Electroacoustic transducer
The electroacoustic transducer addresses noise reduction challenges by combining FB and FF methods with strategically placed microphones to effectively reduce noise without degrading sound quality, achieving high-quality audio reproduction.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- AUDIO TECHNICA CORP
- Filing Date
- 2025-06-24
- Publication Date
- 2026-06-18
Smart Images
Figure JP2025022702_18062026_PF_FP_ABST
Abstract
Description
Electroacoustic transducer 【0001】 The present invention relates to an electroacoustic transducer having a noise reduction function. 【0002】 Conventionally, electroacoustic transducers including headphones and earphones are widely used as devices for converting an audio signal into sound for listening. In this type of electroacoustic transducer, a noise cancellation mechanism is implemented to reduce noise from the external environment incident from outside the device and enable listening to high-quality sound. 【0003】 As a method for realizing this type of noise cancellation mechanism, there are a feedforward method (hereinafter referred to as the FF method) and a feedback method (hereinafter referred to as the FB method) as an active method for achieving active noise reduction (Patent Document 1). Furthermore, a noise cancellation mechanism that combines the FF method and the FB method is provided. 【0004】 A noise cancellation mechanism that employs the FF method includes, for example, a feedforward (FF) microphone as a sound collection means for collecting noise generated in the external environment of headphones worn on the head. This FF microphone is installed outside the housing equipped with the speaker unit of the headphones to collect external environmental noise. The noise collected by the FF microphone is input to a noise cancellation signal generation circuit. The noise cancellation signal generation circuit analyzes the noise collected by the FF microphone and predicts the change in the noise until it reaches the playback sound listening point of the listener. Based on this prediction result, the noise cancellation signal generation circuit performs appropriate filtering processing on the noise to generate a noise cancellation signal having a phase opposite to that of the noise. The noise cancellation signal is added to the audio signal output from the sound source connected to the electroacoustic transducer and input to the speaker unit. The speaker unit reproduces the audio signal from the sound source together with the noise cancellation signal, thereby reducing the noise input to the headphones and enabling listening to the playback sound in a good acoustic space. 【0005】Headphones equipped with a fast-forward (FF) noise cancellation mechanism are less susceptible to interference from the reproduced sound emitted from the speaker unit because the FF microphone is placed at a relatively large distance from the speaker unit or separated by a partition. Therefore, it is possible to reduce the factors that cause feedback, while simultaneously minimizing the impact on the sound quality of the reproduced sound emitted from the speaker unit. 【0006】 On the other hand, the FF (Flash Firing) type noise cancellation mechanism operates in the opposite phase to the noise. In order to generate a noise cancellation signal that effectively reduces noise, it is necessary to properly analyze the noise collected according to the headphone usage environment and to appropriately predict the changes in the noise collected by the FF microphone. Therefore, the noise reduction effect of the FF type noise cancellation mechanism tends to decrease with respect to gain fluctuations in the noise cancellation signal generation system. 【0007】 The FB (feedback) noise cancellation mechanism uses a feedback microphone, which is the sound collection means, to collect noise transmitted from the external environment and the reproduced sound with the noise cancellation signal at the music listening position of the listener wearing headphones. The music listening position is the sound synthesis position where the noise and the reproduced sound with the noise reduction audio signal are combined, and is the noise cancellation point. Therefore, the FB noise cancellation mechanism places the FB microphone at the noise cancellation point, which is the sound synthesis position located inside the housing equipped with the speaker unit. The noise cancellation point is located on the front side of the diaphragm of the speaker unit, close to the listener's ear, and is within the internal area surrounded by the ear pads provided on the housing. 【0008】 The FB (Flashback) noise cancellation mechanism analyzes the noise collected by the FB microphone sequentially using a noise reduction circuit, generating a noise cancellation signal that minimizes noise at the music listening position. Therefore, it has the advantage of excellent responsiveness to changes in noise components. Furthermore, the noise reduction effect of the FB noise cancellation mechanism can be improved as the gain of the noise cancellation signal generation system increases. 【0009】Furthermore, conventional electroacoustic converters, including headphones and earphones, are equipped with either FF (fast-forward) or FB (fast-forward) noise cancellation mechanisms, or are equipped with both FF and FB noise cancellation mechanisms. 