Abstract:
Existing ANC headsets have active noise reduction circuitry and a power supply in the headset. Alternate ANC headsets rely on ANC circuitry in the player and have non-standard connectors meaning that they cannot be used with any other players. An audio headset ( 90 ) having an encoder ( 54 ) and active noise cancellation audio processing device ( 80 ) having a decoder ( 32 ) are described. The encoder ( 54 ) enables the audio headset to be used in enhanced (ANC) mode when connected to a compatible audio processing device and in normal mode when connected to a non-compatible audio processing device since a standard audio jack plug can be used. Similarly the decoder ( 62 ) in the active noise cancellation audio processing device ( 80 ) enables the active noise cancellation audio processing device to be used in enhanced mode when connected to a compatible audio headset and in normal mode connected to a non-compatible audio headset since a standard audio socket can be used.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to audio headsets compatible with active noise cancelling audio processing devices and audio processing devices without noise cancelling. It further relates to active noise cancelling audio processing devices and active noise cancelling audio systems comprising audio headsets and audio processing devices. 
       BACKGROUND OF THE INVENTION 
       [0002]    It is known that active noise cancellation (ANC) is a feature in audio headsets. Currently for most systems with ANC functions, the active circuitry is built into the headset along with a power source. The headset has a pair of microphones located close to each ear to sample the noise that is to be cancelled; those signals are processed in the headset and an anti-noise signal is generated. The anti-noise signal and the playback signal coming from the player are then the mixed and amplified to the earpiece. 
         [0003]    The entire active headset is then connected to the audio device typically using a 3.5 mm jack. Cell phones, audio players and other headset devices generally use a 3.5 mM audio plug and socket for providing audio output to headphones or analogue interconnection with other audio devices. Headsets typically use a 3-connector system for stereo audio or mono audio and a microphone, and a 4-connector system for headsets with stereo output and a microphone input. 
         [0004]    Alternatively, the ANC circuitry can be built into the audio processing device itself. This has the advantage of allowing the headset to operate without a battery and it reduces the cost of a headset. A problem with this approach is that is requires additional mechanical connections to pass the noise signals, from the headset to the audio device. Currently unique mechanical designs are used to enable those systems to be interoperable with standard headphones. However, this results in a system where only one side of the device/headset pair is compatible with standard equipment. 
         [0005]    U.S. Pat. No. 7,270,554 uses additional mechanical connectors that are combined with a single standard stereo headphone connector. This enables a standard headset to be used with the audio device, but requires additional mechanical connectors for the ANC functions. 
         [0006]    Sony uses a similar approach in its noise cancelling Walkman™ players by adding a unique mechanical connection on its headset, the receiving socket can be configured to allow for both the ANC version and standard headsets. However the Sony headset cannot be used with other audio players. 
         [0007]    Therefore there is a need to develop a cheap audio headset that is compatible with standard connectors. 
       SUMMARY OF THE INVENTION 
       [0008]    According to a first aspect of the invention, there is provided an audio headset compatible with active noise cancelling audio processing devices and audio processing devices without active noise cancelling, the audio headset comprising: at least one microphone for measuring noise; an encoder for encoding a noise measurement signal received from the microphone via an input of the encoder, to produce an encoded noise measurement signal; and a connector for connecting the audio headset to an audio processing device, the connector having a terminal for carrying a microphone signal, wherein the audio headset is operable when connected to an active noise cancelling audio processing device: to output the encoded noise measurement signal via the terminal, and to receive a combined audio and anti-noise signal from the active noise cancelling audio processing device; and when connected to an audio processing device without active noise cancelling: to output either a null signal or an unencoded signal from the at least one microphone via the terminal; and to receive an audio signal from the audio processing device without active noise cancelling. 
         [0009]    By encoding the noise measurement signal, it is possible to have multiple microphone signals on a single connection between a headset and an audio processing device. This allows, for example, the standard microphone signal connector on a 3.5 mm connector to be used with ANC headsets having 2 or more microphones, when connected to an active noise cancelling audio processing device. 
         [0010]    In addition, by passing either a standard microphone signal or null signal and receiving an audio signal when connected to either an audio processing device without active noise cancellation or an audio processing device without a compatible decoder, the headset can be used with other audio devices. This is because the headset can maintain standard passive connections between the jack and the earpiece drivers (stereo or mono) when no microphone bias is provided, or when only a standard microphone bias is applied. In cases where a microphone is present it can also provide a standard microphone signal output. 
