JP2008301376A - Noise canceling headphone - Google Patents
Noise canceling headphone Download PDFInfo
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- JP2008301376A JP2008301376A JP2007147455A JP2007147455A JP2008301376A JP 2008301376 A JP2008301376 A JP 2008301376A JP 2007147455 A JP2007147455 A JP 2007147455A JP 2007147455 A JP2007147455 A JP 2007147455A JP 2008301376 A JP2008301376 A JP 2008301376A
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- 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
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- 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
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- 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
- G10K11/1783—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 handling or detecting of non-standard events or conditions, e.g. changing operating modes under specific operating conditions
- G10K11/17833—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 handling or detecting of non-standard events or conditions, e.g. changing operating modes under specific operating conditions by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels
- G10K11/17835—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 handling or detecting of non-standard events or conditions, e.g. changing operating modes under specific operating conditions by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels using detection of abnormal input signals
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- 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
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- 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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- 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
- G10K2210/50—Miscellaneous
- G10K2210/503—Diagnostics; Stability; Alarms; Failsafe
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Multimedia (AREA)
- Headphones And Earphones (AREA)
- Soundproofing, Sound Blocking, And Sound Damping (AREA)
- Circuit For Audible Band Transducer (AREA)
Abstract
Description
本発明は、ノイズのキャンセル音を生成し楽音と合成することでノイズキャンセル処理を行なうノイズキャンセルヘッドホンに関するものであって、特に、ノイズの入力レベルが過大であっても最適なキャンセル処理を行なう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 relates to a noise canceling headphone that performs noise canceling processing by generating a noise canceling sound and synthesizing it with a musical sound. In particular, the present invention performs optimal canceling processing even when the noise input level is excessive. The present invention relates to a noise canceling headphone capable of
様々な形態の携帯型音楽プレーヤの普及に伴い、それに使用するヘッドホンもより高性能のものが求められ、さらに、街頭や乗り物の中で音楽を聴こうとする場合に、周囲の騒音に邪魔されることなく、音楽のみが聞こえるようにしたノイズキャンセルヘッドホンも望まれるようになってきた。音楽の再生音に混じって周囲の騒音が耳に入ると、ヘッドホンで再生される音楽が高音質のものであっても、騒音によってかき消されてしまい、高音質の音楽を楽しむことができなくなるからである。また、騒音の中で音楽を聴こうとすると、音量を上げて聞きがちになり、音量を上げることによってヘッドホンから外に向かって音漏れが生じ、乗り物などの中では周囲の人たちにとって不愉快な騒音源になるという問題もある。このような背景があって、ノイズキャンセルヘッドホンが普及し始めている。 With the widespread use of portable music players in various forms, headphones with higher performance are required, and when listening to music on the street or in a vehicle, it is disturbed by ambient noise. In addition, there has been a demand for noise canceling headphones that allow only music to be heard. If ambient noise is mixed with music playback sound, even if the music played on the headphones is of high quality, it will be erased by the noise and you will not be able to enjoy high quality music. It is. In addition, when listening to music in the noise, it tends to be heard by increasing the volume, and by increasing the volume, sound leaks out from the headphones, which is unpleasant for the surrounding people in vehicles etc. There is also a problem of becoming a noise source. With this background, noise-canceling headphones are beginning to spread.