【0010】 Patent Document 1: Japanese Unexamined Patent Publication No. 2008-122729 【0011】 Incidentally, in the case of FF-type noise cancellation mechanisms, the noise is in opposite phase to the noise, and in order to generate a noise-reduced audio signal that effectively reduces noise, it is necessary to appropriately analyze the noise collected according to the usage environment of electroacoustic transducers such as headphones, and to appropriately predict the changes in the noise collected by the FF microphone. However, when there are fluctuations in the signal characteristics as the noise reaches the listening point, it is difficult to appropriately predict the changes in the noise. Therefore, it is difficult for FF-type noise cancellation mechanisms to perform an appropriate noise reduction function in response to gain fluctuations in the noise-canceling signal generation system. 【0012】 Furthermore, the FB (feedback) type noise cancellation mechanism is more prone to howling than the FF (fast-forward) type noise cancellation mechanism, and has the problem of having a greater impact on the reproduction characteristics of the sound radiated from the speaker unit. 【0013】 The technical objective of the present invention is to provide an electroacoustic converter that achieves appropriate noise reduction functionality and enables a reduction in the degradation of sound quality of reproduced sound. 【0014】 Furthermore, the technical problem of the present invention is to provide an electroacoustic converter that can reduce noise without complicating the configuration. Means for solving the problem 【0015】The present invention, proposed to solve the above-mentioned technical problems, is an electroacoustic transducer including headphones or earphones, comprising: a housing; a speaker unit equipped within the housing; a first sound collection means installed in the rear chamber of the housing facing the rear side of the speaker unit, for collecting reproduced sound radiated from the speaker unit and noise components incident into the rear chamber from outside the housing; a first noise cancellation signal generation means for generating a first noise cancellation signal that reduces the noise components collected by the first sound collection means; and a drive signal generation means for generating a drive signal to drive the speaker unit. 【0016】 In this electroacoustic converter, the drive signal generation means synthesizes the playback audio signal supplied from the playback sound source with the first noise cancellation signal to generate a drive signal for driving the speaker unit. 【0017】 In the electroacoustic converter, the first noise cancellation signal generation means generates a noise cancellation signal using a feedback (FB) method. 【0018】 The electroacoustic transducer according to the present invention further comprises: a second sound collection means installed in the front chamber of the housing facing the front side of the speaker unit, for collecting sound waves radiated from the speaker unit and noise components incident into the front chamber from outside the housing; a second noise cancellation signal generation means for generating a second noise cancellation signal that reduces the noise components collected by the second sound collection means; and a drive signal generation means for synthesizing the first noise cancellation signal and the second noise cancellation signal to generate a drive signal for driving the speaker unit. 【0019】 In this electroacoustic converter, the first and second noise cancellation signal generation means generate noise cancellation signals using a feedback (FB) method. 【0020】Furthermore, the electroacoustic transducer according to the present invention includes a third sound collection means installed facing the outside of the housing and for collecting noise signals incident from the outside of the housing, and a third noise cancellation signal generation means for generating a third noise cancellation signal that reduces the noise components collected by the third sound collection means. The electroacoustic transducer also includes a drive signal generation means that synthesizes the first noise cancellation signal and the third noise cancellation signal to generate a drive signal for driving the speaker unit. 【0021】 In this electroacoustic converter, the first noise cancellation signal generation means generates a noise cancellation signal using a feedback (FB) method, and the third noise cancellation signal generation means generates a noise cancellation signal using a feedforward (FF) method. 【0022】 Furthermore, the electroacoustic transducer according to the present invention further comprises: a third sound collection means installed facing the outside of the housing and for collecting noise signals incident from the outside of the housing; a third noise cancellation signal generation means for generating a third noise cancellation signal that reduces the noise components collected by the third sound collection means; and a drive signal generation means that synthesizes the first noise cancellation signal, the second noise cancellation signal, and the third noise cancellation signal to generate a drive signal for driving the speaker unit. 【0023】 In this electroacoustic converter, the first and second noise cancellation signal generation means generate noise cancellation signals using the FB method, and the third noise cancellation signal generation means generates noise cancellation signals using the FF method. 【0024】 In the housing constituting the electroacoustic transducer according to the present invention, the rear air chamber of the housing, in which the first sound-collecting means is installed, is open to the outside of the housing. 