Noise-canceling earphone, and noise cancellation method for earphone

Abstract

Disclosed in the present application is a noise-canceling earphone, comprising a sound production apparatus, which comprises a cavity, an electroacoustic transducer, a first microphone, a second microphone and a signal processing unit, wherein the electroacoustic transducer partitions the cavity into a first cavity and a second cavity, a first sound output hole is formed in the first cavity, and a second sound output hole is formed in the second cavity; the first microphone collects a sound signal from the first cavity and converts same into an electrical signal; the second microphone collects a sound signal from the second cavity and converts same into an electrical signal; the signal processing unit comprises a first signal processing circuit, a second signal processing circuit and a first adder; the two signal processing circuits perform signal processing on the two electrical signals, so as to obtain two electrical signals having the same amplitude and opposite phases; and after the first adder processes the two electrical signal, no signal is transmitted to the electroacoustic transducer. The present application improves the noise cancellation performance, without generating howling, and when a user uses open earphones but does not want to hear sounds from the outside world, an excellent immersive experience is provided.

Description

Noise-cancelling headphones and headphone noise-cancelling method

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on June 30, 2023, with application number 202310793898.1 and application name “A Noise Cancelling Headphone and Noise Cancelling Method Thereof”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to a sound-generating device, and more specifically, to a noise-canceling headphone and a headphone noise-canceling method. Background Art

[0003] In the related art, in the feedforward noise reduction system of in-ear or semi-in-ear noise reduction headphones, the second microphone or the second microphone pickup hole is kept as far away as possible from the sound emitted by the electroacoustic transducer, such as the electroacoustic transducer emitting sound energy through the first sound outlet, or the second sound outlet, or the tuning hole of the audio device, to avoid the occurrence of howling. Since the sound of such headphones enters the human ear canal through the sound outlet, the ability to radiate sound outward is relatively small. The second microphone can be kept away from the tuning hole or the sound outlet on the headphones to avoid the occurrence of howling. However, for the feedforward noise reduction system of open audio devices, the second microphone can easily pick up the sound emitted by the first sound outlet and the second sound outlet, thereby forming a positive feedback system in the partial frequency band of 10Hz-20000Hz, causing howling.

[0004] Summary of the Invention

[0005] The purpose of this application is to provide a noise reduction headset and a headset noise reduction method to solve the problem of excessive howling sound in current headsets.

[0006] In a first aspect, the present application discloses a noise-canceling headset, the noise-canceling headset comprising a sound-generating device, the sound-generating device comprising: a cavity, an electroacoustic transducer, a first microphone, a second microphone, and a signal processing unit;

[0007] The electroacoustic transducer is arranged in the cavity, dividing the cavity into a first cavity and a second cavity, the first cavity is provided with a first sound outlet hole, and the second cavity is provided with a second sound outlet hole;

[0008] The first microphone is disposed in the first cavity and is used to collect the sound signal of the electroacoustic transducer in the first cavity and convert it into an electrical signal S1;

[0009] The second microphone is close to the second sound outlet, and is used to collect the sound signal of the electroacoustic transducer in the second cavity and convert it into an electrical signal S2;

[0010] The signal processing unit includes a first signal processing circuit, a second signal processing circuit and a first adder. The first signal processing circuit is used to perform signal processing on the electrical signal S1, and the processed electrical signal is S11. The second signal processing circuit is used to perform signal processing on the electrical signal S2, and the processed electrical signal is S12. The electrical signal S11 and the electrical signal S12 have equal amplitudes and opposite phases. The first adder is used to process the electrical signal S11 and the electrical signal S12, and the processed electrical signal is S3. The electrical signal S3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit, and the amplitude of the electrical signal S3 is zero.

[0011] In a second aspect, the present application discloses a headphone noise reduction method, which is applied to a noise-canceling headphone, wherein the noise-canceling headphone includes an electroacoustic transducer, a first microphone, a second microphone, and a signal processing unit, wherein the signal processing unit includes a first signal processing circuit, a second signal processing circuit, and a first adder, wherein the first microphone is used to collect a sound signal of the electroacoustic transducer in a first cavity and convert it into an electrical signal S1, and the second microphone is used to collect a sound signal of the electroacoustic transducer in a second cavity and convert it into an electrical signal S2. The method comprises the following steps:

[0012] The first microphone collects the sound signal of the electroacoustic transducer in the first cavity and converts it into an electrical signal S1;

[0013] The second microphone collects the sound signal of the electroacoustic transducer in the second cavity and converts it into an electrical signal S2;

[0014] The first signal processing circuit processes the electrical signal S1, and the processed electrical signal is S11. The second signal processing circuit processes the electrical signal S2, and the processed electrical signal is S12. The electrical signals S11 and S12 have equal amplitudes and opposite phases.

[0015] The first adder processes the electrical signal S11 and the electrical signal S12. The processed electrical signal is S3. The electrical signal S3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit. The amplitude of the electrical signal S3 is zero.

[0016] In combination with the above technical solution, in the present application, the first adder is used to process the electric signal S11 and the electric signal S12, and the processed electric signal is S3. The electric signal S3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit, and the amplitude of the electric signal S3 is zero. In this solution, the signal processing unit is provided with a processing circuit. When the external sound wave signal is equivalent to 0, this situation can be approximately obtained in the anechoic chamber. The electric signal S1 and the electric signal S2 are adjusted to be completely equal in amplitude and completely opposite in phase through the first processing circuit and the second processing circuit. After the two signals are added, the signal transmitted to the outside is zero. At this time, in the noise reduction system, the sound signals of the electroacoustic transducer received by the first microphone 13 and the second microphone 14 will be offset in the noise reduction circuit and will not be transmitted back to the electroacoustic transducer, thereby avoiding the microphone receiving the sound of the electroacoustic transducer to generate an electric signal, and the electric signal is transmitted back to the electroacoustic transducer, generating a cycle in which the sound signal is transmitted to the microphone, thereby avoiding howling. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG1 is a schematic diagram of the overall structure of a first embodiment of the noise-cancelling earphones of the present application;

[0018] FIG2 is a schematic diagram of wearing the first embodiment of the noise-canceling headphones of the present application;

[0019] FIG3 is a schematic diagram of the circuit structure of the first embodiment of the noise-cancelling headphones of the present application;

[0020] FIG4 is a schematic diagram of a circuit structure of a fourth embodiment of the noise-canceling headphones of the present application;

[0021] FIG5 is a schematic diagram of a circuit structure of a fifth embodiment of the noise-canceling headphones of the present application;

[0022] FIG6 is a schematic diagram of a circuit structure of a sixth embodiment of the noise-canceling headphones of the present application;

[0023] FIG7 is another circuit structure diagram of the sixth embodiment of the noise-canceling earphones of the present application;

[0024] FIG8 is a schematic diagram of the circuit structure of another noise-canceling headphone of the present application;

[0025] FIG9 is a schematic diagram of a circuit structure of an eighth embodiment of a noise-canceling headphone according to the present application;

[0026] FIG10 is a schematic diagram of a circuit structure of a ninth embodiment of a noise-canceling headphone according to the present application;

[0027] FIG11 is a circuit diagram of a tenth embodiment of a noise-canceling headphone according to the present application;

[0028] FIG12 is another circuit structure diagram of the tenth embodiment of a noise-canceling headphone according to the present application;

[0029] FIG13 is a structural diagram of another noise-canceling headphone according to an eleventh embodiment of the present application;

[0030] Figure 14 is a schematic diagram of the principle structure of a dipole sound source;

[0031] Figure 15 is a schematic diagram of the principle structure of a quadrupole sound source;

[0032] FIG16 is a schematic diagram showing a transfer function-amplitude-frequency comparison of another noise-cancelling headphone of the present application without the first tuning hole;

[0033] FIG17 is a schematic diagram showing a transfer function-amplitude-frequency comparison of another noise-cancelling headphone of the present application when the first tuning hole or the acoustic short-circuit tube is provided;

[0034] FIG18 is a schematic diagram of the resonant frequency formed by the first cavity and the first sound outlet;

[0035] FIG19 is a schematic structural diagram of another noise-canceling headphone according to the present invention;

[0036] FIG20 is a flow chart of a first embodiment of the headphone noise reduction method of the present application;

[0037] Figure 21 is a schematic diagram of the ear structure;

[0038] FIG22 shows the relative position relationship between the headwind and the noise-canceling headphones;

[0039] FIG23 shows the relative position relationship between the headwind and the noise-canceling headphones at another angle. DETAILED DESCRIPTION

[0040] In the embodiments of this application, the term "and / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0041] In the embodiments of the present application, the term "plurality" refers to two or more than two, and other quantifiers are similar.

[0042] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0043] This application discloses a noise-canceling headphone. Referring to Figures 1 to 3 , the noise-canceling headphone of this embodiment includes a sound-generating device 10, which comprises a cavity, an electroacoustic transducer, a first microphone 13, a second microphone 14, and a signal processing unit. The electroacoustic transducer divides the cavity into a first cavity and a second cavity, with a first sound outlet 11 and a second sound outlet 12, respectively, provided in the first cavity and the second cavity. Specifically, the electroacoustic transducer is provided with a diaphragm, which vibrates back and forth, squeezing the air in the first and second cavities, generating sound, which is then transmitted through the first sound outlet 11 and the second sound outlet 12, respectively. Due to the structure of the noise-canceling headphone, when the diaphragm vibrates, the sound emitted from the first sound outlet 11 and the second sound outlet 12 has substantially the same amplitude and substantially opposite phase. The reason why the two sets of sounds are not identical in amplitude and phase is due to the different acoustic impedances before and after the electroacoustic transducer diaphragm.

[0044] The first microphone 13 is disposed in the first cavity, and is used to collect the sound signal of the electroacoustic transducer in the first cavity and convert the sound signal into an electrical signal S1.