         [0011]    According to an embodiment of the invention, the power supply for the encoder is supplied via the terminal. The terminal carries a bias voltage for a microphone on the headset, so using this bias to power the encoder means that no separate power supply for the headset is required, and the power supply for the headset be connected using a standard audio connector. 
         [0012]    According to a further embodiment of the invention, the audio headset comprises at least one switch coupled to a further input of the encoder, wherein the audio headset is operable to output a signal comprising the state of the at least one switch and the encoded microphone signals. This allows multiple switches or buttons to be located on the headset for controlling different functions. These can then be encoded along with noise measurement signals and other microphone signals and sent to an audio processing device. It also allows higher current limits to be used for a microphone input line, as if the button or switch is directly in the microphone line, the standard call/release button function on a headset used for a mobile phone may not function. 
         [0013]    In a second aspect of the invention, there is provided an active noise cancelling audio processing device comprising a connector for connecting the audio processing device to an audio headset, the connector having a terminal for carrying a microphone signal, an active noise cancelling processor, a decoder having an input coupled to the terminal and an output coupled to the active noise cancelling processor; wherein the audio processing device is operable when connected to an audio headset adapted for active noise cancellation to receive an encoded noise measurement signal from the audio headset via the terminal, to use the decoder to decode the encoded noise measurement signal, and to use the active noise cancelling processor to generate a combined audio and anti-noise signal, and when connected to a audio headset not adapted for active noise cancelling to receive an unencoded microphone signal or null signal from the audio headset via the terminal, and to generate an audio signal not including an anti-noise signal. 
         [0014]    The decoder can be used to decode signals from, for example, multiple microphones in a headset, and so only one terminal is required for more than one microphone. This can allow a standard connector to be used when connecting the audio processing device to a compatible headset which is adapted for noise cancellation and has a corresponding encoder. 
         [0015]    Furthermore, because the audio processing device is also operable to receive unencoded microphone signals or null signals and to generate an audio signal without any noise cancellation, the audio processing device can also be used with other audio headsets. 
         [0016]    In a further aspect of the invention, there is provided an active noise cancellation system comprising the audio headset of any of claims  1  to  8  connectable to the active noise cancelling audio processing device of any of claims  9  to  12  by means of their respective connectors. 
         [0017]    The noise reduction signal encoding and decoding allows enhanced communication between the headset and the audio processing device so enabling active noise cancellation with standard connectors so that either component can be used with other equipment. Furthermore, the active noise reduction processing circuitry for the system is located in the audio processing device, reducing the cost of the headset. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Embodiments of the invention are now described by way of example with reference to the accompanying drawings in which: 
           [0019]      FIG. 1  illustrates an example of a known audio headset and an audio processing device; 
           [0020]      FIG. 2  shows an audio headset adapted for active noise cancellation and an active noise cancelling audio processing device according to a first embodiment of the invention; 
           [0021]      FIG. 3  illustrates an audio headset adapted for active noise cancellation and an active noise cancelling audio processing device according to a further embodiment of the invention; 
           [0022]      FIG. 4  shows an audio headset adapted for active noise cancellation and an active noise cancelling audio processing device according to another embodiment of the invention; 
           [0023]      FIG. 5  shows an example of a known audio headset and an active noise cancelling audio processing device according to another embodiment of the invention. 
           [0024]      FIG. 6  illustrates an example of an audio headset adapted for active noise cancellation and a known audio processing device according to a further embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]      FIG. 1  illustrates an example of a known audio processing system consisting of an audio headset  10  connected to an audio processing device  30 . A headset  10  has a microphone  12  adapted for speech, a first headphone or earpiece  14 , a second headphone or earpiece  16 , a connector  18  for connecting to an audio processing device. The connector can have a first headphone terminal  22 , a second headphone terminal  20 , a microphone terminal  24 , and a ground reference terminal  26 . The connecter can be a 3.5 mm audio jack according to the open mobile terminal platform standard. The switch is connected between microphone  12  and ground reference terminal  26 . Microphone  12  is connected to microphone terminal  24 . The first headphone  14  is connected to the first microphone terminal  22 . The second headphone  16  is connected to the second microphone terminal  20 . 
         [0026]    An audio processing device  30  such as a mobile phone, mp3 player or other audio playing device has a connecter  32  which can be a 3.5 mm socket. The connector has a first headphone terminal  36 , a second headphone terminal  34 , a microphone terminal  38 , and a ground reference terminal  40 . The ground reference terminal can be connected to a ground reference  42 . The audio processing device  30  provides audio signals to the first headphone terminal  36 , and second headphone terminal  34 . The audio processing device  30  can receive a microphone input signal on microphone terminal  38 . The audio processing device can also supply a microphone bias voltage to microphone terminal  38 . 