【0025】 Furthermore, the rear air chamber of the housing constituting the electroacoustic converter according to the present invention may be an acoustically shielded acoustic space. 【0026】Furthermore, the electroacoustic transducer according to the present invention may be provided with ear pads surrounding the front chamber of the housing, which faces the front side of the speaker unit. 【0027】 The electroacoustic transducer to which the present invention is applied achieves appropriate noise reduction functionality and enables the listening of audio with reduced noise components. Furthermore, this electroacoustic device makes it possible to reduce the degradation of sound quality of the audio being listened to. Moreover, the electroacoustic transducer to which the present invention is applied makes it possible to reduce noise in the audio being listened to while preventing the complexity of the configuration, which includes mechanisms for noise reduction. 【0028】 This is a schematic diagram showing a first embodiment in which the present invention is applied to headphones. This is a schematic diagram showing a second embodiment in which the present invention is applied to headphones. This is a schematic diagram showing a third embodiment in which the present invention is applied to headphones. This is a schematic diagram showing a fourth embodiment in which the present invention is applied to headphones. 【0029】 The present invention applies to electroacoustic transducers, including headphones and earphones. The following embodiments will be described using an example of its application to headphones worn on the head. 【0030】 The headphones to which the present invention is applied comprise a headband and a pair of headphone units connected to the left and right ends of the headband, respectively. Since the pair of headphone units have the same configuration on both the left and right sides, the following description will use one headphone unit as an example. 【0031】 (First Embodiment) A first embodiment of headphones to which the present invention is applied will be described. One headphone unit 1 constituting the headphones according to the first embodiment comprises a housing 2 and a speaker unit 3, as shown in Figure 1. The speaker unit 3 is mounted so as to be located inside the housing 2. At this time, the speaker unit 3 is mounted inside the housing 2 with the front side facing the diaphragm facing the front side of the housing 2. In addition, although not shown in detail, the speaker unit 3 has a frame supporting the diaphragm that is supported by a baffle plate 4 provided on the front side of the housing 2. 【0032】 Furthermore, an ear pad 5 is attached to the front side of the housing 2, which faces the diaphragm of the speaker unit 3. The ear pad 5 is attached to the front side of the baffle plate 4 so as to surround the diaphragm of the speaker unit 3. 【0033】 The headphone unit 1 according to this embodiment is worn by pressing the ear pads 5 against the side of the user's head. When the headphone unit 1 is worn on the head, the ear pads 5 form an acoustically closed space between the housing 2 and the side of the user's head H. This closed space is the front chamber 6 of the headphone unit 1. This front chamber 6 is an acoustic space into which sound waves from the speaker unit 3 are radiated. 【0034】 In this embodiment, the headphone unit 1 is located in the rear air chamber 7 of the housing 2, facing the rear side of the speaker unit 3, and a first microphone 8 constituting the first sound collection means is installed there. In this embodiment, the first microphone 8 is attached to a part of a well-known frame arranged inside the housing 2. The frame is not shown. The frame supports the diaphragm of the speaker unit 3 and also supports the drive unit including the magnetic circuit section 9 that vibrates the diaphragm. 【0035】 The first microphone 8, which is attached to a part of the frame located inside the housing, can be installed in any suitable position within the rear air chamber 7 of the housing 2, on the rear side of the speaker unit 3. 【0036】 The first microphone 8 then collects sound waves radiated from the speaker unit 3 to its rear side and noise components incident into the rear air chamber 7 from outside the housing 2, and outputs a noise signal. The noise components incident into the rear air chamber 7 are sound radiated from the external environment. 【0037】In this embodiment, the rear air chamber 7 of the housing 2, in which the first microphone 8 is installed, is open to the outside of the housing 2. That is, in this embodiment, a large opening is formed on the rear air chamber 7 side of the housing 2, and by placing a mesh-like grille or the like in this opening, external environmental noise is configured to directly enter the first microphone 8. 【0038】 Furthermore, the rear air chamber 7 of the housing 2 should be configured to be open so that noise components radiated from the external environment are incident on the first microphone 8 with an acoustically sufficient amplitude. 【0039】 The headphone unit 1 according to this embodiment includes a first noise cancellation signal generation circuit 10 which constitutes a first noise cancellation signal generation means to which a noise signal collected and output by a first microphone 8 is input. The first noise cancellation signal generation circuit 10 is composed of a digital filter circuit and generates a noise cancellation signal using the FB method. This first noise cancellation signal generation circuit 10 generates a noise cancellation signal by successively inverting the phase of the noise signal input from the first microphone 8. 