最近では、アナログ方式やデジタル方式のノイズキャンセルヘッドホンが提案されている。そのうち、デジタル方式の構造例を図３に示す。図３において、符号１０はキャンセル信号を生成するＤＳＰ（デジタル信号プロセッサ）を中心として構成されるキャンセル信号生成手段（以下「ＣＰ」とする）である。図３は左右一対で構成されるノイズキャンセルヘッドホン筐体の片側のみを示した概略図である。ヘッドホンユニット１には、当該ノイズキャンセルヘッドホンの利用者の周囲のノイズＮを集音するためのヘッドホンユニット１の外側に向けて設置されたマイク１００と、ヘットホンユニット１の一部に設けた貫通孔１０２と、マイク１００が集音したノイズＮに対するキャンセル信号を生成し、音源から入力された再生信号Ｓを混合するＣＰ１０と、ＣＰ１０の出力を利用者の耳２００に向けて出力するスピーカ１０１が備わっている。また、ヘッドホンユニット１にはＣＰ１０の駆動電源である図示しない電池が収まっている。 Recently, analog and digital noise cancellation headphones have been proposed. Among them, an example of a digital structure is shown in FIG. In FIG. 3, reference numeral 10 denotes a cancel signal generating means (hereinafter referred to as “CP”) configured around a DSP (digital signal processor) that generates a cancel signal. FIG. 3 is a schematic view showing only one side of a noise-canceling headphone housing composed of a pair of left and right. The headphone unit 1 includes a microphone 100 installed toward the outside of the headphone unit 1 for collecting noise N around the user of the noise canceling headphone, and a through hole provided in a part of the headphone unit 1. 102, CP10 that generates a cancel signal for noise N collected by microphone 100, mixes reproduction signal S input from the sound source, and speaker 101 that outputs the output of CP10 toward user's ear 200 are provided. ing. Further, the headphone unit 1 contains a battery (not shown) which is a driving power source for the CP 10.
図３に示すように、マイク１００をヘッドホンユニットの外側に向けて設置するタイプは、ＣＰ１０内部に具備するＤＳＰにおいて、予め決められたフィルター係数によってキャンセル量を算出して、キャンセル信号を生成する方法が用いられる。デジタルノイズキャンセルヘッドホンには上記のタイプの他に、マイク１００をヘッドホンユニットの内側に向けて設置するタイプがある。このタイプの場合は、ヘッドホンユニット１を透過したノイズＮと音源からの再生信号Ｓをマイク１００が集音し、ＣＰ１０が具備するＤＳＰにおいて、この集音した信号から再生信号Ｓを差し引いた信号によってノイズキャンセル信号を生成する。 As shown in FIG. 3, the type in which the microphone 100 is installed toward the outside of the headphone unit is a method of generating a cancellation signal by calculating a cancellation amount using a predetermined filter coefficient in a DSP provided in the CP 10. Is used. In addition to the above-mentioned types of digital noise canceling headphones, there is a type in which the microphone 100 is installed facing the headphone unit. In the case of this type, the microphone 100 collects the noise N transmitted through the headphone unit 1 and the reproduction signal S from the sound source, and a signal obtained by subtracting the reproduction signal S from the collected signal in the DSP of the CP 10. Generate a noise cancellation signal.
図４はＣＰ１０の機能ブロック図である。図４において、ＣＰ１０は、マイク１００が集音したノイズＮをデジタル信号に変換するＡ／Ｄコンバータ１１と、Ａ／Ｄコンバータ１１と、デジタル信号に変換されたノイズＮとキャンセル信号を生成するために必要となるフィルター係数によりキャンセル信号を生成する積和演算器を具備するＤＳＰ１２と、キャンセル信号をアナログ信号に変換するＤ／Ａコンバータ１３と、アナログ信号に変換されたキャンセル信号と音源Ｓから入力されるオーディオ信号を混合してスピーカ１０１に出力するミキサ１４とを有してなる。 FIG. 4 is a functional block diagram of CP10. In FIG. 4, the CP 10 generates an A / D converter 11 that converts noise N collected by the microphone 100 into a digital signal, an A / D converter 11, noise N converted into a digital signal, and a cancel signal. DSP 12 having a product-sum operation unit for generating a cancel signal with a filter coefficient necessary for the input, a D / A converter 13 for converting the cancel signal into an analog signal, a cancel signal converted into an analog signal and input from sound source S And a mixer 14 that mixes the audio signals to be output to the speaker 101.
