Noise Cancelling Headphones

Abstract

The present invention provides a head-mounted noise cancelling headphone that achieves a high noise reduction effect with a simple structure. The head-mounted noise cancelling headphone (1) of the present invention comprises: a head-mounted headphone unit (14); a baffle (13) for mounting the head-mounted headphone unit; an ear pad (12) mounted on the baffle; a housing (11) mounted on the baffle; a first microphone (16) for picking up external noise; a first buffer amplifier (151) for performing impedance conversion on a signal from the first microphone and outputting it; a second microphone (17) for picking up internal noise; a second buffer amplifier (152) for performing impedance conversion on a signal from the second microphone and outputting it; and a noise cancelling signal generating circuit (154) for generating a noise cancelling signal based on a synthesized signal obtained by synthesizing a signal from the first buffer amplifier and a signal from the second buffer amplifier.

Description

Technical Field

[0001] The invention relates to a head-mounted noise-cancelling headset. Background Art

[0002] The noise canceling headphone picks up so-called noise with a microphone, and cancels (cancels) the noise with a canceling sound corresponding to a canceling signal having a phase opposite to that of the picked up noise.

[0003] As one method of noise cancellation, a feed-forward method (hereinafter referred to as “FF method”) is known. FF method noise cancelling headphones collect noise outside (around) the noise cancelling headphones and generate a cancellation signal.

[0004] Here, the premise for designing the cancellation signal generating circuit and the like of the FF-type head-mounted noise cancelling headphone is that the ear pad of the head-mounted noise cancelling headphone should fit closely to the head without any gap when worn on the user's head. However, the shape of the user's head varies from person to person. Therefore, a gap may be generated between the ear pad and the head depending on the user. The FF-type head-mounted noise cancelling headphone does not assume the situation where noise enters the user's ear through the gap. Therefore, the FF-type head-mounted noise cancelling headphone cannot cancel the noise entering through the gap.

[0005] As a countermeasure to the problems existing in such FF type noise cancelling headphones, hybrid type noise cancelling headphones are known (for example, refer to Patent Document 1).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2012-23637

[0009] The hybrid noise cancelling headphone picks up the noise in the space between the ear pad and the head (front air chamber) and generates a cancellation signal. That is, the hybrid noise cancelling headphone outputs a cancellation sound corresponding to the cancellation signal generated by picking up the external noise and a cancellation sound corresponding to the cancellation signal generated by picking up the noise in the front air chamber. Accordingly, the hybrid noise cancelling headphone can achieve a higher noise reduction effect than the FF noise cancelling headphone.

[0010] However, the hybrid noise cancelling headphone requires a circuit (error correction noise reduction circuit) for generating a cancellation signal corresponding to the noise of the front air chamber in addition to a circuit for generating a cancellation signal corresponding to the external noise. Furthermore, the hybrid noise cancelling headphone requires an adder for adding the cancellation signal corresponding to the external noise and the cancellation signal corresponding to the noise of the front air chamber. Therefore, the hybrid noise cancelling headphone has a complex circuit structure and is relatively expensive. Summary of the invention

[0011] Problems to be solved by the invention

[0012] The object of the present invention is to achieve a higher noise reduction effect through a simple structure.

[0013] Technical solutions to the problem

[0014] The noise canceling headphone of the present invention is characterized by comprising: a headphone unit that outputs a sound wave corresponding to an audio signal; a baffle on which the headphone unit is mounted; an ear pad mounted on the baffle; a housing mounted on the baffle; a first microphone that picks up external noise outside the housing; a first buffer amplifier that performs impedance conversion on a signal from the first microphone and outputs the signal; a second microphone that picks up internal noise inside a front air chamber formed by the headphone unit, the baffle, the ear pad and the head of the user when the headphone is worn on the user's head; a second buffer amplifier that performs impedance conversion on a signal from the second microphone and outputs the signal; and a noise canceling signal generating circuit that generates a noise canceling signal based on a synthesized signal obtained by synthesizing a signal from the first buffer amplifier and a signal from the second buffer amplifier.

[0015] Effects of the Invention

[0016] According to the present invention, a high noise reduction effect can be achieved with a simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a perspective view showing an embodiment of the noise cancelling headphone according to the present invention.

[0018] Figure 2 It is shown Figure 1 Schematic diagram of a noise-canceling headphone worn on a user's head.