【0040】 The headphone unit 1 according to this embodiment is equipped with an adder 11. The noise cancellation signal generated by the first noise cancellation signal generation circuit 10 is input to this adder 11. The playback audio signal output from the playback sound source 12 is also input to the adder 11. 【0041】 In Figure 1, which shows this embodiment, the playback sound source 12 is shown to be located inside the headphone unit 1. However, when configured as headphones worn on the head, the playback sound source 1 is located outside the headphones, and the playback audio signal is input to the adder 11 via wire or wireless connection. 【0042】 The adder 11 then combines the noise cancellation signal input from the noise cancellation signal generation circuit 10 with the playback audio signal input from the playback sound source 12 and outputs it as a drive signal that vibrates the diaphragm of the speaker unit 3. 【0043】In this embodiment, the adder 11 constitutes a driving signal generation means. The driving signal output from the adder 11 is input to a voice coil that constitutes a driving unit of the speaker unit 3, causing the diaphragm to vibrate and radiating reproduced sound from the diaphragm. The sound radiated from the speaker unit 3 includes an acoustic reproduction component due to the noise canceling signal generated in the noise canceling signal generation circuit 10. The acoustic reproduction component due to the noise canceling signal among the sounds acoustically reproduced and emitted by this speaker unit 3 and the noise component transmitted from the external environment incident on the front chamber 6 of the headphone unit 1 are acoustically synthesized, and the noise component is reduced at the noise canceling point Pc formed on the front chamber 6 side. 【0044】 The noise canceling point Pc is formed at a position close to the ear on the side of the listener's temporal bone where the headphone unit 1 is worn. At this noise canceling point Pc, since the noise component of the external environment incident on the front chamber 6 is reduced, the user of the headphones can reduce the noise component incident from the external environment and realize the listening of high-quality reproduced sound with sufficient suppression of the deterioration of the sound quality of the reproduced sound. 【0045】 In this embodiment, even when no reproduced audio signal is input from the reproduction sound source 12, it is possible to reduce the noise component transmitted from the external environment incident on the front chamber 6 of the headphone unit 1. Therefore, by using the headphones of this embodiment, it is possible to reduce the noise component incident on the ear from the external environment and realize a good acoustic environment. 【0046】 And in the headphones according to this embodiment, since the first microphone 8 is installed in the rear chamber 7 of the housing 2, it constitutes a conventionally used FB method noise reduction mechanism. Compared with the microphone installed on the front side of the speaker unit, the input level of the sound wave radiated from the speaker unit is reduced. Therefore, the occurrence of howling can be suppressed. 【0047】On the other hand, by being installed in the rear air chamber 7 of the housing 2, the first microphone 8 receives stronger sound waves radiated from the speaker unit compared to a microphone installed outside the cabinet or facing outside the cabinet that constitutes a noise reduction mechanism of the conventionally adopted FF method for collecting external environmental noise. Therefore, the first microphone 8 constituting the present embodiment can suppress performance degradation due to gain variation in the noise canceling signal generation system. 【0048】 Furthermore, the first microphone 8 constituting the noise reduction mechanism of the headphones according to the present embodiment can collect external environmental noise at a position closer to the auricle hole compared to a microphone installed outside the cabinet or facing outside the cabinet to constitute a noise reduction mechanism of the conventionally adopted FF method when the headphones are worn on the head. Therefore, the noise reduction mechanism according to the present embodiment can suppress the anisotropy of the noise canceling function and achieve good noise canceling. 【0049】 Furthermore, by being installed in the rear air chamber 7 of the housing 2, the first microphone 8 is less likely to be affected by disturbances caused by wind noise in the external environment. Therefore, stable generation of a noise canceling signal can be performed. 【0050】 In the present embodiment, the rear air chamber 7 of the housing 2 where the first microphone 8 is installed is open to the outside of the housing 2. Therefore, the passive sound insulation characteristics of the rear air chamber 7 are close to the open characteristics, and the first microphone 8 can collect external environmental noise with less alteration, enabling good noise canceling. 【0051】 In the present embodiment, although it is desirable that the rear air chamber 7 of the housing 2 is open to the outside, as long as the external environmental noise can be vibrationally transmitted to the first microphone 8 installed in the rear air chamber 7, it may have a sealed structure. 