[0045] The second microphone 14 is close to the second sound outlet 12 and is used to collect the sound signal of the electroacoustic transducer in the second cavity and convert the sound signal into an electrical signal S2.

[0046] Please refer to Figure 3. The signal processing unit includes a first signal processing circuit, a second signal processing circuit and a first adder. The first signal processing circuit is used to process the electrical signal S1, and the processed electrical signal is S11. The second signal processing circuit is used to process the electrical signal S2, and the processed electrical signal is S12. The electrical signals S11 and S12 have equal amplitudes and opposite phases.

[0047] The first adder is used to process the electric signal S11 and the electric signal S12. The processed electric signal is S3. The electric signal S3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit. The amplitude of the electric signal S3 is zero. In this solution, the signal processing unit is provided with a processing circuit. When the external sound wave signal is equivalent to 0, this situation can be approximately obtained in an anechoic chamber. The electric signal S1 and the electric signal S2 are adjusted to be completely equal in amplitude and completely opposite in phase through the first processing circuit and the second processing circuit. After the two signals are added, the signal transmitted to the outside is zero. At this time, in the noise reduction system, the sound signals of the electroacoustic transducer received by the first microphone 13 and the second microphone 14 will be offset in the noise reduction circuit and will not be transmitted back to the electroacoustic transducer, thereby avoiding the microphone receiving the sound of the electroacoustic transducer to generate an electric signal, and the electric signal is transmitted back to the electroacoustic transducer, generating a cycle in which the sound signal is transmitted to the microphone, thereby avoiding howling.

[0048] As an implementation scheme, in this embodiment, the first signal processing circuit includes a first gain adjuster and a first filter electrically connected, and the second signal processing circuit includes a second gain adjuster and a second filter electrically connected. The parameters of the first gain adjuster are Gain1, the parameters of the first filter are Filter1, the parameters of the second gain adjuster are Gain2, and the parameters of the second filter are Filter2. The electrical signal S11 = S1*Gain1*Filter1, the electrical signal S12 = S2*Gain2*Filter2, and the electrical signal S3 satisfies:

[0049] S3=S1*Gain1*Filter1+S2*Gain2*Filter2=0.

[0050] After the above conditions are met, the parameters of the first signal processing circuit and the second signal processing circuit are kept unchanged. In this embodiment, the first gain adjuster and the first filter, the second gain adjuster and the second filter keep the set parameters unchanged so that the electrical signal S3 meets the above conditions.

[0051] In this embodiment, the order in which the first gain adjuster and the first filter process the electrical signal S1 is not limited, that is, the first gain adjuster can first process the electrical signal S1, and then the first filter can process the electrical signal processed by the first gain adjuster. The order can also be the opposite, that is, the first filter can first process the electrical signal S1, and then the first gain adjuster can process the electrical signal processed by the first filter. Similarly, it applies to the second gain adjuster and the second filter. In some schemes, the first gain adjuster and the first filter are integrated into one regulator, and the regulator can include the functions of the first gain adjuster and the first filter, or the regulator can perform signal regulation on the electrical signal S1 or S2 to meet the above requirements, which also falls within the protection scope of this scheme. Similarly, it applies to the second gain adjuster and the second filter.

[0052] As an implementation scheme, in this embodiment, the center distance between the sound pickup hole of the first microphone 13 and the first sound output hole 11 can be set to be no greater than 5 mm according to actual conditions.

[0053] The center distance between the sound pickup hole of the second microphone 14 and the second sound output hole 12 may also be set to no more than 5 mm according to actual conditions.

[0054] When designing traditional noise-canceling headphones, the sound pickup hole of the second microphone 14 is placed as far away from the sound outlet as possible, that is, the microphone is prevented from collecting the sound emitted by the electroacoustic transducer and only collects external noise. In many noise-canceling headphones, the second microphone 14 is even designed at the acoustic zero point of the acoustic dipole radiation sound field formed by the first sound outlet 11 and the second sound outlet 12, so that the second microphone 14 cannot collect the sound emitted by the electroacoustic transducer at all. These designs will cause the noise reduction system to judge the noise inaccurately, fail to achieve a better noise reduction effect, or cause howling. This solution has a different technical approach from the above solution. This solution is to place the first microphone 13 as close to the first sound outlet 11 as possible and the second microphone 14 as close to the second sound outlet 12 as possible. For example, the center distance between the sound pickup hole of the first microphone 13 and the first sound outlet 11 can be set to no more than 5mm according to actual conditions. The center distance between the sound pickup hole of the second microphone 14 and the second sound outlet 12 can also be set to no more than 5mm according to actual conditions. It is convenient for the first microphone 13 to collect the sound of the first sound outlet 11, and the second microphone 14 to collect the sound of the second sound outlet 12. It can be seen from the above scheme that in this embodiment, by setting up an anti-howling circuit, the sound signal collected by the first microphone 13 and the sound signal collected by the second microphone 14 will be completely offset in the noise reduction system and will not be transmitted back to the electroacoustic transducer. Compared with those schemes in which the microphone is designed to be far away from the sound outlet, this scheme has better noise reduction and anti-howling effects.

[0055] In this embodiment, the electrical signals S1 and S2 are processed to obtain electrical signals S11 and S12 having equal amplitudes and opposite phases, and then the electrical signals S11 and S12 are processed by a first adder to achieve zero signal transmission to the electroacoustic transducer, thereby preventing the generation of howling.

[0056] Based on the first embodiment shown in Figures 1 to 3, a second embodiment of the noise-canceling headphones of the present application is proposed. The difference between this embodiment and the first embodiment is that in this embodiment, the first microphone 13 is also used to collect external sound signals and convert the external sound signals into electrical signals N1. The second microphone 14 is also used to collect external sound signals and convert the external sound signals into electrical signals N2. The first signal processing circuit is also used to process electrical signal N1, and the processed electrical signal is N11. The second signal processing circuit is also used to process electrical signal N2, and the processed electrical signal is N12. The first adder is also used to process electrical signals N11 and N12, and the processed electrical signal is N3. Electrical signal N3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit. That is, the second embodiment is for wearing noise-canceling headphones under normal circumstances. Among them, electrical signal N3 satisfies the following: N3 = N1*Gain1*Filter1 + N2*Gain2*Filter2.

[0057] When the noise-cancelling earphones are in a normal working state, the signal marking the first signal processing circuit is S1N, and the signal marking the second signal processing circuit is S2N.

[0058] When the noise-canceling headphones are working normally, before the first adder, the signals of the first signal processing circuit and the second signal processing circuit are respectively:

[0059] S1N=S1*Gain1*Filter1+N1*Gain1*Filter1;

[0060] S2N=S2*Gain2*Filter2+N2*Gain2*Filter2;

[0061] In this embodiment, the signal N3 of the third signal path is first calculated based on the signal S1N of the first signal path and the signal S2N of the second signal path.

[0062] After passing through the first adder, since S11 and S12 have the same amplitude and opposite phase, the signal of the electroacoustic transducer is completely cancelled out, and only the external sound wave remains. Therefore, the signal N3 of the third signal path can be expressed as:

[0063] N3=N1*Gain1*Filter1+N2*Gain2*Filter2.

[0064] Then, the external sound wave signal N2 collected by the second microphone 14 is calculated based on the signal N3 of the third signal path:

[0065] N2=(N3-N1*Gain1*Filter1)) / Gain2*Filter2.

[0066] The electrical signal N3 transmitted at this time is not necessarily consistent with the target noise reduction signal, but it can also play a role in preventing howling.

[0067] The noise signal in the target area (the space between the first sound outlet 11 and the eardrum) is N0. This signal can be obtained by using a sensor near the target area or by multiplying the external signal N1 collected by the first microphone 13 by a specific function. Alternatively, in some implementations, the external signal N1 collected by the first microphone 13 is used to effectively replace N0. The characteristic function of the electroacoustic conversion of the electroacoustic transducer is G(s).

[0068] Specifically, please refer to Figure 4. As an implementation plan of Example 4, the signal processing unit also includes a third signal processing circuit, which processes the electrical signals S3 and N3 processed by the first adder. The processed electrical signal is S4. The electrical signal S4 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit. The electroacoustic transducer is also used to generate a noise reduction signal based on the received electrical signal.

[0069] The third signal processing circuit includes a fourth gain adjuster and a fourth filter electrically connected to each other, a parameter of the fourth gain adjuster is Gain4, and a parameter of the fourth filter is Filter4.

[0070] The characteristic function of the electroacoustic conversion of the electroacoustic transducer is G(s). After receiving the electrical signal S4, the noise reduction signal generated is S4*G(s).

[0071] To achieve the noise reduction effect, it is necessary to satisfy S4*G(s)+N0=0, where S4=(S3+N3)*Gain4*Filter4, where S3=0, and N3=N1*Gain1*Filter1+N2*Gain2*Filter2. This is used to determine the specific parameters of the fourth gain adjuster Gain4 and the fourth filter Filter4. When the parameters of Gain4 are determined, Filter4=-N0 / ((N3+S3)*Gain4)*G(s)).

[0072] Please refer to Figure 5, as an implementation plan of Example 5, the signal processing unit also includes a fourth signal processing circuit and a second adder. The fourth signal processing circuit is used to process the electrical signal S1 and the electrical signal N1, and the processed electrical signal is S5. The second adder is used to process the electrical signal S3, the electrical signal N3 and the electrical signal S5, and the processed electrical signal is S6. The electrical signal S6 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit. The electroacoustic transducer is also used to generate a noise reduction electrical signal based on the received electrical signal.

[0073] The fourth signal processing circuit includes a third gain adjuster and a third filter electrically connected to each other, a parameter of the third gain adjuster is Gain3, and a parameter of the third filter is Filter3.

[0074] The characteristic function of the electroacoustic conversion of the electroacoustic transducer is G(s). After receiving the electrical signal S6, the generated noise reduction signal is S6*G(s).