[0019] Figure 3 It is shown Figure 1 Schematic diagram of the structure of the noise reduction circuit of the head-mounted noise cancellation headphone.

[0020] Figure 4 It is shown Figure 1 A graph showing the noise reduction effectiveness of noise cancelling headphones.

[0021] Figure 5 This is a graph showing the noise canceling effect of a conventional feed-forward type noise canceling headphone.

[0022] Figure 6 1 is a schematic diagram showing the noise canceling state of a conventional feedforward type noise canceling headphone in an ideal use state.

[0023] Figure 7 The figure is a schematic diagram showing the noise canceling state of a conventional feed-forward type noise canceling headphone in actual use.

[0024] Figure 8 1 is a schematic diagram showing the noise canceling state of the noise canceling headphone of the present invention.

[0025] Fig. 9 This is a schematic diagram showing the configuration of a noise canceling circuit included in a conventional hybrid noise canceling headphone. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the noise cancelling headphone according to the present invention will be described with reference to the accompanying drawings.

[0027] Figure 1 It is a perspective view showing an embodiment of the noise cancelling headphone according to the present invention.

[0028] The noise cancelling headphone 1 is worn on the head of a user of the noise cancelling headphone 1 and outputs sound waves corresponding to an audio signal from a sound source (not shown) such as a portable music player to the ears of the user.

[0029] “User” refers to a user of the noise cancelling headphone 1 .

[0030] The headphone 1 includes a left sound emitting unit 10, a right sound emitting unit 20, and a connecting member 30. The left sound emitting unit 10 and the right sound emitting unit 20 constitute a pair of sound emitting units. The pair of sound emitting units is worn on the side of the user's head HD (see Figure 2 ) in the vicinity of the user's ear, and outputs sound waves corresponding to the audio signal from the sound source. When the head-mounted noise cancelling headphone 1 is worn on the user's head (hereinafter referred to as the "wearing state"), a front air chamber SF (refer to Figure 2 ).

[0031] The left sound emitting unit 10 is worn on the left ear LE (refer to Figure 2 ) around, and outputs sound waves corresponding to the audio signal from the sound source. The left sound unit 10 includes a housing 11, an ear pad 12, a baffle 13, and a headphone unit 14 (see Figure 2 ).

[0032] The housing 11 is mounted on the baffle 13 and contains the headphone unit 14 and the like. The housing 11 is cup-shaped. The housing 11 is made of a synthetic resin such as ABS (Acrylonitrile-Butadiene-Styrene) resin. The housing 11 has a sound pickup hole 11h. The sound pickup hole 11h connects the outside and the inside of the housing 11 (the rear air chamber SR described later (see Figure 2)). The sound pickup hole 11h is the first sound pickup hole in the present invention.

[0033] The ear pad 12 is attached to the baffle 13 and functions as a buffer between the baffle 13 and the side of the head HD. The ear pad 12 is in an oval ring shape. The ear pad 12 abuts against the side of the head HD of the user. The ear pad 12 is made of an elastic material such as polyurethane foam that is easily deformable.

[0034] The baffle 13 holds the headphone unit 14. The baffle 13 separates the front air chamber SF from the rear air chamber SR. The baffle 13 has a sound pickup hole 13h (see Figure 2 The sound pickup hole 13h communicates with the front air chamber SF and the rear air chamber SR. The sound pickup hole 13h is the second sound pickup hole in the present invention.

[0035] The right sound unit 20 is worn around the right ear in the side of the user's head HD, and outputs sound waves corresponding to the audio signal from the sound source. The right sound unit 20 includes a housing 21, an ear pad 22, and a baffle 23. The functions and structures of the housing 21, the ear pad 22, and the baffle 23 are the same as the functions and structures of the housing 11, the ear pad 12, and the baffle 13. Therefore, a detailed description of the structure of the right sound unit 20 is omitted.

[0036] The connecting member 30 connects the left sound unit 10 and the right sound unit 20, respectively, and supports the left sound unit 10 and the right sound unit 20, respectively. The connecting member 30 fixes the head-mounted noise cancelling headphone 1 to the user's head. When the head-mounted noise cancelling headphone 1 is worn, the connecting member 30 applies lateral pressure to the left and right sound units 10 and 20 toward the side of the user's head HD, and fixes the left and right sound units 10 and 20 to the side of the user's head HD.