上記従来型のヘッドホンユニット１において、マイク１００が、大音量のノイズＮを捉えると、マイク１００から過大な電圧レベルのノイズＮがＣＰ１０に入力されることになる。このような過大な電圧レベルのノイズＮがＣＰ１０に入力されると、ノイズＮをデジタル信号に変換するためのＡ／Ｄコンバータ１１がオーバーフローを起こし、入力されたノイズＮに対して正常なデジタル信号を生成することができなくなる。 In the conventional headphone unit 1, if the microphone 100 captures a loud noise N, an excessive voltage level noise N is input from the microphone 100 to the CP 10. When such an excessive voltage level noise N is input to the CP 10, the A / D converter 11 for converting the noise N into a digital signal causes an overflow, and a normal digital signal with respect to the input noise N is generated. Can no longer be generated.
キャンセル信号は、Ａ／Ｄコンバータ１１が生成するデジタル信号に基づいて生成されるので、Ａ／Ｄコンバータ１１がオーバーフローを起すと、入力されたノイズＮに対して有効なキャンセル信号を生成することができなくなる。また、Ａ／Ｄコンバータ１１自体がオーバーフローによるノイズを発生し、ノイズＮの他にＣＰ１０において別のノイズを発生させることになる。 Since the cancel signal is generated based on the digital signal generated by the A / D converter 11, when the A / D converter 11 overflows, an effective cancel signal can be generated for the input noise N. become unable. Further, the A / D converter 11 itself generates noise due to overflow, and in addition to the noise N, another noise is generated in the CP 10.
このような過大な入力に対して回路を正常に動作させるための種々の発明がなされている。入力電圧が過大であると内部回路を破損する恐れがあることから、過大入力保護回路を設けて、入力値に応じて当該保護回路を動作させる発明が知られている（例えば特許文献１参照）。また、デジタルノイズキャンセルヘッドホンにおいて、集音する周囲雑音のレベルが高いと信号レベルに飽和が生じるため生成されるノイズキャンセル信号に歪みが生じ、また、入力信号が過小であると、ノイズを除去する処理性能の低下につながるため、ノイズを集音するマイクロホンの出力信号レベルが一定となるように、信号レベル調整手段を有す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２参照）。 Various inventions have been made for operating a circuit normally for such an excessive input. Since an internal circuit may be damaged when an input voltage is excessive, an invention is known in which an excessive input protection circuit is provided and the protection circuit is operated according to an input value (see, for example, Patent Document 1). . In addition, in digital noise cancellation headphones, if the level of ambient noise to be collected is high, the signal level is saturated, resulting in distortion in the generated noise cancellation signal, and if the input signal is too low, noise is removed. A noise canceling headphone having a signal level adjusting means is known so that the output signal level of a microphone that collects noise is constant because it leads to a decrease in processing performance (see, for example, Patent Document 2).
しかし上記の文献に記載されている技術を用いて過大な入力信号（ノイズＮ）を調整し、キャンセル信号の生成処理を正常に行なうようにした場合、別の課題が生じる。すなわち、キャンセル信号は調整された入力信号を元にして生成されるのであるから、本来のノイズＮのレベルには対応していないキャンセル信号となる。つまり、ノイズＮをキャンセルする効果が低いキャンセル信号が生成されることになる。 However, when the excessive input signal (noise N) is adjusted using the technique described in the above-mentioned document and the cancel signal generation process is normally performed, another problem arises. That is, since the cancel signal is generated based on the adjusted input signal, the cancel signal does not correspond to the original noise N level. That is, a cancel signal having a low effect of canceling the noise N is generated.
本発明は、上記課題を鑑みてなされたもので、ノイズＮが過大である場合には、Ａ／Ｄコンバータがオーバーフローを起さない程度に信号レベルを減衰させ、生成されたノイズキャンセル信号に対して、前段の減衰処理に対応した増幅処理を行なうことで、過大なノイズＮに対しても効果的なキャンセル信号を生成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。 The present invention has been made in view of the above problems. When the noise N is excessive, the signal level is attenuated to such an extent that the A / D converter does not overflow, and the generated noise cancellation signal is reduced. Thus, an object of the present invention is to provide a noise canceling headphone that can generate an effective cancel signal even for excessive noise N by performing an amplification process corresponding to the preceding attenuation process.
