver unit 2 for the noise detection microphone 3.
The signal emitted from the nearest end and the farthest end of the signal causes a dip in which the signal is canceled in the vicinity of a relatively high frequency, for example, 20 kHz, as shown in FIG. There was a problem.

The second problem is that the delay period due to the distance from the driver unit 2 to the detection microphone 3 has a large amount of phase rotation at a relatively high frequency. That is, as shown in FIG. 10, the phase was completely inverted at 6 Hz, and the effect of noise cancellation was reduced.

Due to the above two reasons, there is a problem that the feedback type noise canceling control cannot be performed up to a relatively high frequency, and the canceling amount of external noise and the canceling band are limited.

The present invention has been made in view of the above problems. In particular, it is possible to prevent the occurrence of dips on the high frequency side and to perform feedback type noise cancellation up to a relatively high frequency. It is an object of the present invention to provide a noise canceling headphone.

[0009]

According to the present invention, the inner diameter of the ear canal is substantially the same as that of the ear canal, and the one end side is a pinna mounting portion and the other end side is a substantially non-reflective end for sound. An acoustic tube is provided, and a driver unit is attached to the coupling hole of the acoustic tube so that the diaphragm faces the inside of the acoustic tube, and a microphone for detecting external noise is coaxially mounted on the driver unit. Place and
Moreover, the noise canceling signal circuit forms a noise canceling signal having a phase opposite to the external noise detected by the microphone and supplies this signal to the triber unit.

The acoustic tube may be curved so as to surround the outer peripheral portion of the microphone unit. Further, when the acoustic tube is curved, a connecting hole is formed in an arc shape in the curved portion, and the diaphragm of the driver unit is attached so as to communicate with the inside of the acoustic tube at the part of the connecting hole. do it.

In the structure in which the microphone is mounted on the driver unit substantially coaxially with the driver unit, the central portion of the protector of the driver unit is omitted, and the microphone is coaxial so as to face the driver unit at the missing portion. It should be attached to.

[0012]

External noise is detected by the microphone arranged on the driver unit substantially coaxially with the driver unit. Then, a noise canceling signal having a phase opposite to that of the external noise is formed by the noise canceling signal forming circuit, and this noise canceling signal is supplied to the driver unit, and the driver unit produces a signal sound for canceling noise. Generate and cancel noise.

[0013]

1 to 5 show a noise canceling headphone according to an embodiment of the present invention, which is equipped with an acoustic tube 11. As shown in FIGS. 1 and 2, the acoustic tube 11 is composed of a cylindrical tube, the middle portion of which is curved, and an earpiece 12 is attached to one end of the acoustic tube 11. The portion to which the earpiece 12 is attached is shown in FIG. As shown in FIG. 7, the ear canal 34 is attached to the entrance of the external auditory meatus 35. In addition, the eardrum 36 is located at the back of the external auditory meatus 35. On the other hand, the acoustic tube 12
A sound absorbing material 13 is filled into the other end of the sound source so that the sound absorbing member 13 serves as a substantially non-reflective end of sound.

A coupling hole 17 is formed in the curved portion of the acoustic tube 11 so as to extend substantially in the axial direction, and a noise detecting microphone 18 is located inside the curved portion of the acoustic tube 11. Is installed.
The driver unit 19 is attached to the side of the acoustic tube 11 coaxially with the microphone 18. That is, the vibration plate (diaphragm) of the driver unit 19 faces the inside of the acoustic tube 11 through the coupling hole 17.

The output end of the noise detecting microphone 18 is connected to an equalizer 20 as shown in FIG. 3, and the equalizer 20 is connected to an amplifier 21.

FIG. 4 shows the internal structure of the driver unit 19. The driver unit 19 includes a frame 25, and a diaphragm 26 is arranged in the frame 25. And diaphragm 2
A cylindrical bobbin 27 is attached to the center of 6. A voice coil 28 is wound around the bobbin 27, and the voice coil 28 is arranged so as to face the outer peripheral portion of the magnet 29. Then, the protector 30 is attached so as to cover the upper surface of the diaphragm 26, and the central portion of the protector 30 is omitted so that the notch 3
The noise detection microphone 18 can be attached to the missing portion 31. By such attachment, the noise detection microphone 18 is coaxially coupled to the driver unit 19.