[0075] In order to achieve the effect of noise reduction, it is necessary to satisfy S6*G(s)+N0=0, S6*G(s)=-N0, where

[0076] S6=(S1+N1)*Gain3*Filter3+S3+N3,

[0077] Where S3 = 0, N3 = N1 * Gain1 * Filter1 + N2 * Gain2 * Filter2, and this is used to determine the specific parameters of the third gain adjuster Gain3 and the fourth filter parameter Filter3. Once the parameters of Gain3 are determined, Filter3 = (-N0 / G(s) - N3) / (S1 + N1) * Gain3.

[0078] Please refer to Figure 6, as an implementation plan of Example 6, the signal processing unit also includes a third signal processing circuit, a fourth signal processing circuit and a second adder. The fourth signal processing circuit is used to process the electrical signal S1 and the electrical signal N1, and the processed electrical signal is S7. The third signal processing circuit is used to process the electrical signal S3 and the electrical signal N3, and the processed electrical signal is S8. The second adder is used to process the electrical signal S7 and the electrical signal S8, and the processed electrical signal is S9. The electrical signal S9 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit, and the electroacoustic transducer is also used to generate a noise reduction sound signal based on the noise reduction electrical signal.

[0079] The third signal processing circuit includes a fourth gain adjuster and a fourth filter electrically connected, wherein the parameter of the fourth gain adjuster is Gain4 and the parameter of the fourth filter is Filter4. The fourth signal processing circuit includes a third gain adjuster and a third filter electrically connected, wherein the parameter of the third gain adjuster is Gain3 and the parameter of the third filter is Filter3.

[0080] The characteristic function of the electroacoustic conversion of the electroacoustic transducer is G(s). After receiving the electrical signal S9, the noise reduction signal generated is S9*G(s).

[0081] In order to achieve the noise reduction effect, it is necessary to satisfy S9*G(s)+N0=0, S9*G(s)=-N0, where S9=S7+S8, S7=(S1+N1)*Gain3*Filter3, S8=(S3+N3)*Gain4*Filter4.

[0082] With reference to the solutions of the fourth, fifth and sixth embodiments, it can be seen that when the target noise signal N0 is the same, S4=S6=S9.

[0083] In the fourth embodiment, S4=(S3+N3)*Gain4*Filter4;

[0084] In the fifth embodiment, S6=(S1+N1)*Gain3*Filter3+S3+N3;

[0085] In the sixth embodiment, S9=(S1+N1)*Gain3*Filter3+(S3+N3)*Gain4*Filter4

[0086] It can be seen from this that in the solution of Example 6, the parameters of Gain4 and Filter4 are different from those in Example 4, and the parameters of Gain3 and Filter3 are different from those in Example 5, that is, the electrical signal S7 is not equal to S5, and the electrical signal S8 is not equal to S4. In Example 6, the parameters of Gain4, Filter4, Gain3 and Filter3 need to be reset to achieve the purpose of eliminating the target noise signal N0.

[0087] Among them, the noise reduction scheme of embodiment 4 is partially identical to the existing feedforward noise reduction scheme, the noise reduction scheme of embodiment 5 is partially identical to the existing feedback noise reduction scheme, and embodiment 6 is partially identical to the existing hybrid noise reduction scheme including feedforward noise reduction and feedback noise reduction. However, due to the structure of the noise reduction headphones of this scheme, which is equivalent to having two electroacoustic transducers, and the second microphone 14 receives the sound signal of the electroacoustic transducer, it is more difficult to process the noise reduction than the existing noise reduction technology. However, the above three embodiments, combined with the anti-howling scheme of embodiment 1, can not only solve the noise reduction problem of open headphones, but also solve the problem of howling that is easily generated in the existing noise reduction process. It should be noted that the noise reduction effect of embodiment 6 is better than the noise reduction effects of embodiments 4 and 5.

[0088] Referring to FIG7 , based on the first embodiment shown in FIG1 to FIG3 , and the fourth, fifth, and sixth embodiments shown in FIG4 to FIG6 , a further embodiment of the present application is proposed. In this embodiment, the noise-canceling headphones further include a power amplifier, which is used to amplify the output signal of the signal processing unit before the electroacoustic transducer. The amplification factor of the power amplifier is K. In the fourth embodiment, S4*G(s)*K+N0=0;

[0089] In the fifth embodiment, S6*G(s)*K+N0=0; in the sixth embodiment, S9*G(s)*K+N0=0. In different embodiments, the value of K may vary according to requirements, wherein K may be greater than 1 or less than 1.

[0090] After the electroacoustic transducer obtains the output signal of the signal processing unit according to the noise reduction system, it generates a noise reduction signal according to the signal, and generates noise reduction sound according to the noise reduction signal to offset the noise in the target area.

[0091] Furthermore, the noise-canceling headphones can be configured as ear-hook headphones, which structurally include an ear hook and a battery unit. One end of the ear hook is connected to the sound-generating device 10, and the other end is connected to the battery unit, which is used to fix the noise-canceling headphones on the user's ear. The battery unit is used to power the sound-generating device 10.

[0092] In order to achieve a better noise reduction effect, a first tuning hole is provided on the first cavity or an acoustic short-circuit tube is provided between the first cavity and the second cavity. For an active noise reduction system including feedback noise reduction, the user wearing factor will change the transfer function from the electroacoustic transducer to the first microphone 13 in the audio device to a certain extent. For example, when the radiation acoustic impedance at the first sound outlet 11 is different due to wearing, in this case, the first tuning hole is provided on the first cavity or an acoustic short-circuit tube is provided between the first cavity and the second cavity (the acoustic short-circuit tube is not marked in the attached figure). The position of the first tuning hole and the acoustic short-circuit tube will not be blocked due to wearing. Due to the existence of the first tuning hole or the acoustic short-circuit tube, the radiation impedance in front of the diaphragm of the electroacoustic transducer is composed of the first sound outlet 11 and the first tuning hole 15 or the first sound outlet 11 and the acoustic short-circuit. When the first sound outlet 11 is blocked, the radiation impedance changes little due to the presence of the first tuning hole 15 or the acoustic short-circuit tube, so that the transfer function from the electroacoustic transducer to the first microphone 13 does not change much, avoiding the instability of the feedback system and thus avoiding howling.

[0093] Embodiment 7. The present application proposes another noise-canceling headset. Please refer to Figure 1 and Figure 8. The preferred embodiment of the noise-canceling headset of the present application includes a sound-emitting device 10. The sound-emitting device 10 includes a cavity, an electroacoustic transducer, a microphone and a signal processing unit. The electroacoustic transducer is arranged in the cavity to separate the cavity into a first cavity and a second cavity. A first sound outlet 11 is provided on the first cavity, and a second sound outlet 12 is provided on the second cavity.

[0094] The microphone is close to the second sound outlet 12 and is used to collect the sound signal of the electroacoustic transducer in the second cavity and convert it into an electrical signal A2.

[0095] The signal processing unit includes a first signal processing circuit, a second signal processing circuit and a first adder. The second signal processing circuit is used to perform signal processing on the electrical signal A2, and the processed electrical signal is A12; the first signal processing circuit is used to obtain the electrical signal A before it is transmitted to the electroacoustic transducer, and process the electrical signal A into the electrical signal A11; the electrical signal A11 and the electrical signal A12 have equal amplitudes and opposite phases; the first adder is used to process the electrical signal A11 and the electrical signal A12, and the processed electrical signal is A3. The electrical signal A3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit, and the amplitude of the electrical signal A3 is zero.

[0096] The first signal processing circuit includes a first gain adjuster and a first filter electrically connected, and the second signal processing circuit includes a second gain adjuster and a second filter electrically connected. The parameters of the first gain adjuster are Gain1, the parameters of the first filter are Filter1, the parameters of the second gain adjuster are Gain2, the parameters of the second filter are Filter2, the electrical signal A11 = A*Gain1*Filter1, the electrical signal A12 = A2*Gain2*Filter2, and the electrical signal A3 satisfies:

[0097] A3=A*Gain1*Filter1+S2*Gain2*Filter2=0.

[0098] The difference between Example 7 and Example 1 is that this solution can omit the first microphone 13 in Example 1, and omits the process of the first microphone 13 collecting the sound of the first sound outlet 11, and converts the collected sound into an electrical signal. The first signal processing circuit directly obtains the electrical signal A from the circuit before transmitting it to the electroacoustic transducer. Compared with Example 1, the implementation method of this solution is simpler and can also avoid the generation of howling in the noise reduction system.

[0099] Referring to Figure 9, a further technical solution of the present application is that the microphone is also used to collect external sound signals and convert them into electrical signals B2, the second signal processing circuit is also used to process the electrical signal B2, and the processed electrical signal is B12, the first adder is used to process the electrical signals B12 and A3, and the processed electrical signal is B3, and the electrical signal B3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit, wherein B12=B2*Gain2*Filter2, B3=B12+A3=B12.

[0100] The noise signal in the target area (the space from the first sound outlet 11 to the eardrum of the human ear) is N0, and the characteristic function of the electroacoustic conversion of the electroacoustic transducer is G(s).

[0101] The technical solution of Example 8 is that the signal processing unit also includes a third signal processing circuit, which processes the electrical signals A3 and B3 processed by the first adder. The processed electrical signal is A4, and the electrical signal A4 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit. The electroacoustic transducer is also used to generate a noise reduction electrical signal based on the received electrical signal.

[0102] The third signal processing circuit includes a fourth gain adjuster and a fourth filter electrically connected to each other, a parameter of the fourth gain adjuster is Gain4, and a parameter of the fourth filter is Filter4.

[0103] In order to achieve the noise reduction effect, it is necessary to satisfy A4*G(s)+N0=0, where A4=(A3+B3)*Gain4*Filter4, where A3=0, B3=B2*Gain2*Filter2, so as to determine the specific parameters of the fourth gain adjuster parameter Gain4 and the fourth filter parameter Filter4.