本発明は、周囲の騒音を電気信号に変換するマイクロホンと、マイクロホンで変換される騒音信号の位相を反転させて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を混合して信号・音響変換素子に入力する混合器と、を備えるノイズキャンセルヘッドホンにおいて、上記キャンセル信号生成手段は、上記騒音信号が過大入力であるか否かを判定する判定手段，上記判定手段が過大入力であると判定した騒音信号を減衰させる減衰器，上記判定手段が過大入力であると判定し減衰された騒音信号によって生成されたキャンセル信号を増幅する増幅器を有することを最も主要な特徴とする。 The present invention includes a microphone that converts ambient noise into an electrical signal, cancel signal generation means that generates a cancel signal by inverting the phase of the noise signal converted by the microphone, an audio signal and the cancel signal mixed together. A noise canceling headphone including a mixer for inputting to a signal / acoustic transducer, wherein the cancel signal generating means includes a determining means for determining whether the noise signal is an excessive input, and the determining means is an excessive input. The main features include an attenuator for attenuating a noise signal determined to be present, and an amplifier for amplifying a cancel signal generated by the attenuated noise signal determined by the determination means being an excessive input.
本発明によれば、ノイズキャンセルヘッドホンにおいて、集音した周囲ノイズが過大である場合、入力するノイズレベルを減衰器によって減衰させ、それに基づいて生成したキャンセル信号を増幅することで、正常なキャンセル信号を生成することができるので、効果的なノイズキャンセル処理を行なうことができるようになる。過大入力に起因してＡ／Ｄコンバータで発生するノイズを防止することができる。 According to the present invention, in the noise canceling headphones, when the collected ambient noise is excessive, the normal cancel signal is obtained by attenuating the input noise level by the attenuator and amplifying the cancel signal generated based on the attenuated noise level. Therefore, effective noise cancellation processing can be performed. Noise generated in the A / D converter due to excessive input can be prevented.
本発明に係るノイズキャンセルヘッドホンについて図を用いて説明する。本発明の特徴は図３に示したノイズキャンセルヘッドホンが具備するキャンセル信号生成手段（ＣＰ）の内部構成にある。従って以下において、本発明に係るノイズキャンセルヘッドホンが具備するキャンセル信号生成手段（ＣＰ）について説明をする。図１は、本発明にかかるキャンセル信号生成手段の構成の例を示す機能ブロック図である。背景技術において用いた図４におけるＣＰ１０の内部構成部分と同一の構成部分には同一の符号を付し、その部分の説明は省略する。 The noise cancellation headphones according to the present invention will be described with reference to the drawings. The feature of the present invention resides in the internal configuration of the cancel signal generating means (CP) provided in the noise canceling headphones shown in FIG. Therefore, in the following, the cancel signal generating means (CP) provided in the noise canceling headphones according to the present invention will be described. FIG. 1 is a functional block diagram showing an example of the configuration of the cancel signal generating means according to the present invention. The same reference numerals are given to the same components as the internal components of the CP 10 in FIG. 4 used in the background art, and the description of those components is omitted.
図１において、キャンセル信号生成手段（ＣＰ）２０は、前述のＣＰ１０を構成する各手段に加えて、マイク１００から入力されるノイズＮの信号レベルを検出し、ＣＰ２０への入力として過大な電圧レベルであるか否かを判定する信号検出器１５と、信号検出器１５によって過大な電圧レベルであると判定された場合、当該ノイズＮを減衰させる減衰器１６と、信号検出器１５によって過大電圧レベルであると判定され減衰器１６によって減衰された当該ノイズＮによって生成されたキャンセル信号を増幅させる増幅器１７を有している。減衰器１６は、マイク１００とＡ／Ｄコンバータ１１の間におかれていて、マイク１００から入力されるノイズＮのアナログ信号を減衰させることができるように構成されている。増幅器１７は、Ｄ／Ａコンバータ１３によってアナログ信号に変換されたキャンセル信号を増幅してミキサ１４に入力するように構成されている。 In FIG. 1, the cancel signal generation means (CP) 20 detects the signal level of the noise N input from the microphone 100 in addition to each means constituting the CP 10 described above, and an excessive voltage level as an input to the CP 20. If the signal detector 15 determines whether or not the voltage level is an excessive voltage level, the signal detector 15 attenuates the noise N and the signal detector 15 causes the excessive voltage level. And an amplifier 17 that amplifies the cancel signal generated by the noise N that has been determined to be attenuated by the attenuator 16. The attenuator 16 is disposed between the microphone 100 and the A / D converter 11 and configured to attenuate an analog signal of noise N input from the microphone 100. The amplifier 17 is configured to amplify the cancel signal converted into an analog signal by the D / A converter 13 and input the amplified signal to the mixer 14.
