JP5364098B2 - Noise canceling headphones - Google Patents

Noise canceling headphones Download PDF

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JP5364098B2
JP5364098B2 JP2010528680A JP2010528680A JP5364098B2 JP 5364098 B2 JP5364098 B2 JP 5364098B2 JP 2010528680 A JP2010528680 A JP 2010528680A JP 2010528680 A JP2010528680 A JP 2010528680A JP 5364098 B2 JP5364098 B2 JP 5364098B2
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noise
signal
circuit
frequency
cutoff frequency
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JPWO2010029796A1 (en
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富至 木村
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Audio Technica KK
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
    • H04R1/1083—Reduction of ambient noise
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1781—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions
    • G10K11/17821—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions characterised by the analysis of the input signals only
    • G10K11/17823—Reference signals, e.g. ambient acoustic environment
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1785—Methods, e.g. algorithms; Devices
    • G10K11/17853—Methods, e.g. algorithms; Devices of the filter
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1787—General system configurations
    • G10K11/17873—General system configurations using a reference signal without an error signal, e.g. pure feedforward
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1787—General system configurations
    • G10K11/17885—General system configurations additionally using a desired external signal, e.g. pass-through audio such as music or speech
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/10—Applications
    • G10K2210/108—Communication systems, e.g. where useful sound is kept and noise is cancelled
    • G10K2210/1081—Earphones, e.g. for telephones, ear protectors or headsets

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Audiology, Speech & Language Pathology (AREA)
  • General Health & Medical Sciences (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Headphones And Earphones (AREA)

Description

本発明は、周囲の騒音（以下、「環境騒音」という）を打ち消して音楽のみを聞くことができるノイズキャンセルヘッドホンであって、特に、騒音の特性に応じてキャンセル特性を変化させることができるノイズキャンセルヘッドホンに関するものである。   The present invention is a noise canceling headphone capable of canceling ambient noise (hereinafter referred to as “environmental noise”) and listening to only music, and in particular, noise capable of changing the canceling characteristic in accordance with the characteristic of noise. It relates to cancellation headphones.

環境騒音をキャンセル音によって打ち消しつつ、再生された音楽を聴くことができるノイズキャンセルヘッドホンは、ヘッドホン筐体に取り付けられたマイクロホンユニットによって集音される環境騒音を電気信号に変換して、この騒音信号を元に、ヘッドホン筐体を通過して利用者の耳に聞こえる騒音を打ち消すキャンセル音を生成し、このキャンセル音と再生する音楽をともにヘッドホンスピーカユニットから出力することで環境騒音が打ち消された状態で音楽を聴くことができるように構成されている。
従って、環境騒音が利用者の周囲の状況を知らせる音（例えばサイレンやクラクションなど）であっても、これを打ち消すことになるので、このような周囲の状況を把握するのに必要な音によってもたらされる利用者の安全が阻害される原因となる。そこで、ノイズに含まれる周囲の状況を知らせる音の中から「利用者にとって興味深い音」を選択的に分離し、この「利用者にとって興味深い音」に対してはキャンセル信号を生成せず、それ以外の音に対してはキャンセル信号を生成することで、利用者が安全に使用することができるノイズキャンセルヘッドホンが知られている（例えば特許文献１参照）。
特開２００４−５２６３７５号公報 Noise canceling headphones that can listen to the reproduced music while canceling the environmental noise with the canceling sound convert the environmental noise collected by the microphone unit attached to the headphone housing into an electrical signal. Based on the above, a cancellation sound is generated that cancels the noise that can be heard by the user's ears through the headphone housing. Is configured to listen to music.
Therefore, even if the environmental noise is a sound that informs the user's surroundings (for example, sirens or horns), it cancels out the noise. It will cause the safety of users to be disturbed. Therefore, “sound interesting to the user” is selectively separated from the sounds informing the surrounding situation included in the noise, and no cancellation signal is generated for this “sound interesting to the user”. A noise canceling headphone that can be used safely by a user by generating a cancel signal for the sound is known (see, for example, Patent Document 1).
JP 2004-526375 A

また、ノイズキャンセルヘッドホンは屋外や電車の中などにおいて環境騒音に左右されることなく静かな環境で音楽を楽しむことに用いるほか、裸の耳でそのまま聴いていては難聴になってしまうような大音量の騒音環境下（例えば、カーレース場のピット、飛行機の整備場、工事現場など）において、聴覚を保護する防音具（イヤーマフ）として用いることもできる。この場合、主に高音域を中心にキャンセルするように動作をするものが用いられる。   Noise-canceling headphones can be used to enjoy music in a quiet environment without being affected by environmental noise outdoors or in trains, and it can be difficult to hear if you listen with bare ears. It can also be used as a soundproofing device (ear muff) for protecting hearing in a loud noise environment (for example, car race pits, airplane maintenance, construction sites, etc.). In this case, what operates mainly to cancel mainly in the high sound range is used.