[0104] 10 , the technical solution of embodiment nine is that the noise-canceling earphones further include another microphone, wherein the second microphone 14 is located near the second sound outlet 12, and the first microphone 13 is located in the first cavity; the first microphone 13 is used to collect the sound signal of the electroacoustic transducer in the first cavity and convert it into an electrical signal A1 and an external sound signal B1, the second microphone 14 is also used to collect the external sound signal and convert it into an electrical signal B2, the second signal processing circuit is further used to process the electrical signal B2, and the processed electrical signal is B12; the signal processing unit further includes a fourth signal processing circuit and a second adder, the fourth signal processing circuit is used to process the electrical signal A1 and the electrical signal B1, and the processed electrical signal is A5, the second adder is used to process the electrical signal B3, the electrical signal A3 and the electrical signal A5, and the processed electrical signal is A6, the electrical signal A6 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit, and the electroacoustic transducer is further used to generate a noise reduction electrical signal based on the received electrical signal.

[0105] The fourth signal processing circuit includes a third gain adjuster and a third filter electrically connected to each other, a parameter of the third gain adjuster is Gain3, and a parameter of the third filter is Filter3.

[0106] The characteristic function of the electroacoustic conversion of the electroacoustic transducer is G(s). After receiving the electrical signal A6, the generated noise reduction signal is A6*G(s).

[0107] In order to achieve the effect of noise reduction, it is necessary to satisfy A6*G(s)+N0=0, A6*G(s)=-N0, where

[0108] A6=(B1+A1)*Gain3*Filter3+A3+B3,

[0109] Wherein A3=0, B3=B2*Gain2*Filter2, so as to determine the specific parameters of the parameter Gain3 of the third gain adjuster and the parameter Filter3 of the fourth filter.

[0110] 11 , the technical solution of embodiment 10 is that the signal processing unit further includes a third signal processing circuit, a fourth signal processing circuit and a second adder, the fourth signal processing circuit is used to process the electrical signal S1 and the electrical signal N1, and the processed electrical signal is A7, the third signal processing circuit is used to process the electrical signal A3 and the electrical signal B3, and the processed electrical signal is A8, the second adder is used to process the electrical signal A7 and the electrical signal A8, and the processed electrical signal is A9, the electrical signal A9 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit, and the electroacoustic transducer is also used to generate a noise reduction electrical signal based on the received electrical signal.

[0111] The third signal processing circuit includes a fourth gain adjuster and a fourth filter electrically connected, wherein the parameter of the fourth gain adjuster is Gain4 and the parameter of the fourth filter is Filter4. The fourth signal processing circuit includes a third gain adjuster and a third filter electrically connected, wherein the parameter of the third gain adjuster is Gain3 and the parameter of the third filter is Filter3.

[0112] The characteristic function of the electroacoustic conversion of the electroacoustic transducer is G(s). After receiving the electrical signal A9, the generated noise reduction signal is A9*G(s).

[0113] In order to achieve the noise reduction effect, it is necessary to satisfy A9*G(s)+N0=0, A9*G(s)=-N0, where A9=A7+A8, A7=(A1+B1)*Gain3*Filter3, A8=(A3+B3)*Gain4*Filter4.

[0114] With reference to the solutions of the eighth, ninth and tenth embodiments, it can be seen that when the target noise signal N0 is the same.

[0115] A4=A6=A9.

[0116] In the fourth embodiment, A4=(A3+B3)*Gain4*Filter4;

[0117] In the fifth embodiment, A6=(B1+A1)*Gain3*Filter3+A3+B3;

[0118] In the sixth embodiment, A9=(A1+B1)*Gain3*Filter3+(A3+B3)*Gain4*Filter4

[0119] It can be seen from this that in the solution of Example 6, the parameters of Gain4 and Filter4 are different from those in Example 4, and the parameters of Gain3 and Filter3 are different from those in Example 5, that is, the electrical signal A7 is not equal to A5, and the electrical signal A8 is not equal to A4. In Example 6, the parameters of Gain4, Filter4, Gain3 and Filter3 need to be reset to achieve the purpose of eliminating the target noise signal N0.

[0120] Referring to Figure 12, a further technical solution of the present application is that the noise-canceling headphones further include a power amplifier, which is used to amplify the output signal of the signal processing unit before the electroacoustic transducer. In Example 8, A4*G(s)*K+N0=0; in Example 9, A6*G(s)*K+N0=0; and in Example 10, A9*G(s)*K+N0=0. In different embodiments, the value of K may vary depending on the needs, where K can be greater than 1 or less than 1.

[0121] To achieve the above objectives, the present application proposes another noise-canceling headphone. Referring to FIG13 , Example 11, another embodiment of the noise-canceling headphone of the present application includes a sound-generating device 20. The sound-generating device 20 includes a cavity, within which an electroacoustic transducer is disposed. The electroacoustic transducer divides the cavity into a first cavity and a second cavity. The first cavity is provided with a first sound outlet 21, and the second cavity is provided with a second sound outlet 22. Specifically, the electroacoustic transducer can be an electroacoustic transducer having a diaphragm. The diaphragm vibrates back and forth, squeezing the air in the first and second cavities, generating sound, which is then transmitted through the first sound outlet 21 and the second sound outlet 22 of the first cavity, respectively. Due to the structure of the noise-canceling headphone, when the diaphragm vibrates, the sound emitted from the first sound outlet 21 and the second sound outlet 22 have substantially the same amplitude and substantially opposite phase. The reason why the two sets of sounds are not identical in amplitude and phase is because the acoustic impedance of the electroacoustic transducer diaphragm is different. A first microphone 25 is positioned between the first sound outlet 21 and the electroacoustic transducer. A second microphone 23 is positioned on the sound-generating device 20, located near the second sound outlet 22. A first tuning hole 24 is positioned in the first cavity. For active noise reduction systems that include feedback noise reduction, the transfer function from the electroacoustic transducer to the first microphone 25 in the audio device can be altered to some extent by the user's wearing experience. For example, when the radiated acoustic impedance at the first sound outlet 21 varies due to wearing, this is achieved primarily by positioning the first tuning hole 24 in the first cavity. This prevents the first tuning hole 24 from being blocked by wearing. Due to the presence of the first tuning hole 24, the radiation impedance in front of the electroacoustic transducer's diaphragm is composed of both the first sound outlet 21 and the first tuning hole 24. Even when the first sound outlet 21 is blocked, the presence of the first tuning hole 24 minimizes the change in radiation impedance, minimizing the significant change in the transfer function from the electroacoustic transducer to the first microphone 25. This prevents instability in the feedback system and, consequently, prevents howling.

[0122] Furthermore, the center-to-center distance between the first sound hole 21 and the first tuning hole 24 is no greater than 6 mm, and the center-to-center distance between the second sound hole 22 and the first sound hole 21 is no greater than 15 mm. The first sound hole 21 and the second sound hole 22 form a pair of dipole sound sources, and the first tuning hole 24 and the second sound hole 22 form a pair of dipole sound sources. These two pairs of dipole sound sources spatially form a nearly quadrupole sound source.

[0123] Referring to Figure 14, existing open audio devices all use the front and rear diaphragms of the electroacoustic transducer unit or drive two independent diaphragms to form a dipole sound source for sound attenuation to prevent sound leakage. However, compared with a multipole sound source (such as a quadrupole sound source), a dipole sound source cannot achieve the sound leakage prevention effect of a multipole sound source, and there are problems of interfering with others or poor privacy, which affects the user experience.

[0124] The principle of dipole-to-multipole construction is as follows: a multipole sound source can be considered a combination of dipole sound sources with opposite polarity. Figure 14 shows a dipole sound source and a transverse quadrupole sound source. The dipole sound source consists of point source 1 (+Q1) and point source 2 (-Q2). Point sources 1 and 2 have the same amplitude and opposite phase, and are located at a distance d from each other. The sound pressure p at a distance r from the dipole sound source is expressed as Equation 1.

[0125] The quadrupole sound source is composed of two dipole sound sources with opposite phases. Referring to Figure 15, point sound source 1 (+Q1) and point sound source 2 (-Q2) have the same amplitude, opposite phases, and a distance of d, forming the first dipole sound source; point sound source 3 (+Q4) and point sound source 4 (-Q4) have the same amplitude and opposite phases, and a distance of d, forming the second dipole sound source; the first dipole sound source and the second dipole sound source have opposite phases and a distance of D, as shown in the spatial layout in Figure 15, forming a transverse quadrupole sound source. The sound pressure p at a certain point r away from the transverse quadrupole sound source is shown in Equation 2.

[0126] In the above expressions 1 and 2:

[0127] C - Speed ​​of sound

[0128] ρ——medium density

[0129] r——the distance from a certain position in the sound field to the sound source

[0130] d——Dipole sound source spacing

[0131] D——the distance between two dipole sound sources

[0132] Q——Surface volume velocity of sound source

[0133] k——wave node, k=2*π / λ

[0134] θ——Radiation angle of sound source.

[0135] By comparing expressions 1 and 2, the ratio between the quadrupole sound source and the dipole sound source is as shown in equation 3:

[0136] 4kDsinθ Formula (3)

[0137] When the distance between the two pairs of dipoles is small,

[0138] 4kDsinθ<1

[0139] When the amplitude of the point sound source is exactly the same, the sound pressure radiated by the quadrupole sound source is smaller than that of the dipole sound source. Therefore, it can be seen that the sound leaked out by the quadrupole sound source and the dipole sound source is smaller.