信号検出器１５は、ノイズＮの電圧レベルを検出して予め規定している閾値を超えるか否かを判定し、その判定結果によって減衰器１６と増幅器１７の動作を制御する手段である。ノイズＮが閾値を超えている場合には、当該ノイズＮを減衰するように減衰器１６を動作させ、併せて、減衰させたノイズＮに基づくキャンセル信号を増幅するように増幅器１７を動作させる。減衰器１６の減衰率と増幅器１７の増幅率が可変である場合には、上記の動作指示と併せてノイズＮの電圧レベルを、減衰器１６及び増幅器１７に通知する。 The signal detector 15 is means for detecting the voltage level of the noise N and determining whether or not a predetermined threshold value is exceeded, and controlling the operations of the attenuator 16 and the amplifier 17 based on the determination result. When the noise N exceeds the threshold value, the attenuator 16 is operated so as to attenuate the noise N, and at the same time, the amplifier 17 is operated so as to amplify the cancel signal based on the attenuated noise N. When the attenuation factor of the attenuator 16 and the amplification factor of the amplifier 17 are variable, the voltage level of the noise N is notified to the attenuator 16 and the amplifier 17 together with the operation instruction.
減衰器１６は、信号検出器１５の指示によって動作して、ノイズＮの電圧レベルを減衰させる。減衰率は固定であっても、可変値であってもよい。減衰率が可変値である場合、信号検出器１５の指示と同時に通知されるノイズＮの電圧レベルに応じて減衰率を決定する。 The attenuator 16 operates according to an instruction from the signal detector 15 to attenuate the voltage level of the noise N. The attenuation rate may be fixed or variable. When the attenuation rate is a variable value, the attenuation rate is determined according to the voltage level of the noise N notified at the same time as the instruction of the signal detector 15.
増幅器１７は、信号検出器１５の指示によって動作して、減衰させたノイズＮによって生成したキャンセル信号の電圧レベルを増幅する。増幅率は、固定値であっても、可変値であってもよい。増幅率が可変である場合、信号検出器１５の指示と同時に通知されるノイズＮの電圧レベルに応じて増幅率を決定する。 The amplifier 17 operates according to an instruction from the signal detector 15 and amplifies the voltage level of the cancel signal generated by the attenuated noise N. The amplification factor may be a fixed value or a variable value. When the amplification factor is variable, the amplification factor is determined according to the voltage level of the noise N that is notified simultaneously with the instruction of the signal detector 15.
次に本発明にかかるノイズキャンセルヘッドホンが用いるキャンセル信号生成方法について、図２のフローチャートを用いて説明する。図２において、各処理のステップは（２０１）、（２０２）、・・・のように表示して説明する。また、当該実施例における減衰率と増幅率は固定値であるものとする。まず、ある時間ｔにおいてマイク１００から入力されたノイズＮ（以下「ｘ（ｔ）」とする）が、Ａ／Ｄコンバータ１１の入力として過大であるか否かを信号検出器１５が判定する（２０１）。ｘ（ｔ）がＡ／Ｄコンバータ１１の入力として過大なレベルではなければ（２０１のＹ）、このｘ（ｔ）は、減衰器１６を通過してＡ／Ｄコンバータ１１においてデジタル信号に変換され、このデジタル信号に基づいてＤＳＰ１２によってキャンセル信号を生成する。生成されたキャンセル信号はＤ／Ａコンバータ１３によってアナログ信号に変換され、増幅器１７を通過してミキサ１４に入力される（２０２）。ミキサ１４は音源からの再生信号Ｓと上記キャンセル信号を混合しスピーカ１０１に出力する。 Next, a cancellation signal generation method used by the noise cancellation headphones according to the present invention will be described with reference to the flowchart of FIG. In FIG. 2, the steps of each process are displayed and described as (201), (202),. Further, it is assumed that the attenuation factor and the amplification factor in the embodiment are fixed values. First, the signal detector 15 determines whether or not the noise N (hereinafter referred to as “x (t)”) input from the microphone 100 at a certain time t is excessive as the input of the A / D converter 11 ( 201). If x (t) is not an excessive level as an input to the A / D converter 11 (Y in 201), this x (t) passes through the attenuator 16 and is converted into a digital signal in the A / D converter 11. A cancel signal is generated by the DSP 12 based on the digital signal. The generated cancel signal is converted into an analog signal by the D / A converter 13, passes through the amplifier 17, and is input to the mixer 14 (202). The mixer 14 mixes the reproduction signal S from the sound source and the cancel signal and outputs the mixed signal to the speaker 101.