従来のノイズキャンセルヘッドホンは、環境騒音がこれをキャンセルする必要がないくらい充分に小さいときであっても、キャンセル音が生成されて出力される。そうすると、キャンセル信号用のアンプから発せられる残留ノイズによる音が環境騒音よりも大きく聞こえてしまい、聴いている音楽の音質を変化させてしまうことがある。同様に、環境騒音がこれをキャンセルする必要がないくらい小さいときであっても、マイクユニットによって集音されると、その環境騒音を打ち消すキャンセル音が出力される。このようなキャンセル音は環境騒音の高音域まで打ち消すキャンセル信号となるので、利用者においては周囲の状況を音で把握しにくくなり事故に遭遇することがあり得る。
本発明は、上記課題を鑑みてなされたものであって、環境騒音レベルの特性に応じてキャンセル特性を変化させることができるノイズキャンセルヘッドホンであって、環境騒音が使用者の設定したレベル以下になったとき、雑音抑制用ローパスフィルター回路を有効にし、また、環境騒音が大きく使用者の設定したレベル以上になったとき、雑音抑制用ローパスフィルター回路を無効にすることで、低騒音時にはノイズキャンセル回路から発生する残留ノイズを抑制し、利用者の安全を向上させた低域ノイズを中心とするノイズキャンセルをすることができるノイズキャンセルヘッドホンを提供することを目的とする。Conventional noise-canceling headphones generate and output a cancellation sound even when the environmental noise is sufficiently low that it is not necessary to cancel it. Then, the sound due to the residual noise emitted from the cancel signal amplifier may be heard louder than the environmental noise, and the sound quality of the music being listened to may be changed. Similarly, even when the environmental noise is so small that it is not necessary to cancel it, when the sound is collected by the microphone unit, a canceling sound that cancels the environmental noise is output. Since such a canceling sound becomes a canceling signal that cancels out to the high range of the environmental noise, it is difficult for the user to grasp the surrounding situation with the sound and may encounter an accident.
The present invention has been made in view of the above problems, and is a noise canceling headphone capable of changing a canceling characteristic in accordance with a characteristic of an environmental noise level, wherein the environmental noise is below a level set by a user. When the noise becomes low, the noise suppression low-pass filter circuit is enabled, and when the environmental noise is significantly higher than the level set by the user, the noise suppression low-pass filter circuit is disabled to cancel the noise at low noise. An object of the present invention is to provide a noise-canceling headphone that can suppress residual noise generated from a circuit and perform noise cancellation centering on low-frequency noise that improves user safety.

本発明は、ノイズキャンセルヘッドホンに関するものであって、環境騒音を電気信号に変換するマイクロホンと、上記マイクロホンで変換される騒音信号を打ち消すキャンセル信号を生成するキャンセル信号生成手段と、オーディオ信号と上記キャンセル信号により駆動されるスピーカと、上記キャンセル信号の低域成分を濾過する残留ノイズ抑制用ローパスフィルター回路と、上記騒音信号の検出レベルの基準となる電圧を生成する基準電圧回路と、上記騒音信号と上記基準となる電圧とを比較して上記騒音信号のレベルを検出し、検出結果を示す制御信号を出力する判定回路と、上記制御信号に応じて上記残留ノイズ抑制用ローパスフィルター回路の遮断周波数を可変させる遮断周波数制御回路と、を有することを最も主要な特徴とする。 The present invention relates to a noise canceling headphones, a microphone for converting environmental noise into an electric signal, and cancellation signal generation means for generating an erasing to Cancel signal beat noise signal converted by the microphone, an audio signal and a speaker which is driven by the cancel signal, a low pass filter circuit for residual noise suppression filtering a low frequency component of the canceling signal, and a reference voltage circuit for generating a voltage as a reference of the detection level of the noise signal, the by comparing the voltage to be noise signal and the reference to detect the level of the noise signal, and a judging circuit for outputting a control signal indicating the result detect, a low-pass filter circuit for the residual noise suppression according to the control signal the most important feature to have a cutoff frequency control circuit for varying the cut-off frequency of the

本発明によれば、環境騒音が小さく、使用者の設定したレベル以下になったときは、残留ノイズ抑制用ローパスフィルター回路を有効にすることにより、ノイズキャンセル回路から発生する残留ノイズを抑制することができる。環境騒音が大きく使用者の設定したレベル以上になったときは、ローパスフィルター回路を無効にし、中・高音域にまでノイズキャンセル信号を出力することができるようにする。これによって、低騒音時には利用者の安全を向上させ低域ノイズを中心とするノイズキャンセルをすることができ、高騒音時には高いキャンセル効果を発揮するノイズキャンセルヘッドホンを得ることができる。
また本発明によれば、使用者が設定したノイズレベルや難聴になる可能性のある大きなノイズレベルのときにのみ本来のノイズキャンセル機能を動作させ、ノイズレベルが低いときや特定の周波数しか含まないノイズのときにはノイズキャンセルのキャンセル周波数特性を選んでノイズをキャンセルすることができ、しかも周囲のノイズが小さい時に不要なアンプの高域ノイズを抑制し音楽を高音質で聴くことが出来るようになる。
また、環境騒音が小さいときには、話し声など周囲の中・高音は聞こえるため、屋外で事故に遭う危険性も減らすことが出来る。使用者はボリュームや切替えスイッチで自由にノイズキャンセル機能の動作レベルやキャンセル周波数をコントロールでき使用環境に合わせることが出来る。
また、基準動作レベルを、難聴になる恐れがあるほどの高い音圧レベルに合わせておけば、騒音レベルが上記基準動作レベル以上になると、中・高音域にまでノイズキャンセル効果が及ぶため、使用者が難聴になることを防止することもできる。According to the present invention, when the environmental noise is small and becomes lower than the level set by the user, the residual noise suppression low pass filter circuit is enabled to suppress the residual noise generated from the noise cancellation circuit. Can do. When the environmental noise is much higher than the level set by the user, the low-pass filter circuit is disabled so that a noise cancellation signal can be output even in the middle / high range. Thus, it is possible to improve the safety of the user when noise is low and cancel noise centering on low-frequency noise, and to obtain a noise-canceling headphone that exhibits a high canceling effect when noise is high.
Further, according to the present invention, the original noise cancellation function is operated only when the noise level set by the user or a large noise level that may cause hearing loss is included, and only a specific frequency is included when the noise level is low. In the case of noise, it is possible to cancel the noise by selecting a cancel frequency characteristic of noise cancellation. Further, when the surrounding noise is small, unnecessary high frequency noise of the amplifier is suppressed and music can be listened to with high sound quality.
Also, when the environmental noise is low, you can hear the middle and high sounds around you, such as talking voice, so you can reduce the risk of accidents outdoors. The user can freely control the operation level and cancellation frequency of the noise cancellation function with the volume and changeover switch, and can adjust to the usage environment.
In addition, if the reference operation level is set to a sound pressure level that is high enough to cause hearing loss, if the noise level exceeds the above-mentioned reference operation level, the noise canceling effect extends to the middle and high sound ranges. It is also possible to prevent a person from hearing loss.