[0140] In this embodiment, the center of the first sound hole 21 is closer to the external auditory canal than the center of the first tuning hole 24, with the distance not exceeding 13 mm. The center-to-center distance between the first sound hole 21 and the first tuning hole 24 is no greater than 6 mm. The center-to-center distance between the second sound hole 22 and the first sound hole 21 is no greater than 15 mm. Compared to the first sound hole 21, the second sound hole 22 is further away from the external auditory canal (see FIG. 21 ), with the center-to-center distance not exceeding 20 mm.

[0141] Due to the directivity of the dipole sound source or the quadrupole sound source in the far sound field, a certain position in the far sound field on the sound source line has a higher sound pressure level than other positions, as shown by the angle θ in formula (2). Therefore, the second sound outlet 22 can be set on the side of the sound-emitting part to avoid the maximum sound leakage in the far sound field being located in front of or on the side of the user. In some embodiments, the second sound outlet 22 is located on the upper side or lower side of the sound-emitting part, so that the angle formed by the line connecting the centers of the second sound outlet 22 and the first sound outlet 21 and the median plane of the human body is not greater than 80°, and the angle formed by the line connecting the centers of the second sound outlet 22 and the first tuning hole 24 and the median plane of the human body is not greater than 70°.

[0142] The comparison results shown in Figure 16 show that when the sound-emitting device 20 does not have the first tuning hole 24 and the first sound outlet hole 21 is completely blocked, the change in the amplitude-frequency response is very large compared to the normal operation of the first sound outlet 21, which is about 10dB in the mid-high frequency part and more than 10dB in the low frequency part. This increases the difficulty of feedback filter design, and the noise reduction performance will be greatly sacrificed while ensuring the stability of the active noise reduction system and the absence of howling.

[0143] As shown in the comparison results shown in Figure 17, when the sound-emitting device 20 is provided with the first tuning hole 24, the change in the amplitude-frequency response after the first sound outlet 21 is completely blocked is smaller than that of the normal operation of the first sound outlet 21, and is controlled within 3dB, which is beneficial to the design of the noise reduction filter and the improvement of the active noise reduction performance.

[0144] The influence of the position of the first tuning hole 24 on the high frequency response curve is described below.

[0145] According to the basic principles of acoustics, when there are incident sound waves and reflected sound waves in a space and the wavelength of the sound waves is comparable to the size of the space, the incident sound waves and the reflected sound waves will form standing waves, thereby forming nodes and antinodes. Since the wavelength of high-frequency sound waves is shorter, such nodes and antinodes usually occur at high frequencies, thereby affecting the high-frequency sound quality. In this embodiment, the inner cavity surface of the front and rear cavities of the electroacoustic transducer diaphragm is preferably designed as an arc structure, but there are still approximately parallel surfaces and approximately parallel surfaces with the electroacoustic transducer diaphragm, thereby providing conditions for the formation of standing waves. The maximum distance from the center of the first sound outlet 21 to the inner side of the first cavity is X k , when X kThe following formula is satisfied, thereby forming an antinode at the first sound outlet 21 , that is, a maximum value of the sound, and generating a peak on the frequency response curve.

[0146] Wherein, f0 is the frequency of the standing wave antinode, that is, the frequency corresponding to the peak on the frequency response curve, c0 is the speed of sound propagation in the air, and L is the maximum distance from the center of the first sound outlet 21 to the inner side of the first cavity.

[0147] Another situation in which peaks and troughs are generated is when resonance is formed between the first front cavity and the first sound outlet 21, thereby generating peaks. The resonance frequency formula is:

[0148] Wherein, f0 is the resonant frequency between the first cavity and the first sound outlet 21, c0 is the propagation speed of sound waves in the air, S is the actual area of ​​the first sound outlet 21, V is the actual volume of the first cavity, l is the length of the first sound outlet 21, and r is the equivalent radius of the first sound outlet 21.

[0149] In this embodiment, the resonant frequency formed by the first cavity and the first sound outlet 21 is close to 5 kHz, as shown in curve a in Figure 18 , but forms a trough near 8 kHz. As can be seen, the first cavity and the first sound outlet 21 form both a peak and a trough. To improve the headphone's high-frequency bandwidth and ductility, it is necessary to shift the resonant frequency of the peak to a higher frequency and increase the sound pressure level in the trough region of the frequency response curve. In this embodiment, a first tuning hole 24 is designed on the surface of the first cavity. This effectively increases the area of ​​the sound outlet in the first cavity. As shown in Equation 6, the resonant frequency shifts to a higher frequency, as shown in curve b in Figure 18 , where the peak resonant frequency is adjusted to near 6 kHz. Furthermore, the standing wave effect at the location of the first tuning hole 24 is utilized to bring the frequency of the standing wave closer to the aforementioned trough frequency, thereby improving the frequency response curve in this frequency range and enhancing the bandwidth and ductility. Specifically, as shown in curve b in Figure 18 , the frequency response curve near 8 kHz is further improved by approximately 7 dB. According to Formula 5, in order to improve the frequency response in the frequency band near 8 kHz, the maximum distance from the center of the first tuning hole 24 to the inner cavity surface of the first cavity is between 9 and 13 mm. In some embodiments, in this embodiment, the maximum distance from the center of the first tuning hole 24 to the inner cavity side surface of the first cavity is 11 mm, and the frequency of the standing wave antinode is 8000 Hz, thereby improving the trough formed by the first tuning hole 24 and the first cavity.

[0150] In this embodiment, while standing waves are utilized to improve the headphone's frequency response curve and high-frequency sound quality, to minimize other effects of standing waves, the inner surface of the first cavity, including opposing inner surfaces perpendicular to the vibration direction of the electroacoustic transducer diaphragm, is designed to be curved, thereby minimizing the energy and probability of standing waves. In this embodiment, the inner surfaces of the first cavity located on both sides of the long axis of the electroacoustic transducer are curved. In addition, the inner surfaces are relatively inclined, which to some extent changes the incident angle of the sound wave and reduces the generation of standing waves.

[0151] It is worth mentioning that when the earphones are worn on the human ear, the sound-emitting part of the earphones covers part of the cavum concha, the crus helix, and the cymba concha. From an ergonomic point of view, the covered area will be slightly different when different people wear earphones. In order to ensure that the first sound outlet 21 of the earphones is close to the external auditory canal when worn by different people, the first sound outlet 21 should cover the external auditory canal, the suprasternal notch, the cavum concha, and the crus helix (refer to Figure 21). In some embodiments, the first sound outlet 21 has a longer dimension along the length direction of the sound-emitting part than along the height direction of the sound-emitting part, such as the long side of a runway shape, the long side of a rectangle, the long axis of an ellipse, etc. The ratio of the dimension of the first sound outlet 21 along the length direction of the sound-emitting part to the dimension along the height direction of the sound-emitting part is between 1.1-3.5.

[0152] In order to reduce the standing waves in the second cavity (back cavity), the inner cavity surface of the second cavity is designed to be an arc or a relatively inclined surface relative to the side surface. In some embodiments, there is an arc along the width direction of the sound-emitting part. The earphone is provided with an isolation plate, and the isolation plate is made of stainless steel. The stainless steel is parallel to the bottom of the electroacoustic transducer. In order to reduce the generation of standing waves, the distance between the stainless steel spacer and the bottom of the electroacoustic transducer is adjusted so that the surface distance between the isolation plate and the bottom of the electroacoustic transducer has a certain number of variations, thereby reducing the generation of standing waves. In the selected place, the distance has at least two or more different size ratios. Since the second back cavity and the second sound outlet 22 have a high-frequency resonant frequency, it also affects the frequency response curve of the earphone. In some embodiments, the larger the opening area of ​​the second sound outlet 22, the better. On the one hand, the high-frequency resonant frequency moves toward high frequency. On the other hand, the larger the second sound outlet 22, the easier it is for the air in the second cavity to be pushed by the diaphragm of the electroacoustic transducer, thereby producing better low frequency. The area ratio of the second sound hole 22 to the first sound hole 21 is between 1-2. Considering the product appearance, the second sound hole 22 has a larger size than the first sound hole 21 in the length direction of the sound part. The size ratio is between 1.5-3.

[0153] In this embodiment, the distance between the sound pickup hole of the second microphone 23 and the center of the second sound outlet 22 is no greater than 5 mm. In traditional noise-canceling headphone designs, the sound pickup hole of the second microphone 23 is placed as far away from the sound outlet as possible. This minimizes the microphone's ability to pick up sound from the electroacoustic transducer and instead picks up only external noise. This is the basis for noise reduction design. In particular, the second microphone 23 is typically designed to be far away from the second sound outlet 22. In many noise-canceling headphones, the second microphone 23 is even positioned at the acoustic zero point of the acoustic dipole radiation field formed by the first sound outlet 21 and the second sound outlet 22, completely blocking the second microphone 23 from picking up sound from the electroacoustic transducer. These designs can lead to inaccurate noise detection by the noise reduction system, resulting in poor noise reduction performance and even causing howling. This solution differs from the aforementioned technical approach by placing the first microphone 25 as close as possible to the first sound outlet 21 and the second microphone 23 as close as possible to the second sound outlet 22. For example, the center distance between the sound pickup hole of the first microphone 25 and the first sound outlet 21 can be set to no more than 5 mm based on actual conditions. The center distance between the sound pickup hole of the second microphone 23 and the second sound outlet 22 can also be set to no more than 5mm according to actual conditions. This facilitates the first microphone 25 to collect sound from the first sound outlet 21, and the second microphone 23 to collect sound from the second sound outlet 22. As can be seen from the above solution, in this embodiment, by providing an anti-howling circuit, the sound signals collected by the first microphone 25 and the sound signals collected by the second microphone 23 will be completely offset in the noise reduction system and will not be transmitted back to the electroacoustic transducer. Compared with solutions that design the microphones far away from the sound outlet, this solution has better noise reduction and anti-howling effects.