【0052】(Second Embodiment) Next, a second embodiment of headphones to which the present invention is applied will be described with reference to Figure 2. The headphones according to the second embodiment have a configuration in common with the headphones that constitute the first embodiment. Parts common to the first embodiment are denoted by the same reference numerals in Figure 2, and detailed descriptions are omitted. 【0053】 One headphone unit 20 constituting the headphones according to this embodiment includes a second microphone 21 in addition to the first microphone 8 provided in the headphone unit 1 according to the first embodiment. 【0054】 As shown in Figure 2, the second microphone 21 is installed in a front chamber 6, which is composed of a baffle plate 4 and an ear pad 5 attached to the front side of the baffle plate 4 so as to surround the diaphragm of the speaker unit 3. The second microphone 21 constitutes the second sound collection means of the present invention. 【0055】 In this embodiment, the second microphone 21 constitutes a noise reduction mechanism that reduces noise using the FB method. This second microphone 21 collects noise and reproduced sound. The noise collected by the second microphone 21 includes noise components from the external environment transmitted through the housing 2 and the baffle plate 4, and noise components from the external environment transmitted through the ear pad 5 as a vibration transmission member, or through the gap between the ear pad 5 and the listener's head. The reproduced sound is the reproduced sound produced by the noise-reduced sound signal radiated from the speaker unit 3. 【0056】 The second microphone 21 is positioned at the music listening position of the listener wearing headphones, and is a noise cancellation point Pc, which is an acoustic synthesis position where the noise and the reproduced sound with the noise reduction audio signal are combined. 【0057】The headphone unit 20 according to this embodiment is provided with a second noise cancellation signal generation circuit 22 which constitutes a second noise cancellation signal generation means. The second cancellation signal generation circuit 22 receives a noise signal generated from noise components incident from the external environment collected by the second microphone 21 and a playback audio signal generated from the playback sound radiated from the speaker unit 3. 【0058】 The second noise cancellation signal generation circuit 22 is composed of a digital filter circuit and generates a noise cancellation signal using the FB method. The second noise cancellation signal generation circuit 22 generates a second noise cancellation signal by successively inverting the phase of the noise signal input from the second microphone 21. 【0059】 The second noise cancellation signal is input to the adder 23. The adder 23 in this embodiment receives the first noise cancellation signal generated by the first noise cancellation signal generation circuit 10 described in the first embodiment. Furthermore, the playback audio signal output from the playback sound source 12 is also input to the adder 23. 【0060】 The adder 23 then combines the first noise cancellation signal generated by the first noise cancellation signal generation circuit 10, the second noise cancellation signal generated by the second noise cancellation signal generation circuit 22, and the playback audio signal input from the playback sound source 12, and outputs it as a drive signal that vibrates the diaphragm of the speaker unit 3. 【0061】 The drive signal output from the adder 23 is input to the voice coil that constitutes the drive unit of the speaker unit 3, causing the diaphragm to vibrate and radiate sound from the diaphragm. The sound radiated from the speaker unit 3 includes an acoustic reproduction component from the noise cancellation signal generated by the first noise cancellation signal generation circuit 10 and an acoustic reproduction component from the second noise cancellation signal generated by the second noise cancellation signal generation circuit 22. 【0062】The sound reproduced and emitted by the speaker unit 3, specifically the sound reproduction component due to the first noise cancellation signal generated by the first noise cancellation signal generation circuit 10, and the sound reproduction component due to the second noise cancellation signal generated by the second noise cancellation signal generation circuit 22, are radiated into the front chamber 6 of the headphone unit 1. 【0063】 The reproduced sound from the first noise cancellation signal is acoustically combined with noise components transmitted from the external environment that enter the front chamber 6 of the headphone unit 1. As a result, the noise components transmitted from the external environment are reduced at the noise cancellation point Pc formed on the front chamber 6 side. 【0064】 Furthermore, the reproduced sound from the second noise cancellation signal is acoustically synthesized from noise components transmitted from the external environment incident on the front chamber 6 of the headphone unit 1 and noise components transmitted via the ear pads 5. As a result, the noise components are reduced at the noise cancellation point Pc formed on the front chamber 6 side. 