第１図は、本発明にかかるノイズキャンセルヘッドホンの一実施例を示す機能ブロック図である。
第２図は、本発明にかかるノイズキャンセルヘッドホンの別の実施例を示す機能ブロック図である。
第３図は、本発明にかかるノイズキャンセルヘッドホンのさらに別の実施例を示す機能ブロック図である。
第４図は、本発明にかかるノイズキャンセルヘッドホンのさらに別の実施例を示す機能ブロック図である。
第５図は、本発明にかかるノイズキャンセルヘッドホンのさらに別の実施例を示す機能ブロック図である。FIG. 1 is a functional block diagram showing an embodiment of a noise cancellation headphone according to the present invention.
FIG. 2 is a functional block diagram showing another embodiment of the noise cancellation headphones according to the present invention.
FIG. 3 is a functional block diagram showing still another embodiment of the noise canceling headphones according to the present invention.
FIG. 4 is a functional block diagram showing still another embodiment of the noise cancellation headphones according to the present invention.
FIG. 5 is a functional block diagram showing still another embodiment of the noise canceling headphones according to the present invention.

１１ マイクユニット
１３ ノイズキャンセル信号生成回路
１４ スイッチ
１５ 残留ノイズ抑制用ローパスフィルター
１６ 外部ノイズレベル検出回路
１７ 基準電圧回路
１８ ヘッドホンアンプ
２０ 遮断周波数制御回路
２１ 基準電圧調整回路
２２ 遮断周波数調整回路
２３ 周波数弁別回路DESCRIPTION OF SYMBOLS 11 Microphone unit 13 Noise cancellation signal generation circuit 14 Switch 15 Residual noise suppression low pass filter 16 External noise level detection circuit 17 Reference voltage circuit 18 Headphone amplifier 20 Cutoff frequency control circuit 21 Reference voltage adjustment circuit 22 Cutoff frequency adjustment circuit 23 Frequency discrimination circuit

以下、本発明に係るノイズキャンセルヘッドホンの実施例について図面を参照しながら説明する。   Embodiments of a noise canceling headphone according to the present invention will be described below with reference to the drawings.