[0037] Figure 2 1 is a schematic diagram showing a state (wearing state) in which the noise cancelling headphone 1 is worn on the head (side of the head) of the user.

[0038] For ease of explanation, the figure schematically shows the side of the head HD and the left ear LE.

[0039] This figure shows that a front air chamber SF is formed between the noise canceling headphone 1 and the side of the head HD. In addition, this figure shows that the front air chamber SF and the rear air chamber SR are divided by the baffle 13.

[0040] The “front air chamber SF” refers to the acoustic space (space formed by the headphone unit 14, baffle 13, ear pad 12, and side head HD) enclosed by the user's head (side head HD) and the noise cancelling headphone 1 when the headphone 1 is worn.

[0041] The “rear air chamber SR” refers to an acoustic space enclosed by the housing 11 , the baffle 13 , and the headphone unit 14 (a space formed by the housing 11 , the baffle 13 , and the headphone unit 14 ).

[0042] also, Figure 2 It is shown that a part of the ear pad 12 does not abut against the side of the head HD. That is, the figure shows that there is a gap between a part of the ear pad 12 and the side of the head HD. The front air chamber SF communicates with the outside of the noise cancelling headphone 1 through the gap.

[0043] Here, generally, the shape of the side of the head HD of a person varies from person to person, so a gap is easily generated between the side of the head HD and the ear pad 12. When a gap is generated between the ear pad 12 and the side of the head HD, the sound insulation of the noise cancelling headphone 1 is reduced, and the external noise of the noise cancelling headphone 1 (hereinafter referred to as "external noise") enters the interior of the front air chamber SF (acoustic space) through the gap.

[0044] As shown in the figure, the noise cancelling headphone 1 includes a headphone unit 14 , a substrate 15 , a first microphone 16 , and a second microphone 17 inside a housing 11 (a rear air chamber SR).

[0045] The headphone unit 14 converts an audio signal from a sound source into a sound wave corresponding to the audio signal and outputs the sound wave. The headphone unit 14 is attached to the baffle 13.

[0046] The substrate 15 is used for mounting a noise reduction circuit (hereinafter referred to as "NC circuit"). The details of the NC circuit will be described later.

[0047] The first microphone 16 collects external noise outside the housing 11 and generates a noise signal corresponding to the external noise. The first microphone 16 is, for example, a condenser microphone.

[0048] "External noise" refers to audio from a sound source other than a portable music player or the like, for example, audio reaching the inside of the housing 11 (rear air chamber SR) and the front air chamber SF from the outside of the noise canceling headphone 1. In other words, "external noise" refers to so-called noise.

[0049] The first microphone 16 is mounted on the housing 11. The first microphone 16 is arranged in a position away from the headphone unit 14 and close to the sound pickup hole 11h in the rear air chamber SR. The sound pickup portion of the first microphone 16 is exposed to the outside of the housing 11 through the sound pickup hole 11h. The first microphone 16 picks up external noise through the sound pickup hole 11h. The first microphone 16 is connected to the NC circuit mounted on the substrate 15 through the signal line L1.

[0050] It should be noted that the structure in which the sound pickup portion of the first microphone is exposed to the outside is not limited to the structure exposed through the sound pickup hole (sound pickup hole 11h). That is, for example, the sound pickup portion (sound pickup surface) of the first microphone may be arranged inside the sound pickup hole in a manner connected to the outer surface of the housing.

[0051] The second microphone 17 collects the noise inside the front air chamber SF (hereinafter referred to as "internal noise") at a position close to the ear of the user and generates a noise signal corresponding to the internal noise. The second microphone 17 is, for example, a condenser microphone.

[0052] “Internal noise” refers to external noise that enters the interior of the front air chamber SF through a gap between the ear pad 12 and the side of the head HD or through the ear pad 12 .

[0053] The second microphone 17 is mounted on the baffle 13. The second microphone 17 is arranged at a position in the rear air chamber SR that does not overlap with the ear pad 12 and the headphone unit 14. The sound pickup portion of the second microphone 17 is exposed to the front air chamber SF through the sound pickup hole 13h. The second microphone 17 picks up internal noise through the sound pickup hole 13h. The second microphone 17 is connected to the NC circuit mounted on the substrate 15 through the signal line L2.