[0154] The sound pickup hole of the first microphone 25 is no more than 5 mm away from the center point of the first sound outlet hole 21 and the first tuning hole 24. The sound pickup hole of the first microphone 25 is close to the first sound outlet hole 21 and the first tuning hole 24 to facilitate the collection of sound signals from the first sound outlet hole 21.

[0155] Furthermore, the first microphone 25, while being used for active noise reduction, can also be used for communication, collaborating with the noise-canceling headphone circuit system to achieve a call function. Due to the location of the first microphone 25, it can be combined with the structural features of the first sound outlet 21, the first tuning hole 24, and the first cavity to avoid picking up external wind noise during communication, thereby achieving a good call quality.

[0156] Referring to Figures 22-23, a specific description is given of a scenario where the user is in headwind. The headwind blows from the front of the human body to the face, and then blows to the ears or headphones; or when the person is in motion, the direction of the wind is opposite to the direction of movement of the person. Specifically, as shown in Figure 23, the noise-canceling headphones are worn on a right ear auricle model. In order to more clearly show the first tuning hole 24, the first sound outlet 21, and the first microphone 25 on the noise-canceling headphones, the right ear auricle model is not shown in Figure 23. For ease of description, the headwind direction shown in Figure 23 is from left to right, which corresponds to the headwind direction from the front to the back of the human body in actual application scenarios, so that the headphones are affected by the headwind.

[0157] Referring to Figure 23 , the oncoming wind flows from left to right, first affecting the first tuning hole 24 and then the first sound outlet 21. In this design, a steel mesh is placed over the first sound outlet 21 and the first tuning hole 24. An acoustic mesh is placed beneath the steel mesh over the first sound outlet 21 and the first tuning hole 24. The acoustic mesh attached to the first sound outlet 21 and the first sound outlet 24 provides a certain degree of wind resistance, thereby reducing the wind noise energy reaching the first microphone 25.

[0158] Furthermore, after the wind blows into the front cavity through the first tuning hole 24 , the wind can move along the front cavity toward the first sound outlet hole 21 and be blown out quickly.

[0159] The first tuning hole 24 and the first sound outlet 21, as well as the mesh and steel mesh attached to the first tuning hole 24, the mesh and steel mesh attached to the first sound outlet 21, and the front cavity, disperse and channel wind energy to prevent wind from directly impacting the first microphone 25, thereby reducing wind noise. Furthermore, to allow wind energy to quickly dissipate from the first sound outlet 25, the first sound outlet 21 can be shaped as a rectangle, a runway, or an ellipse. When the first tuning hole 21 is rectangular or runway-shaped, the length of the long side of the first sound outlet 21 is 2 to 5 times the length of the short side. When the first tuning hole 21 is elliptical, the length of the long axis of the first sound outlet 21 is 2 to 5 times the length of the short axis. Referring to Figure 23, the first sound outlet 21 is larger in the direction facing the wind than perpendicular to the direction facing the wind. This design manifests itself in the earphone as the first sound outlet 21 being larger along the length of the sound-emitting portion than along its height, with the ratio between the two and five times.

[0160] Furthermore, in order to prevent the wind energy entering the front cavity from acting on the first microphone 25, the sound pickup hole of the first microphone 25 is located next to the first sound outlet hole 21, and in some embodiments, is located on the long side of the first sound hole, and the position of the sound pickup hole of the first microphone 25 avoids the opening interval between the first tuning hole 24 and the first sound outlet hole 21, so as to prevent the wind from flowing into the sound pickup hole of the first microphone 25 when flowing from the first tuning hole 24 to the first sound outlet hole 21.

[0161] In actual application scenarios, the noise-canceling headphones will also be exposed to wind from other directions, such as wind directions perpendicular to the outer side of the human headphones. Since the first microphone 25 is located in the front cavity close to the first sound outlet 25, the cavity can form a windbreak for the first microphone 25, blocking the wind from directly acting on the sound pickup hole of the first microphone 25, which can effectively reduce the energy of wind noise picked up by the first microphone 25, thereby improving the call quality.

[0162] A further technical solution of the present application is that the sound pickup hole of the first microphone 25 faces the diaphragm of the electroacoustic transducer. In some embodiments, the sound pickup hole of the first microphone 25 faces the diaphragm of the electroacoustic transducer and is away from the steel mesh of the first sound outlet 21, thereby preventing wind energy from acting on the microphone diaphragm and further reducing wind noise.

[0163] A further technical solution of the present application is that the sound pickup hole of the first microphone 25 is located next to the first sound outlet hole 21, the distance between the sound pickup hole of the first microphone 25 and the edge of the first sound outlet hole 21 is between 3mm and 5mm, and the center distance between the sound pickup hole of the first microphone 25 and the first tuning hole 24 is greater than 5mm.

[0164] A further technical solution of the present application is that the first surface is designed to be curved. The curved design can facilitate smooth outflow of wind speed and change wind direction when wind acts on the earphone, reducing the wind energy acting on the first tuning hole 24 and the first sound outlet 21. Furthermore, the first surface is designed with a raised structure, and the first sound outlet 21 is located on the end surface of the raised structure. The raised structure has a certain curved design from the first surface to the end surface, and the raised structure can also play a role in blocking and dispersing wind. The angle between the plane where the end surface is located and the plane where the diaphragm of the electroacoustic transducer is located is between 30 degrees and 60 degrees.

[0165] Through the above specific embodiments, professionals in this field can easily think of suboptimal solutions, such as removing the first tuning hole based on the above solution, or adjusting the direction of the pickup hole of the first microphone 25 so that the pickup hole of the first microphone 25 faces away from the diaphragm of the electroacoustic transducer. The first microphone 25 is still inside the front cavity, and the front cavity can provide a windbreak for the pickup hole of the first microphone 25, thereby reducing the wind noise energy picked up by the pickup hole of the first microphone 25. A further technical solution of the present application is that, with reference to Figure 19, the noise reduction headset also includes a third microphone. The third microphone and the second microphone 23 cooperate with a directional algorithm to form a dual-microphone call noise reduction. The front and rear microphones are used for directional processing. The sound signal obtained by the third microphone needs to be delayed to ensure that it arrives at the same time as the rear signal received by the second microphone 23. The signal of the third microphone is then subtracted from the signal of the second microphone 23, so that the front sound signal is retained to obtain a directional effect.

[0166] A further technical solution of the present application is that when a standard human model wears the noise-canceling headphones, the angle between the straight line between the sound pickup hole of the second microphone 23 and the center point of the mouth and the straight line formed by the sound pickup hole of the third microphone and the center point of the mouth is less than 30 degrees. In some embodiments, when the noise-canceling headphones are worn, the sound pickup hole of the third microphone, the sound pickup hole of the second microphone 23, and the center point of the user's mouth are in a straight line, or the straight line connecting the sound pickup hole of the third microphone and the sound pickup hole of the second microphone 23 is as close as possible to the center point of the mouth, so as to better pick up the user's voice.

[0167] A further technical solution of the present application is that the distance between the sound pickup hole of the third microphone and the sound pickup hole of the second microphone 23 is greater than 15 mm.

[0168] A further technical solution of the present application is that the distance between the sound pickup hole of the second microphone 23 and the edges of the first sound outlet hole 21 and the first tuning hole 24 is greater than 10 mm.

[0169] A further technical solution of the present application is to provide an acoustic short-circuit tube between the first cavity and the second cavity (the acoustic short-circuit tube is not marked in the attached drawings). Providing an acoustic short-circuit tube between the first cavity and the second cavity can be an alternative to providing the first tuning hole 24 or a supplementary solution after providing the first tuning hole 24. As mentioned above, by providing the acoustic short-circuit tube between the first cavity and the second cavity, the radiation impedance in front of the diaphragm of the electroacoustic transducer is composed of the first sound outlet hole 21 and the first tuning hole 24 or the first sound outlet hole 21 and the acoustic short-circuit. When the first sound outlet hole 21 is blocked, the radiation impedance changes little due to the presence of the first tuning hole 24 or the acoustic short-circuit tube, so that the transfer function from the electroacoustic transducer to the first microphone 25 will not change too much, thereby avoiding the instability of the feedback system and thus avoiding howling.

[0170] To achieve the above objectives, the present application also proposes a headphone noise reduction method, which is applied to noise-canceling headphones. The noise-canceling headphones include an electroacoustic transducer, a first microphone 25, a second microphone 23, and a signal processing unit. The signal processing unit includes a first signal processing circuit, a second signal processing circuit, and a first adder. The first microphone 25 is used to collect the sound signal of the electroacoustic transducer in the first cavity and convert it into an electrical signal S1. The second microphone 23 is used to collect the sound signal of the electroacoustic transducer in the second cavity and convert it into an electrical signal S2. Referring to Figure 20, a first embodiment of the method includes the following steps:

[0171] Step 1: The first microphone 25 collects the sound signal of the electroacoustic transducer in the first cavity and converts it into an electrical signal S1;

[0172] Step 2: The second microphone 23 collects the sound signal of the electroacoustic transducer in the second cavity and converts it into an electrical signal S2;

[0173] Step 3: The first signal processing circuit processes the electrical signal S1 to produce a processed electrical signal S11. The second signal processing circuit processes the electrical signal S2 to produce a processed electrical signal S12. The electrical signals S11 and S12 have equal amplitudes and opposite phases.

[0174] Step 4: The first adder processes the electrical signal S11 and the electrical signal S12. The processed electrical signal is S3. The electrical signal S3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit. The amplitude of the electrical signal S3 is zero.

[0175] The first signal processing circuit includes a first gain adjuster and a first filter electrically connected, and the second signal processing circuit includes a second gain adjuster and a second filter electrically connected. The parameter of the first gain adjuster is Gain1, the parameter of the first filter is Filter1, the parameter of the second gain adjuster is Gain2, the parameter of the second filter is Filter2, the electrical signal S11 = S1*Gain1*Filter1, the electrical signal S12 = S2*Gain2*Filter2, and the electrical signal S3 satisfies:

[0176] S3=S1*Gain1*Filter1+S2*Gain2*Filter2=0.