【0065】 The headphones according to this embodiment reduce noise components that enter the ear through the rear chamber from the external environment, as achieved by the first embodiment described above. Furthermore, by using an FB-type microphone configuration, it is possible to reduce noise components that enter the front chamber 6 using the ear pad 5 as a transmission member. This reduces various noise components that enter the headphones, resulting in the listening of even higher quality reproduced sound. 【0066】 In this embodiment, even when no playback audio signal is input from the playback sound source 12, it is possible to reduce noise components transmitted from the external environment that enter the front chamber 6 of the headphone unit 1. Therefore, by using the headphones of this embodiment, it is possible to reduce noise components that enter the ear from the external environment and realize a good acoustic environment. 【0067】In this embodiment as well, it is preferable that the rear air chamber 7 of the housing 2 be open to the outside, but it may also be a sealed structure as long as it is structured in such a way that external environmental noise can be transmitted as vibration to the first microphone 8 installed inside the rear air chamber 7. 【0068】 (Third Embodiment) Next, a third embodiment of headphones to which the present invention is applied will be described with reference to Figure 3. The headphones according to the third embodiment have a configuration in common with the headphones that constitute the first embodiment. Parts common with the first embodiment are denoted by the same reference numerals in Figure 3, and detailed descriptions are omitted. 【0069】 One headphone unit 30 constituting the headphones according to this embodiment is provided with a third microphone 31 constituting a third sound collection means, in addition to the first microphone 8 provided in the headphone unit 1 according to the first embodiment. The third microphone 31 acoustically and directly collects noise components incident from the external environment of the housing 2. In this embodiment, the third microphone 31 is located on the outer circumference side of the rear air chamber 7 of the housing 2, and its sound collection surface is set facing the outside of the housing 2. 【0070】 The headphones according to this embodiment include a third noise cancellation signal generation circuit 32 that generates a noise cancellation signal using the FF method. Noise components collected by the third microphone 31 are input to the third noise cancellation signal generation circuit 32. The third noise cancellation signal generation circuit 32 analyzes the noise collected by the third microphone 31, predicts the changes in the noise until it reaches the listener's playback sound listening point, and based on this prediction result, applies appropriate filtering processing to the noise collected by the third microphone 31 to generate a third noise cancellation signal that is out of phase with the noise. 【0071】 The third noise cancellation signal is input to the adder 33. In this embodiment, the adder 33 receives the first noise cancellation signal generated by the first noise cancellation signal generation circuit 10 described in the first embodiment. Furthermore, the adder 33 receives the playback audio signal output from the playback sound source 12. 【0072】 The adder 33 then combines the first noise cancellation signal generated by the first noise cancellation signal generation circuit 10, the third noise cancellation signal generated by the third noise cancellation signal generation circuit 32, and the playback audio signal input from the playback sound source 12, and outputs it as a drive signal that vibrates the diaphragm of the speaker unit 3. 【0073】 The drive signal output from the adder 33 is input to the voice coil that constitutes the drive unit of the speaker unit 3, causing the diaphragm to vibrate and radiate sound from the diaphragm. The sound radiated from the speaker unit 3 includes an acoustic reproduction component from the first noise cancellation signal generated by the first noise cancellation signal generation circuit 10 and an acoustic reproduction component from the third noise cancellation signal generated by the third noise cancellation signal generation circuit 32. 【0074】 The sound reproduced and emitted by the speaker unit 3, including the sound reproduction component due to the first noise cancellation signal generated by the first noise cancellation signal generation circuit 10 and the sound reproduction component due to the third noise cancellation signal generated by the third noise cancellation signal generation circuit 32, are radiated into the front chamber 6 of the headphone unit 1. 【0075】 The reproduced sound from the first noise cancellation signal is acoustically combined with noise components transmitted from the external environment that enter the front chamber 6 of the headphone unit 1, and the noise components transmitted from the external environment are reduced at the noise cancellation point Pc formed on the front chamber 6 side. 【0076】 Furthermore, the reproduced sound from the third noise cancellation signal is acoustically synthesized with noise components radiated from the external environment, and the noise components from the external environment are reduced at the noise cancellation point Pc formed on the front air chamber 6 side. 【0077】The headphones according to this embodiment reduce noise components that enter the ear through the rear chamber from the external environment, as achieved by the first embodiment described above. Furthermore, noise components radiated from the external environment in which the headphones are used can be reduced using an FF-type microphone configuration, thereby reducing various noise components that enter the headphones and enabling the listening of even higher quality reproduced sound. 