As described above, in the noise canceling headphone of this embodiment, the acoustic tube 11 having an inner diameter substantially the same as the diameter of the ear canal 35 is connected to the ear canal 35 while keeping the earpiece 12 hermetically sealed. And acoustic tube 11
Headphone driver unit 1 at the middle position in the length direction of
In order to increase the area of connection with the driver 9, it is curved to match the unit 19 and is connected to the driver unit 19.

The end of the acoustic tube 11 opposite to the one end attached to the ear is filled with the sound absorbing material 13 to form non-reflective headphones. Further, as shown in FIG. 4, a hole 3 is formed in the protector 30 in the center of the headphone driver unit 19.
1 is opened and the microphone 18 is coupled coaxially with the diaphragm 26 while being brought close to the diaphragm 26.

Next, the operating principle of the noise-canceling headphone having such a structure will be described with reference to FIGS. 3 and 5. The external noise signal P _N detected by the noise detection microphone 18 is supplied to a headphone driver unit 19 through an amplifier 21 via an equalizer circuit 20 for realizing appropriate noise cancellation by a feedback control circuit, and this driver unit 19 Is outputting a cancel signal.

FIG. 5 is a block diagram showing this operation.
Is. The external noise P _N will be reduced by the feedback loop as represented by the following equation. That is, the noise is reduced by the gain of the denominator in the following equation.

[Equation 1] A major feature of this embodiment is the configuration of the acoustic circuit shown in FIG. FIG. 4 shows the configuration of the headphone driver unit 19, which includes the diaphragm 26 and the microphone 1.
And 8 are coaxially opposed to each other. This eliminates the drawback that the phase rotation becomes faster due to the dip point (see FIG. 10) that is generated on the transfer function from the headphone to the microphone because it is not conventionally arranged coaxially. That is, conventionally, the phase was 6 kHz at -180 ° as shown in FIG.

However, in this embodiment, as shown in FIG. 6, there is no dip point and the phase is -180.
The frequency at which the angle becomes ° has risen to 7 kHz. The reason is that the microphone 18 according to the present embodiment and the diaphragm 26 of the driver unit 19 are coaxially arranged. Microphone 18 if both are not coaxial
As seen from the above, the difference in the transmission distance of the sound waves from the farthest portion and the closest portion of the diaphragm 26 becomes large, resulting in a dip. However, as in the present embodiment, the microphone 18 is replaced by the diaphragm 26 of the driver unit 19.
By arranging them coaxially with each other, the sound wave transmission distances from all the circumferential surfaces of the diaphragm 26 when viewed from the microphone 18 become substantially equal, and the dip is eliminated.

Further, the microphone 18 is attached to the lacking portion 31 of the protector 30 of the driver unit 19,
Microphone 1 as close as possible to diaphragm 26
By arranging 8, the distance between the diaphragm 26 and the microphone 18 was shortened, and the phase of 6 kHz in the past was increased to 9 kHz at -180 ° (see FIG. 7). For these two major reasons, the effect of noise cancellation is b, c in FIG.
It changes like. Note that the characteristic indicated by a in FIG. 8 is the characteristic of the conventional noise canceling headphones.

When the microphone and the diaphragm are not coaxially arranged, the cancel band is 30H.
Peak value of cancellation amount is 16 dB at z to 1.2 kHz
Is. By arranging the microphone 18 and the diaphragm 26 coaxially with each other, the cancellation band becomes 22 Hz to 3.1 kHz and the peak value of the cancellation amount is improved to 23 dB as shown by b in FIG. Further, by bringing the microphone 18 as close as possible to the diaphragm 26, the cancellation band reaches 20 Hz to 3 kHz and the peak value of the cancellation amount reaches 30 dB, as shown in FIG.

By thus disposing the microphone unit 18 for detecting external noise coaxially with the driver unit 19 for emitting a signal sound for canceling the external noise, and as close as possible to the diaphragm 26 of the driver unit 19. By reducing the phase rotation of the characteristics of the feedback type noise canceling loop, the canceling amount and the cancelable band are expanded as a result.

Therefore, it is possible to realize a more comfortable environment even under a louder noise than before, and it is possible to cancel noise in a high frequency range which could not be realized by the conventional noise-cancellation type headphones. .

Further, since the stability of the noise canceling loop is improved, a safe noise canceller which hardly oscillates can be realized. Further, since the phase rotation of the acoustic circuit is reduced, the number of stages of the electrical equalizer circuit can be reduced, and thus the cost of the signal forming circuit can be reduced.