         [0027]    The audio processing device  30  is connected to the headset  10  by means of the connectors  18 ,  32 . 
         [0028]      FIG. 2  shows an active noise cancellation system with an audio headset  50  according to an embodiment of the invention and an active noise cancelling audio processing device  60  according to a further embodiment of the invention. 
         [0029]    Audio headset  50  can have headphone or earpiece  14 , a microphone  52  which can be adapted to detect ambient noise, an encoder  54 , a connector  18  which can have a headphone terminal  22 , a microphone terminal  24  and a ground reference terminal  26 . The connector  18  may be a 3.5 mm audio jack plug. Microphone  52  can be coupled to an input of the encoder  54 . An input or an output of the encoder  54  can be connected to microphone terminal  24 . A further input of the encoder  54  can be connected to a headphone terminal  22 . The headphone terminal  22  can be connected to the headphone  14 . The encoder  54  can provide an audio headset identifier signal to the microphone terminal. The frequency of the audio headset identifier signal can be outside the audible frequency. Audio processing device  60  can have a connector  32 , a decoder  62 , and an active noise processing circuit  64 . The connector can have a headphone terminal  36 , a microphone terminal  38  and a ground reference terminal  40 . The decoder can be connected to the headphone terminal  36  and the microphone terminal  38 . The decoder  62  can provide an audio processing device identifier signal to the headphone terminal. The audio processing device identifier signal can be a signal that is outside the audible frequency. The audio headset  50  and audio processing device  60  can be connected together by means of connectors  22  and  32 . 
         [0030]    In operation the active noise cancellation system can work as follows. On initial power up, the decoder  62  can provide an audio processing device identifier signal which can be received by the encoder  54 , and the encoder  54  provides an audio headset identifier signal which can be received by the decoder  62 . 
         [0031]    The encoder  62  can receive an audio processing device identifier signal; this can indicate a compatible audio processing device. The encoder can encode ambient noise detected by microphone  52 . The encoded ambient noise can be decoded by decoder  62  and the decoded microphone signal can be routed to the active noise processor  64 . The active noise processor can generate an anti-noise signal from the decoded microphone signal which is mixed with the desired audio signal. This combined anti-noise and audio signal can then be routed to the headphone terminal  36  in the active noise cancelling audio processing device  60  which is connected to terminal  22  in the audio headset  50 . 
         [0032]    In some embodiments, the power supply for the encoder  54  can be provided by the audio processing device by adapting the bias voltage and current provided on the microphone terminal  38 . 
         [0033]    In further embodiments, the audio processing device can be a mobile phone, a smart phone or other audio processing devices such as MP3 player, TV or Computer. 
         [0034]      FIG. 3  shows a further embodiment of an active noise cancellation system with an audio headset  70  and an active noise cancelling audio processing device  80 . Audio headset  70  can have headphone or earpiece  14 , a microphone  52  which can be adapted to detect ambient noise, a second microphone  72  which can be adapted to detect ambient noise, an encoder  54 , a switch  74 , a connector  18  which can have a first headphone terminal  22 , a second headphone terminal  20 , a microphone terminal  24  and a ground reference terminal  26 . The connector  18  may be a 3.5 mm audio jack plug. Microphone  52  can be coupled to an input of the encoder  54 . Second microphone  72  can be coupled to a further input of the encoder  54 . An input or an output of the encoder  54  can be connected to microphone terminal  24 . A further input of the encoder  54  can be connected to a headphone terminal  22 . The headphone terminal  22  can be connected to the first headphone  14 . Switch  74  can be coupled to an input of the encoder  54  and ground reference terminal  26 . The encoder  54  can provide an audio headset identifier signal to the microphone terminal. The frequency of the audio headset identifier signal can be outside the audible frequency. 
         [0035]    Audio processing device  60  can have a connector  32 , a decoder  62 , and an active noise processing circuit  64 . The connector can have a first headphone terminal  36 , a second headphone terminal  34 , a microphone terminal  38  and a ground reference terminal  40 . The decoder can be connected to the first and second headphone terminals  34 ,  36  and the microphone terminal  38 . The decoder  62  can provide an audio processing device identifier signal to the first headphone terminal  36 . The audio processing device identifier signal can be a signal that is outside the audible frequency. 