図１において、ノイズキャンセルヘッドホン１は、マイクユニット１１と、マイクアンプ１２と、ノイズキャンセル信号生成回路１３と、スイッチ１４と、残留ノイズ抑制用ローパスフィルター（ＬＰＦ）１５と、ヘッドホンアンプ１８と、ヘッドホンスピーカ１９と、外部ノイズレベル検出回路１６と、基準電圧回路１７と、を有してなる。
マイクユニット１１は、環境騒音である外部ノイズ３０を集音して電気信号に変換し、これを騒音信号として出力する。マイクアンプ１２は、マイクユニット１１から出力される騒音信号を所定レベルに増幅して出力する。ノイズキャンセル信号生成回路１３は、マイクアンプ１２から出力される騒音信号を元に、ヘッドホン筐体を通過して利用者の耳に入ろうとする環境騒音を打ち消すキャンセル信号を生成して出力する。
残留ノイズ抑制用ＬＰＦ１５は、キャンセル信号の高域を遮断して低域を通過させるフィルター回路であって、残留ノイズ抑制用ＬＰＦ１５の動作を有効にすることにより、マイクユニット１１、マイクアンプ１２、ノイズキャンセル信号生成回路１３によって発生する残留ノイズを低減することができる。
ヘッドホンアンプ１８は、ノイズキャンセル信号生成回路１３の出力信号によってヘッドホンスピーカ１９を駆動するアンプである。ただし、スイッチ１４の開閉によって、残留ノイズ抑制用ＬＰＦ１５を通ったノイズキャンセル信号生成回路１３の出力信号、または、残留ノイズ抑制用ＬＰＦ１５をバイパスしたノイズキャンセル信号生成回路１３の出力信号によってヘッドホンスピーカ１９を駆動する。ヘッドホンスピーカ１９は、ヘッドホンアンプ１８の出力信号によって駆動され、環境騒音をキャンセルするための音波を出力する。
外部ノイズレベル検出回路１６は、ヘッドホンアンプ１８が出力するキャンセル信号のレベルを検出し、その結果を制御信号として出力する回路であって、キャンセル信号を予め規定する基準電圧と比較することで、騒音信号のレベルを検出する。外部ノイズレベル検出回路１６は、環境騒音のレベル検出ができればよいので、マイクアンプ１２、ノイズキャンセル信号生成回路１３、ヘッドホンアンプ１８のいずれから得てもよい。基準電圧回路１７は、外部ノイズレベル検出回路１６が騒音信号のレベル検出に用いる基準電圧を生成する回路で、この基準電圧は外部ノイズレベル検出回路１６に供給される。
外部ノイズレベル検出回路１６は、基準電圧と騒音信号レベルとを比較することで騒音信号のレベルを検出し、騒音信号のレベルが基準電圧よりも高ければ（外部ノイズ３０が所定の音量よりも大きければ）、スイッチ１４を閉じるための制御信号を出力する。騒音信号のレベルが基準電圧よりも低ければ（外部ノイズ３０が所定の音量よりも小さければ）、スイッチ１４を開放するための制御信号を出力する。スイッチ１４は、外部ノイズレベル検出回路１６からの制御信号によって開閉し、ノイズキャンセル信号生成回路１３の出力信号であるキャンセル信号を、残留ノイズ抑制用ＬＰＦ１５を通してヘッドホンアンプ１８に供給するか、または、残留ノイズ抑制用ＬＰＦ１５をバイパスしてヘッドホンアンプ１８に供給するかを選択するスイッチである。
上記ノイズキャンセルヘッドホン１は、左右一対で構成される図示しないヘッドホン筐体に収められた状態で利用可能になる。ヘッドホン筐体は上記のノイズキャンセルヘッドホン１を両側の筐体に収めてもいいし、片側のみに収めてもよい。両側の筐体に収められるときは、楽音信号入力用のコードを、左右の筐体に収められたノイズキャンセルヘッドホン１にそれぞれ接続し、例えば、ヘッドホンアンプ１８の前段にミックス回路を設けて、ここでキャンセル信号と混合しヘッドホンアンプ１８によってヘッドホンスピーカ１９からキャンセル信号と音楽信号を出力するように構成すればよい。
片側の筐体に収められて左右のヘッドホン筐体がヘッドバンドで結合されている形式のヘッドホンの場合、片方のヘッドホン筐体から他方のヘッドホン筐体に楽音信号が伝達される配線を上記ヘッドバンドに埋め込んでもよい。また、駆動用の上記電池は片方のヘッドホン筐体にのみ装填するように構成すればよい。
上記の構成を有するノイズキャンセルヘッドホン１によれば、外部ノイズ３０の音量が小さいときは、残留ノイズ抑制用ＬＰＦ１５によってマイクアンプ１２等の残留ノイズを除去したキャンセル信号を出力し、静かな環境で聞いている音楽を残留ノイズによって変化させることなく、高音質のノイズキャンセルヘッドホンとして用いることができる。
また、外部ノイズ３０の音量が大きいときは、スイッチ１４によって残留ノイズ抑制用ＬＰＦ１５をバイパスし、ノイズキャンセル信号生成回路１３で生成されるキャンセル信号をそのまま、したがって、中高音域もそのまま出力することで、より広い周波数帯域の環境騒音を打ち消すことができる。
以上説明した実施例では、残留ノイズ抑制用ＬＰＦ１５がノイズキャンセル信号生成回路１３の後段に備えられている。しかし、本発明に係るノイズキャンセルヘッドホンは、この例に限ることなく、残留ノイズ抑制用ＬＰＦ１５の位置が、マイクアンプ１２の後段であってもよいし、ヘッドホンアンプ１８の後段であってもよい。残留ノイズ抑制用ＬＰＦ１５は、残留ノイズが耳障りにならないように、その高域を除去する目的で用いている。残留ノイズの高域が除去されると同様に、キャンセル信号の高域も除去されるので、その分、キャンセル効果は低くなるが、上記のように残留ノイズ抑制用ＬＰＦ１５を備える位置を調整することで、残留ノイズを低減しつつ、キャンセル効果を得ることができる最適なノイズキャンセルヘッドホンを得ることができる。In FIG. 1, a noise canceling headphone 1 includes a microphone unit 11, a microphone amplifier 12, a noise canceling signal generation circuit 13, a switch 14, a residual noise suppressing low-pass filter (LPF) 15, a headphone amplifier 18, and a headphone. A speaker 19, an external noise level detection circuit 16, and a reference voltage circuit 17 are provided.
The microphone unit 11 collects external noise 30 that is environmental noise, converts it into an electrical signal, and outputs this as a noise signal. The microphone amplifier 12 amplifies the noise signal output from the microphone unit 11 to a predetermined level and outputs it. Based on the noise signal output from the microphone amplifier 12, the noise cancellation signal generation circuit 13 generates and outputs a cancellation signal that cancels environmental noise that passes through the headphone housing and enters the user's ear.
The residual noise suppression LPF 15 is a filter circuit that blocks the high frequency band of the cancel signal and passes the low frequency band. By enabling the operation of the residual noise suppression LPF 15, the microphone unit 11, microphone amplifier 12, noise Residual noise generated by the cancel signal generation circuit 13 can be reduced.
The headphone amplifier 18 is an amplifier that drives the headphone speaker 19 by the output signal of the noise cancellation signal generation circuit 13. However, when the switch 14 is opened / closed, the headphone speaker 19 is turned on by the output signal of the noise cancellation signal generation circuit 13 passing through the residual noise suppression LPF 15 or the output signal of the noise cancellation signal generation circuit 13 bypassing the residual noise suppression LPF 15. To drive. The headphone speaker 19 is driven by the output signal of the headphone amplifier 18 and outputs a sound wave for canceling environmental noise.
The external noise level detection circuit 16 is a circuit that detects the level of the cancellation signal output from the headphone amplifier 18 and outputs the result as a control signal. The external noise level detection circuit 16 compares the cancellation signal with a predetermined reference voltage, thereby reducing noise. Detect the signal level. The external noise level detection circuit 16 may be obtained from any of the microphone amplifier 12, the noise cancellation signal generation circuit 13, and the headphone amplifier 18 as long as it can detect the level of environmental noise. The reference voltage circuit 17 is a circuit that generates a reference voltage that the external noise level detection circuit 16 uses to detect the level of the noise signal, and this reference voltage is supplied to the external noise level detection circuit 16.
The external noise level detection circuit 16 detects the level of the noise signal by comparing the reference voltage and the noise signal level. If the level of the noise signal is higher than the reference voltage (the external noise 30 may be larger than a predetermined volume). A control signal for closing the switch 14 is output. If the level of the noise signal is lower than the reference voltage (if the external noise 30 is smaller than the predetermined volume), a control signal for opening the switch 14 is output. The switch 14 is opened and closed by a control signal from the external noise level detection circuit 16 and supplies a cancel signal, which is an output signal of the noise cancel signal generation circuit 13, to the headphone amplifier 18 through the residual noise suppression LPF 15 or a residual signal. This is a switch for selecting whether to bypass the noise suppression LPF 15 and supply it to the headphone amplifier 18.
The noise canceling headphone 1 can be used in a state of being housed in a headphone housing (not shown) configured by a pair of left and right. The headphone housing may house the above-described noise canceling headphones 1 in housings on both sides or on only one side. When accommodated in the housings on both sides, the cords for inputting the musical sound signals are respectively connected to the noise canceling headphones 1 housed in the left and right housings, and for example, a mix circuit is provided in front of the headphone amplifier 18. And the cancel signal and the cancel signal and the music signal may be output from the headphone speaker 19 by the headphone amplifier 18.
In the case of headphones that are housed in one housing and the left and right headphone housings are joined with a headband, the wiring for transmitting a musical sound signal from one headphone housing to the other headphone housing It may be embedded in. The driving battery may be configured to be loaded only in one headphone housing.
According to the noise canceling headphones 1 having the above configuration, when the volume of the external noise 30 is low, a cancel signal from which the residual noise such as the microphone amplifier 12 is removed by the residual noise suppression LPF 15 is output and listened in a quiet environment. The music can be used as a high-quality noise-canceling headphone without being changed by residual noise.
When the volume of the external noise 30 is high, the switch 14 bypasses the residual noise suppression LPF 15 and outputs the cancellation signal generated by the noise cancellation signal generation circuit 13 as it is, and therefore outputs the middle and high range as it is. It is possible to cancel environmental noise in a wider frequency band.
In the embodiment described above, the residual noise suppression LPF 15 is provided in the subsequent stage of the noise cancellation signal generation circuit 13. However, the noise-canceling headphones according to the present invention are not limited to this example, and the position of the residual noise suppression LPF 15 may be after the microphone amplifier 12 or after the headphone amplifier 18. The residual noise suppression LPF 15 is used for the purpose of removing the high frequency so that the residual noise does not become annoying. When the high frequency range of the residual noise is removed, the high frequency range of the cancel signal is also removed, so that the canceling effect is reduced accordingly, but the position including the residual noise suppression LPF 15 is adjusted as described above. Thus, it is possible to obtain an optimum noise canceling headphone that can obtain a canceling effect while reducing residual noise.