[0177] After the above conditions are met, the parameters of the first signal processing circuit and the second signal processing circuit are kept unchanged. In this embodiment, the first gain adjuster and the first filter, the second gain adjuster and the second filter keep the set parameters unchanged so that the electrical signal S3 meets the above conditions.

[0178] In this embodiment, the first signal processing circuit processes the electrical signal S1 to obtain a processed electrical signal S11, and the second signal processing circuit processes the electrical signal S2 to obtain a processed electrical signal S12. The electrical signals S11 and S12 have equal amplitudes and opposite phases. The electrical signals S11 and S12 are then processed by a first adder so that the signal transmitted to the electroacoustic transducer is zero, which greatly improves the active noise reduction performance of the headphones and does not generate howling. When the user uses open headphones but does not want to hear external sounds, it provides the user with an excellent immersive experience.

[0179] Based on the first embodiment proposed in FIG20 , a second embodiment of the headphone noise reduction method of the present application is proposed. The difference between this embodiment and the first embodiment shown in FIG13 is that the first microphone 25 is further used to collect external sound signals and convert them into electrical signals N1, and the second microphone 23 is further used to collect external sound signals and convert them into electrical signals N2;

[0180] Step 1 also includes: the first microphone 25 collects external sound signals and converts them into electrical signals N1;

[0181] Step 2 also includes: the second microphone 23 collects external sound signals and converts them into electrical signals N2;

[0182] Step 3 further includes: a first signal processing circuit processes the electrical signal N1, and the processed electrical signal is N11; a second signal processing circuit processes the electrical signal N2, and the processed electrical signal is N12;

[0183] Step 4 further includes: a first adder processes the electrical signal N11 and the electrical signal N12, the processed electrical signal being N3, and the electrical signal N3 being transmitted to the electroacoustic transducer as an output signal of the signal processing unit.

[0184] Specifically, as an embodiment, the signal processing circuit further includes a third signal processing circuit, and step 4 further includes:

[0185] Step 5: The third signal processing circuit processes the electrical signals S3 and N3 processed by the first adder. The processed electrical signal is S4, and the electrical signal S4 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit.

[0186] Step 6: The electroacoustic transducer is further configured to generate a noise reduction electrical signal based on the received electrical signal.

[0187] As another embodiment, the signal processing unit further includes a fourth signal processing circuit and a second adder, and before Step 4, the following steps are further included:

[0188] In step 41, the fourth signal processing circuit processes the electrical signal S1 and the electrical signal N1, and the processed electrical signal is S5. After step 4, the following steps are further included:

[0189] Step 42: a second adder processes the electrical signal S3, the electrical signal N3, and the electrical signal S5. The processed electrical signal is S6, and the electrical signal S6 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit.

[0190] In step 43, the electroacoustic transducer generates a noise reduction signal according to the received electrical signal.

[0191] As another embodiment, the signal processing unit further includes a third signal processing circuit, a fourth signal processing circuit and a second adder, and before Step 4, the following steps are further included:

[0192] Step 41: The fourth signal processing circuit processes the electrical signal S1 and the electrical signal N1. The processed electrical signal is S7.

[0193] Step 4 and later also include:

[0194] Step 42: a third signal processing circuit processes the electrical signal S3 and the electrical signal N3, and the processed electrical signal is S8;

[0195] Step 43: a second adder processes the electrical signal S7 and the electrical signal S8 to obtain a processed electrical signal S9, which is transmitted to the electroacoustic transducer as an output signal of the signal processing unit.

[0196] In step 44, the electroacoustic transducer generates a noise reduction electrical signal according to the received electrical signal.

[0197] In this embodiment, the noise-canceling headphones may further include a power amplifier, and the step Step 43 further includes: amplifying the electrical signal S9 by the power amplifier.

[0198] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A noise-cancelling headset, characterized in that: The noise reduction headset comprises a sound-generating device, and the sound-generating device comprises: a cavity, an electroacoustic transducer, a first microphone, a second microphone and a signal processing unit; The electroacoustic transducer is arranged in the cavity, and the cavity is divided into a first cavity and a second cavity, the first cavity is provided with a first sound outlet hole, and the second cavity is provided with a second sound outlet hole; The first microphone is disposed in the first cavity, and is used to collect the sound signal of the electroacoustic transducer in the first cavity and convert it into an electrical signal S1; The second microphone is close to the second sound outlet and is used to collect the sound signal of the electroacoustic transducer in the second cavity and convert it into an electrical signal S2; The signal processing unit includes a first signal processing circuit, a second signal processing circuit and a first adder. The first signal processing circuit is used to perform signal processing on the electrical signal S1, and the processed electrical signal is S11. The second signal processing circuit is used to perform signal processing on the electrical signal S2, and the processed electrical signal is S12. The electrical signal S11 and the electrical signal S12 have equal amplitudes and opposite phases. The first adder is used to process the electrical signal S11 and the electrical signal S12, and the processed electrical signal is S3. The electrical signal S3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit, and the amplitude of the electrical signal S3 is zero.

2. The noise-cancelling earphone according to claim 1, characterized in that: The center distance between the sound pickup hole of the first microphone and the first sound output hole is no more than 5 mm.

3. The noise-cancelling earphone according to claim 1, characterized in that: The center distance between the sound pickup hole of the second microphone and the second sound output hole is no more than 5 mm.

4. The noise-cancelling earphone according to claim 1, characterized in that: The first microphone is also used to collect external sound signals and convert them into electrical signals N1, and the second microphone is also used to collect external sound signals and convert them into electrical signals N2; the first signal processing circuit is also used to process the electrical signal N1, and the processed electrical signal is N11, the second signal processing circuit is also used to process the electrical signal N2, and the processed electrical signal is N12, the first adder is also used to process the electrical signals N11 and N12, and the processed electrical signals are N3, and the electrical signal N3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit.

5. The noise-cancelling earphone according to claim 4, characterized in that: The signal processing unit also includes a third signal processing circuit, which processes the electrical signals S3 and N3 processed by the first adder. The processed electrical signal is S4. The electrical signal S4 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit. The electroacoustic transducer is also used to generate a noise reduction electrical signal based on the received electrical signal.

6. The noise-cancelling earphone according to claim 4, characterized in that: The signal processing unit also includes a fourth signal processing circuit and a second adder. The fourth signal processing circuit is used to process the electrical signal S1 and the electrical signal N1, and the processed electrical signal is S5. The second adder is used to process the electrical signal S3, the electrical signal N3 and the electrical signal S5, and the processed electrical signal is S6. The electrical signal S6 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit. The electroacoustic transducer is also used to generate a noise reduction electrical signal based on the received electrical signal.

7. The noise-cancelling earphone according to claim 4, characterized in that: The signal processing unit also includes a third signal processing circuit, a fourth signal processing circuit and a second adder. The fourth signal processing circuit is used to process the electrical signal S1 and the electrical signal N1, and the processed electrical signal is S7. The third signal processing circuit is used to process the electrical signal S3 and the electrical signal N3, and the processed electrical signal is S8. The second adder is used to process the electrical signal S7 and the electrical signal S8, and the processed electrical signal is S9. The electrical signal S9 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit. The electroacoustic transducer is also used to generate a noise reduction electrical signal based on the received electrical signal.

8. The noise-cancelling earphone according to any one of claims 1 to 7, characterized in that: The noise reduction headset further includes a power amplifier, which is used to amplify the output signal of the signal processing unit before the electroacoustic transducer.

9. The noise-cancelling earphone according to claim 1, characterized in that: The first signal processing circuit includes an electrically connected first gain adjuster and a first filter, the second signal processing circuit includes an electrically connected second gain adjuster and a second filter, the parameter of the first gain adjuster is Gain1, the parameter of the first filter is Filter1, the parameter of the second gain adjuster is Gain2, the parameter of the second filter is Filter2, the electrical signal S11 is S1*Gain1*Filter1, the electrical signal S12 is S2*Gain2*Filter2, and the electrical signal S3 satisfies: S3=S1*Gain1*Filter1+S2*Gain2*Filter2=0.

10. The noise-cancelling earphone according to claim 5 or 7, characterized in that: The third signal processing circuit includes a fourth gain adjuster and a fourth filter which are electrically connected. The parameter of the fourth gain adjuster is Gain4, and the parameter of the fourth filter is Filter4.

11. The noise-cancelling earphone according to claim 6 or 7, characterized in that: The fourth signal processing circuit includes a third gain adjuster and a third filter which are electrically connected. The parameter of the third gain adjuster is Gain3, and the parameter of the third filter is Filter3.

12. The noise-cancelling earphone according to any one of claims 5 to 7, characterized in that: The electroacoustic transducer is further configured to generate a noise reduction audio signal according to the noise reduction electrical signal.

13. The noise-cancelling earphone according to claim 1, characterized in that: The noise reduction headset also includes an ear hook and a battery unit. One end of the ear hook is connected to the sound-generating device, and the other end is connected to the battery unit, so as to fix the noise reduction headset on the ear.

14. The noise-cancelling earphone according to any one of claims 1 to 7, characterized in that: A first tuning hole is arranged on the first cavity and / or an acoustic short-circuit tube is arranged between the first cavity and the second cavity.