【0078】 In this embodiment, even when no playback audio signal is input from the playback sound source 12, it is possible to reduce noise components transmitted from the external environment that enter the front chamber 6 of the headphone unit 1. Therefore, by using the headphones of this embodiment, it is possible to reduce noise components that enter the ear from the external environment and realize a good acoustic environment. 【0079】 In this embodiment as well, it is preferable that the rear air chamber 7 of the housing 2 be open to the outside, but it may also be a sealed structure as long as it is structured in such a way that external environmental noise can be transmitted as vibration to the first microphone 8 installed inside the rear air chamber 7. 【0080】 (Fourth Embodiment) Next, a fourth embodiment of headphones to which the present invention is applied will be described with reference to Figure 4. The headphones according to the fourth embodiment have a configuration in common with the headphones that constitute the second and third embodiments, respectively. Parts common with the second and third embodiments are denoted by the same reference numerals in Figure 4, and detailed descriptions are omitted. 【0081】 One headphone unit 40 constituting the headphones according to this embodiment includes, in addition to the first microphone 8 provided by the headphone unit 1 according to the first embodiment described above, a second microphone 21 provided by the headphone unit 20 of the headphones according to the second embodiment, and a third microphone 31 provided by the headphone unit 30 of the headphones according to the third embodiment. 【0082】In this embodiment, the adder 43, which receives the playback audio signal output from the playback sound source 12, receives the first noise cancellation signal generated by the first noise cancellation signal generation circuit 10, the second noise cancellation signal generated by the second noise cancellation signal generation circuit 22, and the third noise cancellation signal generated by the third noise cancellation signal generation circuit 32. 【0083】 The adder 43 then combines the first noise cancellation signal generated by the first noise cancellation signal generation circuit 10, the second noise cancellation signal generated by the second noise cancellation signal generation circuit 22, the third noise cancellation signal generated by the third cancellation signal generation circuit 32, and the playback audio signal input from the playback sound source 12, and outputs it as a drive signal that vibrates the diaphragm of the speaker unit 3. 【0084】 The drive signal output from the adder 43 is input to the voice coil that constitutes the drive unit of the speaker unit 3, causing the diaphragm to vibrate and radiate sound from the diaphragm. The sound radiated from the speaker unit 3 includes an acoustic reproduction component from the first noise cancellation signal generated by the first noise cancellation signal generation circuit 10, an acoustic reproduction component from the second noise cancellation signal generated by the second noise cancellation signal generation circuit 22, and an acoustic reproduction component from the noise cancellation signal generated by the third noise cancellation signal generation circuit 32. 【0085】 The sound reproduced and emitted by the speaker unit 40 according to this embodiment, including the sound reproduction component due to the first noise cancellation signal, the sound reproduction component due to the second noise cancellation signal, and the sound reproduction component due to the third noise cancellation signal, are radiated into the front chamber 6 of the headphone unit 1. 【0086】 The reproduced sound from the first noise cancellation signal is acoustically combined with noise components transmitted from the external environment that enter the front chamber 6 of the headphone unit 1, and the noise components transmitted from the external environment are reduced at the noise cancellation point Pc formed on the front chamber 6 side. 【0087】The reproduced sound from the second noise cancellation signal is then combined with the noise components transmitted to the front chamber 6 of the headphone unit 1, and at the noise cancellation point Pc formed on the front chamber 6 side, an FB-type microphone configuration is used to reduce the noise components transmitted from the external environment. 【0088】 Furthermore, the reproduced sound from the third noise cancellation signal is acoustically synthesized with noise components radiated from the external environment, and at the noise cancellation point Pc formed on the front air chamber 6 side, the noise components from the external environment are reduced using an FF type microphone configuration. 【0089】 The headphones according to this embodiment reduce noise components that enter the ear through the rear chamber from the external environment, as realized by the first embodiment described above. In addition, by using an FB-type microphone configuration to further reduce noise components, and further by using an FF-type microphone configuration to further reduce noise components, a variety of noise components enter the headphones are reduced, resulting in the listening of even higher quality reproduced sound. 