次に、本発明に係るノイズキャンセルヘッドホンの第２の実施例について説明する。図２において、ノイズキャンセルヘッドホン２は、実施例１と同様に、マイクユニット１１、マイクアンプ１２、ノイズキャンセル信号生成回路１３、残留ノイズ抑制用ＬＰＦ１５、ヘッドホンアンプ１８、ヘッドホンスピーカ１９、外部ノイズレベル検出回路１６、基準電圧回路１７を備えている。実施例１と異なって、実施例１におけるスイッチ１４の代わりに、遮断周波数（以下、「ｆ０」という）制御回路２０を備えている。ここでは、ノイズキャンセルヘッドホン１と異なる構成であるｆ０制御回路２０を中心に説明する。
ｆ０制御回路２０は、外部ノイズレベル検出回路１６が、検出した騒音信号レベルに応じて出力する制御信号によって、残留ノイズ抑制用ＬＰＦ１５の遮断周波数（ｆ０）を変化させる回路である。マイクユニット１１で集音された外部ノイズ３０すなわち環境騒音のレベルが、基準電圧回路１７から供給される基準電圧よりも高ければ、残留ノイズ抑制用ＬＰＦ１５の遮断周波数を高域側に変化させて、より広い周波数帯域の周囲騒音を打ち消すことができるキャンセル信号を出力できるようにする。騒音信号のレベルが、マイクアンプ１２などの残留ノイズが目立たない程度に高いときは、遮断周波数ｆ０を高くして実質的に残留ノイズ抑制用ＬＰＦ１５の動作を無効にする。
また、騒音信号のレベルが基準電圧よりも低いときは、残留ノイズ抑制用ＬＰＦ１５の遮断周波数を低域側に変化させて、マイクアンプ１２などから生じる残留ノイズを除去して、低域のみを打ち消すキャンセル信号を出力できるようにする。すなわち、残留ノイズ抑制用ＬＰＦ１５の動作を有効にする。
上記のように構成されるノイズキャンセルヘッドホン２によれば、外部ノイズ３０の音量が小さく、騒音信号のレベルが基準電圧よりも低いときは、残留ノイズ抑制用ＬＰＦ１５の遮断周波数ｆ０を低くするようにｆ０制御回路２０を動作させる。また、外部ノイズ３０の音量が大きく、騒音信号のレベルが基準電圧よりも高いときは、残留ノイズ抑制用ＬＰＦ１５の遮断周波数ｆ０を高くするように、ｆ０制御回路２０を動作させる。このように動作させることで、外部ノイズ３０の音量が残留ノイズの音量よりも小さいときは、残留ノイズ抑制用ＬＰＦ１５の遮断周波数ｆ０を徐々に低くして、キャンセル信号に含まれる残留ノイズを低減し、外部ノイズ３０の音量が残留ノイズの音量よりも大きいときは、残留ノイズ抑制用ＬＰＦ１５の遮断周波数ｆ０を徐々に高くして、残留ノイズの低減をはかりつつ、中・高音域の雑音の低減効果を発揮するキャンセル信号を出力することができるノイズキャンセルヘッドホンを得ることができる。Next, a second embodiment of the noise cancellation headphone according to the present invention will be described. In FIG. 2, the noise canceling headphone 2 is the same as in the first embodiment. The microphone unit 11, the microphone amplifier 12, the noise canceling signal generation circuit 13, the residual noise suppression LPF 15, the headphone amplifier 18, the headphone speaker 19, and the external noise level detection A circuit 16 and a reference voltage circuit 17 are provided. Unlike the first embodiment, a cut-off frequency (hereinafter referred to as “f 0 ”) control circuit 20 is provided instead of the switch 14 in the first embodiment. Here, the f 0 control circuit 20 having a configuration different from that of the noise cancellation headphones 1 will be mainly described.
The f 0 control circuit 20 is a circuit that changes the cutoff frequency (f 0 ) of the residual noise suppression LPF 15 according to a control signal output by the external noise level detection circuit 16 according to the detected noise signal level. If the level of the external noise 30 collected by the microphone unit 11, that is, the environmental noise is higher than the reference voltage supplied from the reference voltage circuit 17, the cutoff frequency of the residual noise suppression LPF 15 is changed to the high frequency side, A cancel signal that can cancel ambient noise in a wider frequency band can be output. When the level of the noise signal is so high that the residual noise of the microphone amplifier 12 or the like is not conspicuous, the cutoff frequency f 0 is increased to substantially disable the operation of the residual noise suppressing LPF 15.
Further, when the level of the noise signal is lower than the reference voltage, the cutoff frequency of the residual noise suppression LPF 15 is changed to the low frequency side to remove the residual noise generated from the microphone amplifier 12 and the like, and only the low frequency is canceled. Enable to output a cancel signal. That is, the operation of the residual noise suppression LPF 15 is validated.
According to the noise cancellation headphones 2 configured as described above, when the volume of the external noise 30 is low and the level of the noise signal is lower than the reference voltage, the cutoff frequency f 0 of the residual noise suppression LPF 15 is lowered. operating the f 0 control circuit 20. Further, when the volume of the external noise 30 is large and the level of the noise signal is higher than the reference voltage, the f 0 control circuit 20 is operated so as to increase the cutoff frequency f 0 of the residual noise suppression LPF 15. By operating in this way, when the volume of the external noise 30 is lower than the volume of the residual noise, the cutoff frequency f 0 of the residual noise suppression LPF 15 is gradually lowered to reduce the residual noise included in the cancel signal. and, when the volume of the external noise 30 is greater than the volume of the residual noise, gradually increasing the cut-off frequency f 0 of the residual noise suppression LPF 15, while reducing the residual noise, the mid-high range noise Noise canceling headphones that can output a cancel signal that exhibits a reduction effect can be obtained.