[0054] It should be noted that the structure in which the sound pickup portion of the second microphone is exposed to the front air chamber is not limited to the structure in which it is exposed through the sound pickup hole (the sound pickup hole 13h). That is, for example, the sound pickup portion (the sound pickup surface) of the second microphone may be arranged inside the sound pickup hole in a manner that is connected to a side surface on the front air chamber side of the baffle.

[0055] In addition, the second microphone can also be arranged inside the front air chamber as long as it can pick up the internal noise.

[0056] Figure 3 1 is a schematic diagram showing a configuration of an NC circuit included in the noise cancelling headphone 1 .

[0057] The NC circuit includes a first buffer amplifier 151 , a second buffer amplifier 152 , a microphone signal amplifier 153 , a noise canceling signal generating circuit 154 , a noise canceling signal amplifier 155 , a musical sound input terminal 156 , and a musical sound signal amplifier 157 .

[0058] The first buffer amplifier 151 performs impedance conversion on the noise signal from the first microphone 16. The first buffer amplifier 151 outputs the noise signal after the impedance conversion to the microphone signal amplifier 153.

[0059] The second buffer amplifier 152 performs impedance conversion on the noise signal from the second microphone 17. The second buffer amplifier 152 outputs the noise signal after the impedance conversion to the microphone signal amplifier 153.

[0060] The microphone signal amplifier 153 amplifies a signal (hereinafter referred to as a "composite signal") including an output signal from the first buffer amplifier 151 (a noise signal corresponding to external noise) and an output signal from the second buffer amplifier 152 (a noise signal corresponding to internal noise). The microphone signal amplifier 153 outputs the amplified composite signal to a noise cancellation signal generating circuit (hereinafter referred to as an "NC signal generating circuit") 154.

[0061] The NC signal generating circuit 154 generates a noise cancellation signal based on the output signal from the microphone signal amplifier 153 (the synthesized signal amplified by the microphone signal amplifier 153). That is, the NC signal generating circuit 154 generates a noise cancellation signal including a noise cancellation signal based on the external noise picked up by the first microphone 16 (the noise cancellation signal based on the signal from the first buffer amplifier 151) and a noise cancellation signal based on the internal noise picked up by the second microphone 17 (the noise cancellation signal based on the signal from the second buffer amplifier 152). In other words, the noise cancellation signal generated by the NC signal generating circuit 154 includes a noise cancellation signal having a phase opposite to that of the external noise and a noise cancellation signal having a phase opposite to that of the internal noise. The NC signal generating circuit 154 outputs the noise cancellation signal to the noise cancellation signal amplifier (hereinafter referred to as "NC signal amplifier") 155.

[0062] Here, the noise canceling signal having an opposite phase to the external noise is a signal for canceling the external noise, and the noise canceling signal having an opposite phase to the internal noise is a signal for canceling the internal noise.

[0063] The noise canceling signal having a phase opposite to that of the external noise is the first noise canceling signal in the present invention, and the noise canceling signal having a phase opposite to that of the internal noise is the second noise canceling signal in the present invention.

[0064] The NC signal amplifier 155 amplifies the noise canceling signal (first noise canceling signal, second noise canceling signal) from the NC signal generating circuit 154. An output unit (not shown) of the NC signal amplifier 155 is connected to an input unit (not shown) of the headphone unit 14.

[0065] An audio signal (musical sound) from a sound source such as a portable music player is input to the musical sound input terminal 156 . The musical sound input terminal 156 outputs the audio signal to the musical sound signal amplifier 157 .

[0066] The musical sound signal amplifier 157 amplifies the audio signal from the musical sound input terminal 156. An output unit (not shown) of the musical sound signal amplifier 157 is connected to another input unit (not shown) of the headphone unit 14.

[0067] As described above, the headphone unit 14 converts the audio signal from the sound source into a sound wave (a sound wave corresponding to the audio signal) and outputs it, and converts it into a sound wave corresponding to the first noise canceling signal and a sound wave corresponding to the second noise canceling signal and outputs them. That is, the headphone unit 14 outputs a sound wave corresponding to the musical sound signal and a sound wave corresponding to the noise canceling signal amplified by the NC signal amplifier 155.