【0090】 In this embodiment, even when no playback audio signal is input from the playback sound source 12, it is possible to reduce noise components transmitted from the external environment that enter the front chamber 6 of the headphone unit 1. Therefore, by using the headphones of this embodiment, it is possible to reduce noise components that enter the ear from the external environment and realize a good acoustic environment. 【0091】 In this embodiment as well, it is preferable that the rear air chamber 7 of the housing 2 be open to the outside, but it may also be a sealed structure as long as it is structured in such a way that external environmental noise can be transmitted as vibration to the first microphone 8 installed inside the rear air chamber 7. 【0092】1 Headphone unit, 2 Housing, 3 Speaker unit, 5 Ear pads, 6 Front chamber, 7 Rear chamber, 8 First microphone, 10 First noise cancellation signal generation circuit, 11 Adder, 20 Headphone unit, 21 Second microphone, 22 Second noise cancellation signal generation circuit, 23 Adder, 30 Headphone unit, 31 Third microphone, 32 Third noise cancellation signal generation circuit, 33 Adder
Claims
1. An electroacoustic transducer comprising: a housing; a speaker unit mounted within the housing; a first sound collection means installed in the rear chamber of the housing facing the rear side of the speaker unit, for collecting sound waves radiated from the speaker unit and noise components incident into the rear chamber from outside the housing; a first noise cancellation signal generation means for generating a first noise cancellation signal to reduce the noise components collected by the first sound collection means; and a drive signal generation means for generating a drive signal to drive the speaker unit.
2. The electroacoustic converter according to claim 1, characterized in that the drive signal generation means synthesizes the playback audio signal supplied from the playback sound source with the first noise cancellation signal.
3. The electroacoustic converter according to claim 1, characterized in that the first noise cancellation signal generation means generates a noise cancellation signal in a feedback manner.
4. The electroacoustic transducer according to claim 1, comprising: a second sound collection means installed in the front chamber of the housing facing the front side of the speaker unit, for collecting sound waves radiated from the speaker unit and noise components incident into the front chamber from outside the housing; a second noise cancellation signal generation means for generating a second noise cancellation signal that reduces the noise components collected by the second sound collection means; and a drive signal generation means that synthesizes the first noise cancellation signal and the second noise cancellation signal to generate a drive signal for driving the speaker unit.
5. The electroacoustic converter according to claim 4, characterized in that the first and second noise cancellation signal generating means generate a noise cancellation signal in a feedback manner.
6. The electroacoustic converter according to claim 1, comprising: a third sound collection means installed facing the outside of the housing and for collecting noise signals incident from the outside of the housing; a third noise cancellation signal generation means for generating a third noise cancellation signal that reduces the noise components collected by the third sound collection means; and a drive signal generation means that synthesizes the first noise cancellation signal and the third noise cancellation signal to generate a drive signal for driving the speaker unit.
7. The electroacoustic converter according to claim 6, characterized in that the first noise cancellation signal generation means generates a noise cancellation signal in a feedback manner, and the third noise cancellation signal generation means generates a noise cancellation signal in a feedforward manner.
8. The electroacoustic transducer according to claim 4, comprising: a third sound collection means installed facing the outside of the housing for collecting noise signals incident from the outside of the housing; a third noise cancellation signal generation means for generating a third noise cancellation signal that reduces the noise components collected by the third sound collection means; and a drive signal generation means that synthesizes the first noise cancellation signal, the second noise cancellation signal, and the third noise cancellation signal to generate a drive signal for driving the speaker unit.
9. The electroacoustic converter according to claim 8, characterized in that the first and second noise cancellation signal generating means generate a noise cancellation signal in a feedback manner, and the third noise cancellation signal generating means generates a noise cancellation signal in a feedforward manner.
10. The electroacoustic transducer according to any one of claims 1 to 9, characterized in that the rear air chamber of the housing in which the first sound collection means is installed is open to the outside of the housing.
11. The electroacoustic transducer according to any one of claims 1 to 9, characterized in that the rear air chamber of the housing is an acoustically shielded acoustic space.
12. The electroacoustic transducer according to any one of claims 1 to 9, characterized in that ear pads are provided surrounding the front chamber of the housing that the front side of the speaker unit faces.