次に、本発明に係るノイズキャンセルヘッドホンの第３の実施例について図３を用いて説明する。図３において、ノイズキャンセルヘッドホン３は、第２の実施例と同様に、マイクユニット１１、マイクアンプ１２、ノイズキャンセル信号生成回路１３、残留ノイズ抑制用ＬＰＦ１５、ヘッドホンアンプ１８、ヘッドホンスピーカ１９、外部ノイズレベル検出回路１６、基準電圧回路１７、ｆ０制御回路２０を備えて。第２の実施例と異なる点は、さらに基準電圧調整回路２１を備えている点である。そこで、ここでは基準電圧調整回路２１を中心に説明する。
基準電圧調整回路２１は、ヘッドホン筐体に設けられた図示しない操作スイッチまたはボリュームによって基準電圧回路１７に供給する基準電圧のレベルを調整可能な回路である。基準電圧調整回路２１において、利用者は基準電圧回路１７が供給する基準電圧レベルを自由に設定することができる。すなわち、この基準電圧調整回路２１の設定によって、外部ノイズレベル検出回路１６における騒音信号の検出レベルを調整し、上記のように遮断周波数ｆ０を変化させることができる。利用者は周囲の環境に応じて適宜、ノイズキャンセルヘッドホン３の特性を変化させることができるため、より使いやすいノイズキャンセルヘッドホンを得ることができる。Next, a third embodiment of the noise cancellation headphone according to the present invention will be described with reference to FIG. In FIG. 3, the noise canceling headphone 3 includes a microphone unit 11, a microphone amplifier 12, a noise canceling signal generation circuit 13, a residual noise suppressing LPF 15, a headphone amplifier 18, a headphone speaker 19, an external noise, as in the second embodiment. level detecting circuit 16, includes a reference voltage circuit 17, f 0 control circuit 20. The difference from the second embodiment is that a reference voltage adjusting circuit 21 is further provided. Therefore, here, the reference voltage adjusting circuit 21 will be mainly described.
The reference voltage adjustment circuit 21 is a circuit capable of adjusting the level of the reference voltage supplied to the reference voltage circuit 17 by an operation switch or volume (not shown) provided in the headphone housing. In the reference voltage adjustment circuit 21, the user can freely set the reference voltage level supplied by the reference voltage circuit 17. That is, by setting the reference voltage adjustment circuit 21, it is possible to adjust the detection level of the noise signal in the external noise level detection circuit 16 changes the cutoff frequency f 0 as described above. Since the user can appropriately change the characteristics of the noise canceling headphones 3 according to the surrounding environment, it is possible to obtain noise canceling headphones that are easier to use.