[0068] It should be noted that the second buffer amplifier may also be an impedance conversion unit of the second microphone. That is, for example, the second microphone includes a microphone unit that converts internal noise into a noise signal and an impedance conversion unit that performs impedance conversion on the noise signal and outputs it. The impedance conversion unit of the second microphone functions as the second buffer amplifier. According to this structure, the number of parts constituting the NC circuit is reduced.

[0069] Figure 4 : is a graph showing the noise cancelling effect of the noise cancelling headphone 1 .

[0070] The figure shows the frequency characteristics when the noise canceling function of the headphone 1 is turned off (thin line) and turned on (bold line). In the figure, the solid line shows the frequency characteristics of the left sound unit 10, and the dotted line shows the frequency characteristics of the right sound unit 20.

[0071] As shown in the figure, the noise cancelling headphone 1 exhibits a noise cancelling effect of attenuating the gain by about 8 dB to 30 dB, particularly in the low frequency band (around 30 Hz to 500 Hz).

[0072] Figure 5 This is a graph showing the noise canceling effect of a conventional FF type noise canceling headphone.

[0073] This figure shows the frequency characteristics of the existing FF-type headphone when the noise canceling function is turned off (thin line) and when the function is turned on (thick line). In the figure, the solid line shows the frequency characteristics of the left sound unit, and the dotted line shows the frequency characteristics of the right sound unit.

[0074] As shown in the figure, the existing FF-type head-mounted noise cancelling headphones have a noise cancelling effect of about 6dB to 24dB gain reduction in the low frequency band (around 80Hz to 400Hz). However, compared with the head-mounted noise cancelling headphones 1, the noise cancelling effect of the existing FF-type head-mounted noise cancelling headphones appears in a narrower frequency band and the gain reduction is smaller. In other words, compared with the existing FF-type head-mounted noise cancelling headphones, the head-mounted noise cancelling headphones 1 have a greater noise cancelling effect in a wider frequency band.

[0075] Here, the principle of why the noise cancelling headphone of the present invention can achieve a higher noise cancelling effect than the conventional FF type noise cancelling headphone will be described.

[0076] Figure 6 1 is a schematic diagram showing the noise canceling state of a conventional FF type noise canceling headphone in an ideal use state.

[0077] Figure 7 FIG. 1 is a schematic diagram showing the noise canceling state of a conventional FF type noise canceling headphone in actual use.

[0078] By wearing the noise cancelling headphones on the user's head, the so-called passive effect occurs, that is, the noise in the high-frequency band (high-frequency components) is muffled (eliminated) by the shielding of the ear pads. That is, in an ideal use state (hereinafter referred to as the "ideal state"), by wearing the noise cancelling headphones on the user's head, the high-frequency components are muffled (eliminated) by the ear pads, and the high-frequency components will not reach the front air chamber. On the other hand, the low-frequency band noise (low-frequency components) of the external noise cannot obtain a sufficient passive effect, and will reach the front air chamber in a state where the volume is reduced. That is, in headphones that do not have a noise reduction function, the passive effect is weak. The noise cancellation signal generating circuit (NC signal generating circuit) of the existing FF-type noise cancelling headphones plays a role in eliminating the low-frequency components of the external noise that reaches the front air chamber due to the weak passive effect. The existing noise cancellation signal generating circuit performs signal processing on the picked up external noise that takes into account the amount of volume reduction caused by the passive effect in the ideal state, generates a noise signal, and generates a noise cancellation signal with a phase opposite to the generated noise signal. As Figure 6 As shown, the low-frequency external noise (N1) is eliminated by the generated noise elimination signal (C1). As a result, the external noise is eliminated to a predetermined noise elimination level (L1).

[0079] However, the premise for designing the existing noise cancellation signal generating circuit (NC signal generating circuit) under an ideal state is the passive effect under an ideal state (a state in which the front air chamber is sealed) in which the user's head (side head) and the ear pad fit closely together without a gap. The existing noise cancellation signal generating circuit under an ideal state generates a cancellation signal based on a reference characteristic based on this premise. That is, when a gap is generated between the user's head (side head) and the ear pad and the passive effect as in the premise is not generated, the existing noise cancellation signal generating circuit generates a cancellation signal (C1) based on the external noise (N1) when the passive effect is obtained according to the reference characteristic. As a result, Figure 7As shown, part of the low-frequency external noise (L2) will not be eliminated by the generated cancellation signal (C1) and will remain in the front air chamber. In other words, part of the external noise will not be eliminated, and the user cannot fully obtain the effect of the head-mounted noise cancellation headphones. It should be noted that Figure 7 In the figure, N2 represents the external noise that actually reaches the front air chamber.