[0027]

INDUSTRIAL APPLICABILITY As described above, the present invention has the same inner diameter as the external auditory meatus, one end of which is a mounting portion for the auricle, and the other end of which is a substantially non-reflective end of sound. A driver unit is attached to the coupling hole of the acoustic tube so that the diaphragm faces the inside of the tube, and a microphone for detecting noise is arranged on the driver unit almost coaxially with the driver unit. A noise canceling signal having a phase opposite to that of the external noise detected by the noise canceling signal forming circuit is formed, and this noise canceling signal is supplied to the driver unit to cancel the noise.

Accordingly, by disposing the microphone for detecting the external noise substantially coaxially with the driver unit on the driver unit, the distance between the microphone and all the positions in the circumferential direction of the diaphragm of the driver unit. Are equal to each other, and it is possible to prevent the occurrence of dip on the high frequency side. In addition, it becomes possible to shorten the distance between the microphone and the driver unit, and the frequency at which the phase becomes -180 ° shifts to the high frequency side, and feedback type noise cancellation is performed up to a higher frequency. Will be possible.

According to the configuration in which the acoustic tube is curved so as to surround the outer peripheral portion of the microphone unit, the coupling area between the driver unit and the acoustic tube becomes large. In addition, by forming a coupling hole in an arc shape in the curved portion of the acoustic tube and mounting the driver unit so that it communicates with the inside of the acoustic tube at the location of this coupling hole, the large coupling hole allows the inside of the acoustic tube to enter. The driver unit can be attached to the acoustic tube so that the diaphragm faces.

According to the structure in which the central portion of the protector of the driver unit is omitted and the microphone is coaxially attached so as to face the driver unit at this missing portion, the noise detecting microphone and the driver unit are separated from each other. It becomes possible to make the distance closer, and it is possible to perform noise cancellation more reliably up to a higher frequency.

[Brief description of drawings]

FIG. 1 is an external perspective view of noise canceling headphones.

FIG. 2 is a cross-sectional view of essential parts in a state where the noise canceling headphones are worn on the ears.

FIG. 3 is a block diagram showing a feedback loop of noise canceling headphones.

FIG. 4 is a cross-sectional view of a driver unit.

FIG. 5 is a block diagram showing transmission of external noise.

FIG. 6 is a graph showing a transfer function when a microphone and a diaphragm are coaxially arranged.

FIG. 7 is a graph showing a transfer function from the headphone to the microphone when the microphone and the diaphragm are coaxial and are brought close to each other.

FIG. 8 is a graph showing cancellation characteristics.

FIG. 9 is a sectional view of a main part of a conventional noise canceling headphone.

FIG. 10 is a graph of a transfer function showing the same transfer characteristic.

[Explanation of symbols]

 11 Acoustic Tube 12 Earpiece 13 Sound Absorbing Material 17 Coupling Hole 18 Noise Detection Microphone 19 Driver Unit 20 Equalizer 21 Amplifier 25 Frame 26 Diaphragm 27 Bobbin 28 Voice Coil 29 Magnet 30 Protector 31 Absent 34 Auricle 35 External Ear Canal 36

Claims (4)

[Claims] 1. An acoustic tube having an inner diameter substantially the same as that of the external auditory meatus, one end side being a mounting portion for the auricle, and the other end side being a substantially non-reflecting end of sound, and the inside of the acoustic tube. A driver unit attached to the coupling hole portion of the acoustic tube so that the diaphragm faces, and a microphone that is arranged on the driver unit substantially coaxially with the driver unit and that detects external noise, A noise canceling headphone, comprising: a noise canceling signal forming circuit that forms a noise canceling signal that has a phase opposite to the external noise detected by the microphone and is supplied to the driver unit. 2. The noise canceling headphone according to claim 1, wherein the acoustic tube is curved so as to surround an outer peripheral portion of the microphone unit. 3. The connecting hole is formed in an arc shape in a curved portion of the acoustic tube, and the driver unit is attached so as to communicate with the inside of the acoustic tube at a portion of the connecting hole. The noise-canceling headphones according to claim 2. 4. The center of the protector of the driver unit is omitted, and the microphone is coaxially mounted so as to face the driver unit at the missing portion. The noise-canceling headphones described.