ｘ（ｔ）がＡ／Ｄコンバータ１１の入力として過大なレベルであると、信号検出器１５が判定した場合（２０１のＮ）、減衰器１６を動作させてｘ（ｔ）を規定された減衰率によって減衰させてＡ／Ｄコンバータ１１に入力する（２０３）。Ａ／Ｄコンバータ１１は、減衰したｘ（ｔ）をデジタル信号に変換し、このデジタル信号に基づいてＤＳＰ１２がキャンセル信号を生成する。生成されたキャンセル信号はＤ／Ａコンバータ１３によってアナログ信号に変換されて増幅器１７に入力される。増幅器１７は、信号検出器１５の指示によって上記入力されたキャンセル信号を規定された増幅率によって増幅した後にミキサ１４に入力する（２０５）。ミキサ１４は音源Ｓと上記キャンセル信号を混合しスピーカ１０１に出力する。 When the signal detector 15 determines that x (t) is an excessive level as an input to the A / D converter 11 (N in 201), the attenuator 16 is operated to set the attenuation specified by x (t). The signal is attenuated by the rate and input to the A / D converter 11 (203). The A / D converter 11 converts the attenuated x (t) into a digital signal, and the DSP 12 generates a cancel signal based on the digital signal. The generated cancel signal is converted into an analog signal by the D / A converter 13 and input to the amplifier 17. The amplifier 17 amplifies the input cancel signal by a prescribed amplification factor according to an instruction from the signal detector 15 and then inputs it to the mixer 14 (205). The mixer 14 mixes the sound source S and the cancel signal and outputs them to the speaker 101.
次に、減衰率及び増幅率が可変である場合の実施例を説明する。先ず、マイク１００から入力されたノイズＮにおけるｘ（ｔ）が、Ａ／Ｄコンバータ１１の入力として過大であると信号検出器１５において判定された場合、信号検出器１５は、減衰器１６及び増幅器１７への動作指示とともに、ｘ（ｔ）の電圧レベルを通知する（２０１のＮ）。 Next, an embodiment in which the attenuation factor and the amplification factor are variable will be described. First, when the signal detector 15 determines that x (t) in the noise N input from the microphone 100 is excessive as the input of the A / D converter 11, the signal detector 15 includes the attenuator 16 and the amplifier. Along with the operation instruction to 17, the voltage level of x (t) is notified (N in 201).