次に、本発明の第４の実施例について図４を用いて説明する。図４において、ノイズキャンセルヘッドホン４は、第３の実施例と同様に、マイクユニット１１、マイクアンプ１２、ノイズキャンセル信号生成回路１３、残留ノイズ抑制用ＬＰＦ１５、ヘッドホンアンプ１８、ヘッドホンスピーカ１９、外部ノイズレベル検出回路１６、基準電圧回路１７、ｆ０制御回路２０、基準電圧調整回路２１を備えている。第４の実施例が第３の実施例と異なる点は、さらに使用者が任意に調整可能なｆ０調整回路２２を備えていることである。よって、ここではｆ０調整回路２２を中心に説明する。
ｆ０調整回路２２は、残留ノイズ抑制用ＬＰＦ１５の遮断周波数ｆ０の初期値を、図示しない操作スイッチまたはボリュームによって利用者が自由に設定できるようにする回路である。ｆ０調整回路２２によって遮断周波数の初期値を設定することにより、ｆ０制御回路２０が残留ノイズ抑制用ＬＰＦ１５の遮断周波数ｆ０をプラス方向、またはマイナス方向（高い周波数、または低い周波数）に変化させる。このように、環境騒音の種類によって、利用者が任意に残留ノイズ抑制用ＬＰＦ１５の遮断周波数ｆ０を調整することができるので、利用環境により合致したキャンセル効果を発揮するノイズキャンセルヘッドホンを得ることができる。Next, a fourth embodiment of the present invention will be described with reference to FIG. In FIG. 4, the noise canceling headphone 4 includes a microphone unit 11, a microphone amplifier 12, a noise canceling signal generation circuit 13, a residual noise suppressing LPF 15, a headphone amplifier 18, a headphone speaker 19, an external noise, as in the third embodiment. level detecting circuit 16, a reference voltage circuit 17, f 0 control circuit 20, a reference voltage adjusting circuit 21. The fourth embodiment is different from the third embodiment in that an f 0 adjustment circuit 22 that can be arbitrarily adjusted by the user is provided. Therefore, here, the f 0 adjustment circuit 22 will be mainly described.
The f 0 adjustment circuit 22 is a circuit that allows the user to freely set an initial value of the cutoff frequency f 0 of the residual noise suppression LPF 15 by an operation switch or a volume (not shown). By setting the initial value of the cutoff frequency by the f 0 adjustment circuit 22, the f 0 control circuit 20 changes the cutoff frequency f 0 of the residual noise suppression LPF 15 in the positive direction or in the negative direction (high frequency or low frequency). Let Thus, the type of environmental noise, since the user can adjust the cut-off frequency f 0 of the LPF15 for any residual noise suppression, to obtain a noise-canceling headphone that exerts a canceling effect that matches the usage environment it can.

次に、本発明の第５の実施例について図５を用いて説明する。図５において、ノイズキャンセルヘッドホン５は、第４の実施例と同様に、マイクユニット１１、マイクアンプ１２、ノイズキャンセル信号生成回路１３、残留ノイズ抑制用ＬＰＦ１５、ヘッドホンアンプ１８、ヘッドホンスピーカ１９、外部ノイズレベル検出回路１６、基準電圧回路１７、ｆ０制御回路２０、基準電圧調整回路２１、ｆ０調整回路２２を備えている。第５の実施例が第４の実施例と異なる点は、さらに外部ノイズ周波数弁別回路２３を備えていることである。よって、ここでは、外部ノイズ周波数弁別回路２３を中心に説明する。
外部ノイズ周波数弁別回路２３は、環境騒音である外部ノイズ３０に含まれる特定の周波数成分を識別して出力する回路である。この外部ノイズ周波数弁別回路２３が識別して出力する信号のレベルを、外部ノイズレベル検出回路１６において検出する。外部ノイズ周波数弁別回路２３の出力よりも基準電圧回路１７が供給する基準電圧の方が高ければ、ｆ０制御回路２０によって設定される残留ノイズ抑制用ＬＰＦ１５の遮断周波数ｆ０を低くして、キャンセル信号に含まれるマイクアンプ１２などの残留ノイズを除去する。これにより、低域の騒音信号のみを打ち消すキャンセル信号を出力することができる。また、外部ノイズ周波数弁別回路２３の出力よりも基準電圧の方が低ければ、外部ノイズ３０の音量が大きいので、ｆ０制御回路２０によって設定される残留ノイズ抑制用ＬＰＦ１５の遮断周波数ｆ０を高くし、中・高域の外部ノイズを打ち消すことができるキャンセル信号を出力することができる。
外部ノイズ周波数弁別回路２３によって外部ノイズ３０の所定の周波数成分のレベルを検出することができれば、外部ノイズ周波数弁別回路２３に入力する騒音信号は、マイクアンプ１２、ノイズキャンセル信号生成回路１３、ヘッドホンアンプ１８のいずれの出力信号であってもよい。
このように、第５の実施例に係るノイズキャンセルヘッドホン５によれば、外部ノイズ３０に含まれる周波数成分に応じて、適宜残留雑音を除去する残留ノイズ抑制用ＬＰＦ１５の特性を変化させることにより、利用者の利用環境に適合した特性を発揮するノイズキャンセルヘッドホンを得ることができる。
なお、本明細書において「音楽信号」とは、一般的な音楽信号のほか、いわゆるオーディオ信号のことをいい、「楽音信号」という場合もある。Next, a fifth embodiment of the present invention will be described with reference to FIG. In FIG. 5, the noise canceling headphone 5 includes a microphone unit 11, a microphone amplifier 12, a noise canceling signal generation circuit 13, a residual noise suppressing LPF 15, a headphone amplifier 18, a headphone speaker 19, an external noise, as in the fourth embodiment. level detecting circuit 16, a reference voltage circuit 17, f 0 control circuit 20, a reference voltage adjusting circuit 21, f 0 adjusting circuit 22. The fifth embodiment differs from the fourth embodiment in that an external noise frequency discrimination circuit 23 is further provided. Therefore, here, the external noise frequency discrimination circuit 23 will be mainly described.
The external noise frequency discrimination circuit 23 is a circuit that identifies and outputs a specific frequency component included in the external noise 30 that is environmental noise. The external noise level detection circuit 16 detects the level of the signal identified and output by the external noise frequency discrimination circuit 23. The higher the reference voltage circuit 17 than the output of the external noise frequency discriminator circuit 23 is towards the reference voltage supplied, by lowering the cut-off frequency f 0 of the residual noise suppression LPF15 set by f 0 control circuit 20, canceling Residual noise such as the microphone amplifier 12 included in the signal is removed. Thereby, it is possible to output a cancel signal that cancels only the low-frequency noise signal. Further, the lower the better reference voltage than the output of the external noise frequency discriminating circuit 23, since the volume of the external noise 30 is large, increasing the cut-off frequency f 0 of the residual noise suppression LPF15 set by f 0 control circuit 20 In addition, it is possible to output a cancel signal that can cancel external noise in the middle / high range.
If the level of the predetermined frequency component of the external noise 30 can be detected by the external noise frequency discrimination circuit 23, the noise signal input to the external noise frequency discrimination circuit 23 is the microphone amplifier 12, the noise cancellation signal generation circuit 13, the headphone amplifier. Any of the 18 output signals may be used.
Thus, according to the noise cancellation headphones 5 according to the fifth embodiment, by changing the characteristics of the residual noise suppression LPF 15 that appropriately removes residual noise according to the frequency component included in the external noise 30, It is possible to obtain a noise-canceling headphone that exhibits characteristics suitable for the user's usage environment.
In this specification, the “music signal” refers to a so-called audio signal in addition to a general music signal, and may be referred to as a “musical sound signal”.