[0080] Figure 8 1 is a schematic diagram showing the noise canceling state of the noise canceling headphone of the present invention.

[0081] The noise canceling headphone of the present invention uses the second microphone to Figure 7 In the actual use state shown, a part of the low-frequency external noise (L2) that cannot be eliminated by the existing FF-type head-mounted noise canceling headphone and remains is picked up as internal noise, and a noise cancellation signal (C2) having a phase opposite to that of the picked-up internal noise is generated. As a result, the noise that cannot be completely eliminated by the existing FF-type head-mounted noise canceling headphone and remains as internal noise in the actual use state is canceled to a predetermined cancellation level (L1).

[0082] As described above, the noise cancelling headphone of the present invention generates a cancellation signal corresponding to the external noise picked up by the first microphone, and also generates a cancellation signal corresponding to the internal noise picked up by the second microphone. As a result, the noise cancelling headphone of the present invention can achieve a higher noise cancelling effect than the existing FF type noise cancelling headphone.

[0083] Fig. 9 This is a schematic diagram showing the configuration of an NC circuit included in a conventional hybrid noise cancelling headphone.

[0084] The front air chamber SFA and the rear air chamber SRA shown in the figure are Figure 3 The space corresponding to the front air chamber SF and the rear air chamber SR shown.

[0085] The NC circuit of the existing hybrid noise canceling headphone (hereinafter referred to as "existing NC circuit") includes a microphone signal amplifier 153A, an NC signal generating circuit 154A, an NC signal amplifier 155A, a musical sound input terminal 156A, a musical sound signal amplifier 157A, an error correction NC circuit 18A, and an adder 19A. Figure 3 Compared with the NC circuit included in the noise cancelling headphone 1 shown in the figure, an error correction NC circuit 18A and an adder 19A are included.

[0086] The functions and structures of the musical sound input terminal 156A, the musical sound signal amplifier 157A, the first microphone 16A, and the second microphone 17A shown in the figure are similar to those of the Figure 3The musical sound input terminal 156, musical sound signal amplifier 157, first microphone 16, and second microphone 17 have the same functions and configurations. Therefore, detailed descriptions of the musical sound input terminal 156A, musical sound signal amplifier 157A, first microphone 16A, and second microphone 17A are omitted.

[0087] The microphone signal amplifier 153A amplifies the noise signal from the first microphone 16A.

[0088] The NC signal generating circuit 154A generates a noise canceling signal based on the output signal from the microphone signal amplifier 153A. The NC signal generating circuit 154A generates a noise canceling signal having a phase opposite to that of the external noise picked up by the first microphone 16A. The NC signal generating circuit 154A outputs the noise canceling signal to the NC signal amplifier 155A via the adder 19A. For details about the adder 19A and the NC signal amplifier 155A, see the following description.

[0089] The error correction NC circuit 18A generates an error correction signal, which is used to cancel noise that cannot be completely canceled by the cancellation signal corresponding to the noise signal from the first microphone 16A (hereinafter referred to as "error noise"). The second microphone 17A picks up the error noise, generates a noise signal corresponding to the error signal, and outputs it to the error correction NC circuit 18A. The error correction NC circuit 18A outputs the error correction signal to the adder 19A.

[0090] The adder 19A adds the noise cancellation signal from the NC signal generation circuit 154A and the error correction signal from the error correction NC circuit 18A. The adder 19A outputs the added signal to the NC signal amplifier 155A.

[0091] The NC signal amplifier 155A amplifies the added signal (noise cancellation signal and error correction signal) generated by the addition by the adder 19A. An output unit (not shown) of the NC signal amplifier 155A is connected to an input unit (not shown) of the headphone unit 14A.

[0092] like Fig. 9 As shown, the NC circuit included in the conventional hybrid type noise cancelling headphone includes a second microphone 17A, an error correction NC circuit 18A, and an adder 19A in addition to the NC circuit included in the conventional FF type noise cancelling headphone.