減衰器１６は、信号検出器１５の動作指示と共に通知されたｘ（ｔ）の電圧に応じて減衰率を決定してｘ（ｔ）を減衰させ、Ａ／Ｄコンバータ１１に入力する（２０３）。Ａ／Ｄコンバータ１１は入力されたｘ（ｔ）をデジタル信号に変換し、このデジタル信号に基づいてＤＳＰ１２においてキャンセル信号を生成し、Ｄ／Ａコンバータ１３によってこのキャンセル信号はアナログ信号に変換されて増幅器１７に入力される（２０４）。増幅器１７は、信号検出器１５の動作指示と共に通知されたｘ（ｔ）の電圧に応じて増幅率を決定して上記キャンセル信号を増幅し、ミキサ１４に入力する（２０５）。ミキサ１４は音源Ｓと上記キャンセル信号を混合しスピーカ１０１に出力する。 The attenuator 16 determines an attenuation rate according to the voltage of x (t) notified together with the operation instruction of the signal detector 15, attenuates x (t), and inputs it to the A / D converter 11 (203). . The A / D converter 11 converts the input x (t) into a digital signal, a DSP 12 generates a cancel signal based on this digital signal, and the cancel signal is converted into an analog signal by the D / A converter 13. It is input to the amplifier 17 (204). The amplifier 17 determines the amplification factor according to the voltage of x (t) notified together with the operation instruction of the signal detector 15, amplifies the cancel signal, and inputs it to the mixer 14 (205). The mixer 14 mixes the sound source S and the cancel signal and outputs them to the speaker 101.
上記のように、マイク１００が捉えたノイズＮがＡ／Ｄコンバータ１１にとって過大な入力レベルであれば、所定の減衰処理をして、正常にキャンセル信号を生成した後に、キャンセル信号を上記減衰処理の減衰率に応じた増幅率で増幅処理をすることができるので、効果的なノイズキャンセルをすることができる。また、過大なノイズＮをマイク１００が捉えた場合であっても、Ａ／Ｄコンバータのオーバーフローによるノイズを防止することができる。 As described above, if the noise N captured by the microphone 100 is an excessive input level for the A / D converter 11, a predetermined attenuation process is performed and a cancel signal is normally generated. Since the amplification process can be performed at an amplification factor corresponding to the attenuation factor, effective noise cancellation can be performed. Even when the microphone 100 captures excessive noise N, noise due to overflow of the A / D converter can be prevented.
２０ ＣＰ
１５ 信号検出器
１６ 減衰器
１７ 増幅器
20 CP
15 Signal detector 16 Attenuator 17 Amplifier
Claims (5)
上記キャンセル信号生成手段は、
上記騒音信号が過大入力であるか否かを判定する判定手段、
上記判定手段が過大入力であると判定した騒音信号を減衰させる減衰器、
上記判定手段が過大入力であると判定し、減衰された騒音信号によって生成されたキャンセル信号を増幅する増幅器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 ambient noise into an electrical signal, cancellation signal generation means that generates a cancellation signal by inverting the phase of the noise signal converted by the microphone, and signal / acoustic conversion by mixing the audio signal and the cancellation signal A noise canceling headphone comprising a mixer for inputting to the element,
The cancel signal generating means includes
Determining means for determining whether or not the noise signal is an excessive input;
An attenuator for attenuating the noise signal determined by the determination means to be an excessive input;
A noise-canceling headphone comprising: an amplifier that amplifies a cancel signal generated by the attenuated noise signal when the determination unit determines that the input is excessive.
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| JP2010157787A (en) * | 2008-12-26 | 2010-07-15 | Victor Co Of Japan Ltd | Headphone |
| WO2010126947A1 (en) * | 2009-04-29 | 2010-11-04 | Bose Corporation | Feedforward-based anr adjustment responsive to environmental noise levels |
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| JP2004320167A (en) * | 2003-04-11 | 2004-11-11 | Matsushita Electric Ind Co Ltd | Communication system, audio processing apparatus, audio control apparatus and communication terminal apparatus |
| WO2007046435A1 (en) * | 2005-10-21 | 2007-04-26 | Matsushita Electric Industrial Co., Ltd. | Noise control device |
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| JPH09331377A (en) * | 1996-06-12 | 1997-12-22 | Nec Corp | Noise cancellation circuit |
| JPH1066185A (en) * | 1996-08-21 | 1998-03-06 | Sony Corp | Automatic volume-controlling device |
| JP2004320167A (en) * | 2003-04-11 | 2004-11-11 | Matsushita Electric Ind Co Ltd | Communication system, audio processing apparatus, audio control apparatus and communication terminal apparatus |
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| JP2010157787A (en) * | 2008-12-26 | 2010-07-15 | Victor Co Of Japan Ltd | Headphone |
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