本発明は、ヘッドホンのタイプに限定されるものではなく、耳覆い型、耳載せ型、インナーイヤー型、カナル型など、あらゆるタイプのヘッドホンに適用可能である。
本発明は、コンサートホールやカーオーディーオなど、音楽信号を再生して出力する各種音響システムにおけるノイズキャンセル処理にも適用可能である。The present invention is not limited to the type of headphones, and can be applied to all types of headphones such as an ear covering type, an ear mounting type, an inner ear type, and a canal type.
The present invention is also applicable to noise cancellation processing in various acoustic systems that reproduce and output music signals, such as concert halls and car audio.

Claims (6)

環境騒音を電気信号に変換するマイクロホンと、
上記マイクロホンで変換される騒音信号を打ち消すキャンセル信号を生成するキャンセル信号生成手段と、
オーディオ信号と上記キャンセル信号により駆動されるスピーカと、
上記キャンセル信号の低域成分を濾過する残留ノイズ抑制用ローパスフィルター回路と、
上記騒音信号の検出レベルの基準となる電圧を生成する基準電圧回路と、
上記騒音信号と上記基準となる電圧とを比較して上記騒音信号のレベルを検出し、検出結果を示す制御信号を出力する判定回路と、
上記制御信号に応じて上記残留ノイズ抑制用ローパスフィルター回路の遮断周波数を可変させる遮断周波数制御回路と、
を有することを特徴とするノイズキャンセルヘッドホン。 A microphone that converts environmental noise into an electrical signal;
And cancellation signal generation means for generating an erasing to Cancel signal beat noise signal converted by the microphone,
A speaker driven by the audio signal and the cancellation signal,
A low-pass filter circuit for suppressing residual noise that filters the low-frequency component of the cancel signal;
A reference voltage circuit for generating a voltage serving as a reference for the detection level of the noise signal;
A decision circuit which compares the voltage to be the noise signal and the reference to detect the level of the noise signal, and outputs a control signal indicating the result detect,
A cutoff frequency control circuit that varies the cutoff frequency of the low-pass filter circuit for residual noise suppression according to the control signal;
A noise canceling headphone characterized by comprising: 上記遮断周波数制御回路は、上記判定回路において検出された騒音信号の信号レベルが、上記基準となる電圧よりも小さいときに出力される上記制御信号により、上記残留ノイズ抑制用ローパスフィルター回路の上記遮断周波数を低くする、
請求項１記載のノイズキャンセルヘッドホン。 The cutoff frequency control circuit, the signal level of the detected noise signal in the determination circuit, Ri by the said control signal output when less than the voltage becomes the reference, the low-pass filter for the residual noise suppression Lower the cutoff frequency ,
The noise canceling headphones according to claim 1 . 上記遮断周波数制御回路は、上記判定回路において検出された騒音信号の信号レベルが、上記基準となる電圧よりも大きいときに出力される上記制御信号により、上記残留ノイズ抑制用ローパスフィルター回路の上記遮断周波数を高くする、
請求項１または２記載のノイズキャンセルヘッドホン。 The cutoff frequency control circuit, the signal level of the detected noise signal in the determination circuit, Ri by the said control signal that will be output when greater than the voltage becomes the reference, the low-pass filter for the residual noise suppression Increase the cutoff frequency ,
The noise cancellation headphones according to claim 1 or 2 . 上記基準電圧回路の上記基準となる電圧を可変する基準電圧調整回路を有する、
請求項１乃至３のいずれかに記載のノイズキャンセルヘッドホン。 Having a group reference voltage adjusting circuit you vary the voltage as a said reference of said reference voltage circuit,
The noise cancellation headphones according to any one of claims 1 to 3 . 上記遮断周波数の基準となる周波数を設定する遮断周波数調整回路を有する、請求項１乃至４のいずれかに記載のノイズキャンセルヘッドホン。 The noise cancellation headphones according to any one of claims 1 to 4, further comprising a cutoff frequency adjusting circuit that sets a frequency that is a reference of the cutoff frequency. 騒音信号の所定の周波数を識別して出力する周波数弁別回路を有し、
上記判定回路は、上記周波数弁別回路からの出力と上記基準となる電圧との比較結果に応じて上記遮断周波数制御回路を動作させ、上記残留ノイズ抑制用ローパスフィルター回路の上記遮断周波数を可変する、
請求項１乃至５のいずれかに記載のノイズキャンセルヘッドホン。 Have a frequency discrimination circuit configured to identify a predetermined frequency of the noise signal,
The decision circuit, in accordance with the comparison result of the voltage to be output and the reference from the frequency discriminating circuit operates the cutoff frequency control circuit to vary the cutoff frequency of the low pass filter circuit for the residual noise suppression,
The noise cancellation headphones according to any one of claims 1 to 5 .
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