15. A noise reduction headset, characterized in that: The noise reduction headset comprises: a sound-generating device, wherein the sound-generating device comprises a cavity, an electroacoustic transducer, a microphone and a signal processing unit; The electroacoustic transducer is arranged in the cavity, and the cavity is divided into a first cavity and a second cavity, the first cavity is provided with a first sound outlet hole, and the second cavity is provided with a second sound outlet hole; The microphone is close to the second sound outlet and is used to collect the sound signal of the electroacoustic transducer in the second cavity and convert it into an electrical signal A2; The signal processing unit includes a first signal processing circuit, a second signal processing circuit and a first adder, the second signal processing circuit is used to perform signal processing on the electrical signal A2, and the processed electrical signal is A12; the first signal processing circuit is used to obtain the electrical signal A before it is transmitted to the electroacoustic transducer, and process the electrical signal A into the electrical signal A11; the electrical signal A11 and the electrical signal A12 have the same amplitude and opposite phase; the first adder is used to process the electrical signal A11 and the electrical signal A12, and the processed electrical signal is A3, the electrical signal A3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit, and the amplitude of the electrical signal A3 is zero.

16. A noise reduction headset, characterized in that: The noise reduction earphones include: a sound-emitting device, the sound-emitting device includes a cavity, an electroacoustic transducer is arranged in the cavity, the electroacoustic transducer separates the cavity into a first cavity and a second cavity, the first cavity is provided with a first sound outlet hole, and the second cavity is provided with a second sound outlet hole; the first microphone is arranged between the first sound outlet hole and the electroacoustic transducer, the sound-emitting device is provided with a second microphone, the second microphone is close to the second sound outlet hole, a first tuning hole is provided on the first cavity, the center distance between the first sound outlet hole and the first tuning hole is not greater than 6 mm, and the center distance between the second sound outlet hole and the center of the first sound outlet hole is not greater than 15 mm.

17. The noise-cancelling earphone according to claim 16, characterized in that: The vertical distance between the sound pickup hole of the first microphone and the straight line where the center points of the first sound outlet hole and the first tuning hole are located is no more than 5 mm.

18. The noise-cancelling earphone according to claim 16, characterized in that: The first sound outlet hole and the first tuning hole are provided with steel meshes.

19. The noise-cancelling earphone according to claim 18, characterized in that: An acoustic mesh is arranged under the steel mesh on the first sound outlet hole and the first tuning hole.

20. The noise-cancelling earphone according to claim 16, characterized in that: The first microphone and its sound pickup hole are close to the first sound outlet hole.

21. The noise-cancelling earphone according to claim 20, characterized in that: The sound pickup hole of the first microphone faces the diaphragm of the electroacoustic transducer.

22. The noise-cancelling earphone according to claim 16, characterized in that: The center distance between the sound pickup hole of the second microphone and the second sound output hole is no more than 5 mm.

23. The noise-cancelling earphone according to claim 16, characterized in that: The shape of the first sound outlet hole is one of a rectangle, a racetrack, and an ellipse. The length of the long side of the first sound outlet hole is 2 to 5 times the length of the short side. The sound pickup hole of the first microphone is close to the long side of the first sound outlet hole.

24. The noise-cancelling earphone according to claim 16, characterized in that: The sound pickup hole of the first microphone is located beside the first sound outlet hole, the distance between the sound pickup hole of the first microphone and the edge of the first sound outlet hole is between 3mm and 5mm, and the center distance between the sound pickup hole of the first microphone and the first tuning hole is greater than 5mm.

25. The noise-cancelling earphone according to claim 16, characterized in that: The first sound outlet hole and the first tuning hole are arranged on the first surface of the first cavity, and the first surface is the surface of the sound-emitting device that is closest to the helix crus when the user wears the noise-cancelling headphones. The first sound outlet hole and the first tuning hole form acoustic coupling with the electroacoustic transducer through the first cavity.

26. The noise-cancelling earphone according to claim 25, characterized in that: The edge distance between the first sound outlet hole and the first tuning hole is no greater than 4 mm.

27. The noise-cancelling earphone according to claim 25, characterized in that: The first surface is designed to be arc-shaped.

28. The noise-cancelling earphone according to claim 27, characterized in that: A protruding structure is provided on the first surface, an end surface is provided on the protruding structure, the first sound outlet is provided on the end surface, and an angle between a plane where the end surface is located and a plane where the diaphragm of the electroacoustic transducer is located is between 30 degrees and 60 degrees.

29. The noise-cancelling earphone according to claim 28, characterized in that: The protruding structure is designed to be in a certain arc shape from the first surface to the end surface.

30. The noise-cancelling earphone according to claim 16, characterized in that: The sound pickup hole of the second microphone is located beside the second sound outlet hole, and the distance between the sound pickup hole of the second microphone and the edge of the second sound outlet hole is no more than 5 mm.

31. The noise-cancelling earphone according to claim 30, characterized in that: The noise reduction headset also includes a third microphone, and the third microphone cooperates with the second microphone with a directional algorithm to form a dual-microphone call noise reduction.

32. The noise-cancelling earphone according to claim 31, characterized in that: When the standard human model wears the noise reduction headset, the angle between the straight line between the sound pickup hole of the second microphone and the center point of the mouth and the straight line formed by the sound pickup hole of the third microphone and the center point of the mouth is less than 30 degrees.

33. The noise-cancelling earphone according to claim 31, characterized in that: The distance between the sound pickup hole of the third microphone and the sound pickup hole of the second microphone is greater than 15 mm.

34. The noise-cancelling earphone according to claim 30, characterized in that: The distances between the sound pickup hole of the second microphone and the edges of the first sound outlet hole and the first tuning hole are all greater than 10 mm.

35. The noise reduction headset according to claim 16, characterized in that: An acoustic short-circuit tube is arranged between the first cavity and the second cavity.

36. A method for reducing noise in headphones, characterized in that: The headphone noise reduction method is applied to a noise reduction headphone, the noise reduction headphone comprises an electroacoustic transducer, a first microphone, a second microphone and a signal processing unit, the signal processing unit comprises a first signal processing circuit, a second signal processing circuit and a first adder, the first microphone is used to collect the sound signal of the electroacoustic transducer in the first cavity and convert it into an electrical signal S1, the second microphone is used to collect the sound signal of the electroacoustic transducer in the second cavity and convert it into an electrical signal S2, the method comprises the following steps: The first microphone collects the sound signal of the electroacoustic transducer in the first cavity and converts it into an electrical signal S1; The second microphone collects the sound signal of the electroacoustic transducer in the second cavity and converts it into an electrical signal S2; The first signal processing circuit performs signal processing on the electrical signal S1, and the processed electrical signal is S11; the second signal processing circuit performs signal processing on the electrical signal S2, and the processed electrical signal is S12; the electrical signal S11 and the electrical signal S12 have equal amplitudes and opposite phases; The first adder processes the electrical signal S11 and the electrical signal S12. The processed electrical signal is S3. The electrical signal S3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit. The amplitude of the electrical signal S3 is zero.

37. The headphone noise reduction method according to claim 36, characterized in that: The first microphone is also used to collect external sound signals and convert them into electrical signals N1, and the second microphone is also used to collect external sound signals and convert them into electrical signals N2; The first microphone collects the sound signal of the electroacoustic transducer in the first cavity and converts it into an electrical signal S1, and further includes: the first microphone collects the external sound signal and converts it into an electrical signal N1; The second microphone collects the sound signal of the electroacoustic transducer in the second cavity and converts it into an electrical signal S2, and further includes: the second microphone collects the external sound signal and converts it into an electrical signal N2; The first signal processing circuit performs signal processing on the electrical signal S1, and the processed electrical signal is S11; the second signal processing circuit performs signal processing on the electrical signal S2, and the processed electrical signal is S12; the electrical signals S11 and S12 have equal amplitudes and opposite phases; and further comprising: the first signal processing circuit processes the electrical signal N1, and the processed electrical signal is N11; the second signal processing circuit processes the electrical signal N2, and the processed electrical signal is N12; The first adder processes the electrical signal S11 and the electrical signal S12, and the processed electrical signal is S3. The electrical signal S3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit, and the amplitude of the electrical signal S3 is zero. It also includes: the first adder processes the electrical signal N11 and the electrical signal N12, and the processed electrical signal is N3. The electrical signal N3 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit.

38. The headphone noise reduction method according to claim 37, characterized in that: The signal processing circuit further includes a third signal processing circuit, which further includes: The third signal processing circuit processes the electrical signals S3 and N3 processed by the first adder, and the processed electrical signal is S4, and the electrical signal S4 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit; The electroacoustic transducer is also used to generate a noise reduction electrical signal according to the received electrical signal.

39. The headphone noise reduction method according to claim 37, characterized in that: The signal processing unit further includes a fourth signal processing circuit and a second adder, and before the first adder processes the electrical signal S11 and the electrical signal S12, further includes: The fourth signal processing circuit processes the electrical signal S1 and the electrical signal N1, and the processed electrical signal is S5; After the first adder processes the electrical signal S11 and the electrical signal S12, the method further includes: The second adder processes the electric signal S3, the electric signal N3 and the electric signal S5, and the processed electric signal is S6, and the electric signal S6 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit; The electroacoustic transducer generates a noise reduction signal based on the received electrical signal.

40. The headphone noise reduction method according to claim 37, characterized in that: The signal processing unit further includes a third signal processing circuit, a fourth signal processing circuit and a second adder, and before the first adder processes the electrical signal S11 and the electrical signal S12, further includes: The fourth signal processing circuit processes the electrical signal S1 and the electrical signal N1, and the processed electrical signal is S7. After the first adder processes the electrical signal S11 and the electrical signal S12, the method further includes: The third signal processing circuit processes the electrical signal S3 and the electrical signal N3, and the processed electrical signal is S8; The second adder processes the electrical signal S7 and the electrical signal S8, and the processed electrical signal is S9, and the electrical signal S9 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit; The electroacoustic transducer generates a noise reduction electrical signal according to the received electrical signal.

41. The headphone noise reduction method according to claim 40, characterized in that: The noise reduction headphones also include a power amplifier. The second adder processes the electrical signal S7 and the electrical signal S8. The processed electrical signal is S9. The electrical signal S9 is transmitted to the electroacoustic transducer as the output signal of the signal processing unit. The method also includes: amplifying the electrical signal S9 by the power amplifier.

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