[0093] On the other hand, the NC circuit (see Figure 3) In addition to the NC circuit of the existing FF type headphone, the second microphone 17 and the second buffer amplifier 152 are included. That is, the second microphone 17 and the second buffer amplifier 152 function as a filter for canceling the noise from the gap between the user's head (side of the head) and the ear pad. In addition, the second microphone 17 and the second buffer amplifier 152 automatically correct the noise cancellation signal for the user's unique noise caused by the individual difference in the gap between the user's head (side of the head) and the ear pad.

[0094] It should be noted that, as mentioned above, the second buffer amplifier may also be an impedance conversion unit provided by the second microphone. In this case, the NC circuit provided by the noise cancelling headphone of the present invention is simply formed by adding a second microphone to the NC circuit provided by the existing FF type noise cancelling headphone. That is, the noise cancelling headphone of the present invention can reduce the signal processing corresponding to the noise signal, and achieve the same noise reduction effect as the existing hybrid type through a simple NC circuit.

[0095] According to the above-described embodiments, the NC circuit of the noise cancelling headphone of the present invention does not need to have a relatively expensive error correction NC circuit and a complicated adder as the NC circuit of the existing hybrid noise cancelling headphone. That is, the NC circuit of the noise cancelling headphone of the present invention has a simpler structure than the NC circuit of the existing hybrid noise cancelling headphone. On the other hand, the noise cancelling headphone of the present invention can achieve a higher noise cancelling effect than the existing FF noise cancelling headphone. As described above, the noise cancelling headphone of the present invention can achieve a higher noise cancelling effect with a simple structure.

[0096] Description of Reference Numerals

[0097] 1: Noise-canceling headphones

[0098] 10: Left sound unit

[0099] 11: Shell

[0100] 11h: Sound pickup hole (1st sound pickup hole)

[0101] 12: Ear pads

[0102] 13: Baffle

[0103] 13h: Sound pickup hole (second sound pickup hole)

[0104] 14: Headphone unit

[0105] 15: Substrate

[0106] 151: 1st buffer amplifier

[0107] 152: Second buffer amplifier

[0108] 153: Microphone signal amplifier

[0109] 154: Noise cancellation signal generating circuit (NC signal generating circuit)

[0110] 155: Noise elimination signal amplifier (NC signal amplifier)

[0111] 156: Music input terminal

[0112] 157: Music signal amplifier

[0113] 16: Microphone No. 1

[0114] 17: Second Microphone

[0115] 20: Right sound unit

[0116] 21: Shell

[0117] 22: Ear pads

[0118] 23: Baffle

[0119] 30: Connecting parts

[0120] SF: Front air chamber

[0121] SR: Rear air chamber.

Claims

1. A head-mounted noise cancelling headset, It is characterized in that have: A headphone unit that outputs sound waves corresponding to the audio signal; a baffle for mounting the headphone unit; ear pads mounted on the baffle; a housing mounted on the baffle; a first microphone for picking up external noise outside the housing; a first buffer amplifier that performs impedance conversion on a signal from the first microphone and outputs the signal; a second microphone for picking up internal noise inside a front air chamber formed by the headphone unit, the baffle, the ear pad, and the head of the user when the headphone is worn on the head of the user; a second buffer amplifier that performs impedance conversion on a signal from the second microphone and outputs the signal; a noise canceling signal generating circuit for generating a noise canceling signal based on a synthesized signal obtained by synthesizing a signal from the first buffer amplifier section and a signal from the second buffer amplifier section; as well as a microphone signal amplifier that amplifies the synthesized signal, The noise cancellation signal generation circuit generates the noise cancellation signal based on the synthesized signal amplified by the microphone signal amplifier.

2. The noise cancelling headphone according to claim 1, It is characterized in that The noise cancellation signal comprises: A first noise cancellation signal having a phase opposite to that of the external noise; and A second noise cancellation signal having a phase opposite to that of the internal noise.

3. The noise cancelling headphone according to claim 1, It is characterized in that The second buffer amplifier is an impedance conversion unit included in the second microphone.

4. The noise cancelling headphone according to claim 1, It is characterized in that The first microphone is arranged inside a rear air chamber formed by the headphone unit, the baffle, and the housing.

5. The noise cancelling headphone according to claim 1, It is characterized in that The first microphone is mounted on the housing. A sound pickup portion of the first microphone is exposed to the outside of the housing.

6. The noise cancelling headphone according to claim 1, It is characterized in that The second microphone is mounted on the baffle. A sound pickup portion of the second microphone is exposed to the front air chamber.

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