         [0036]    The audio headset  50  and audio processing device  60  can be connected together by means of connectors  22  and  32 . 
         [0037]    In operation the active noise cancellation system can work as follows. On initial power up, the decoder  62  can provide an audio processing device identifier signal which can be received by the encoder  54 , and the encoder  54  provides an audio headset identifier signal which can be received by the decoder  62 . 
         [0038]    The encoder  62  can receive an audio processing device identifier signal; this can indicate a compatible audio processing device. The encoder can encode ambient noise detected by microphones  52  and  72  and the state of the switch  74 . The encoded ambient noise can be decoded by decoder  62  and the decoded microphone signals from the microphones  52  and  72  can be routed to the active noise processor  64 . The active noise processor  80  can generate an anti-noise signal from the decoded microphone signal which is mixed with the desired audio signal. This combined anti-noise and audio signal can then be routed to the headphone terminal  36  in the active noise cancelling audio processing device  80  which is connected to terminal  22  in the audio headset  70 . The decoded state of the switch  74  can be routed to the active noise cancellation processor  64 . 
         [0039]    In some embodiments the encoding scheme used can be amplitude modulation with different carrier frequencies being used for first microphone  52 , second microphone  72 , and state of switch  74 . 
         [0040]    In other embodiments different inputs to the encoder can be sampled at different times. This can require the decoder  62  to provide a clock signal on the headphone terminal  36  which can be received at an input of the encoder  54 . The frequency of the clock can be greater than the audible frequency, i.e. a higher frequency than 20 KHz. 
         [0041]      FIG. 4  shows a further embodiment of an active noise cancellation system with an audio headset  90  and an active noise cancelling audio processing device  80 . Audio headset  90  can have headphone or earpiece  14 , a microphone  52  which can be adapted to detect ambient noise, a second microphone  72  which can be adapted to detect ambient noise, an encoder  54 , a switch  74 , a further switch  92 , a connector  18  which can have a first headphone terminal  22 , a second headphone terminal  20 , a microphone terminal  24  and a ground reference terminal  26 . The connector  18  may be a 3.5 mm audio jack plug. Microphone  52  can be coupled to an input of the encoder  54 . Second microphone  72  can be coupled to a further input of the encoder  54 . An input or an output of the encoder  54  can be connected to microphone terminal  24 . A further input of the encoder  54  can be connected to a headphone terminal  22 . The headphone terminal  22  can be connected to the first headphone  14 . Switch  74  can be coupled to an input of the encoder  54  and ground reference terminal  26 . Further switch  92  can be coupled to an input of the encoder  54  and ground reference terminal  26 . The encoder  54  can provide an audio headset identifier signal to the microphone terminal. The frequency of the audio headset identifier signal can be outside the audible frequency. 
         [0042]    Audio processing device  80  can have a connector  32 , a decoder  62 , and an active noise cancelling processing circuit  64 . The connector can have a first headphone terminal  36 , a second headphone terminal  34 , a microphone terminal  38  and a ground reference terminal  40 . The decoder can be connected to the first and second headphone terminals  34 ,  36  and the microphone terminal  38 . The decoder  62  can provide an audio processing device identifier signal to the first headphone terminal  36 . The audio processing device identifier signal can be a signal that is outside the audible frequency range. The audio headset  50  and audio processing device  60  can be connected together by means of connectors  22  and  32 . 
         [0043]    In operation the active noise cancellation system can work as follows. On initial power up, the decoder  62  can provide an audio processing device identifier signal which can be received by the encoder  54 , and the encoder  54  provides an audio headset identifier signal which can be received by the decoder  62 . The encoder  62  can receive an audio processing device identifier signal; this can indicate a compatible audio processing device. The encoder can encode ambient noise detected by microphones  52  and  72  and the states of the switch  74  and further switch  92 . The encoded ambient noise can be decoded by decoder  62  and the decoded microphone signals from the microphones  52  and  72  can be routed to the active noise processor  64 . The active noise processor  80  can generate an anti-noise signal from the decoded microphone signal which is mixed with the desired audio signal. This combined anti-noise and audio signal can then be routed to the headphone terminal  36  in the active noise cancelling audio processing device  80  which is connected to terminal  22  in the audio headset  90 . The decoded state of the switch  74  further switch  92  can be routed to the active noise cancellation processor  64 . 
         [0044]    In other embodiments, the decoded state of the switch  74  further switch  92  can be routed to other circuitry within the audio processing device. In further embodiments switch  74  can be a call-end button for a mobile phone. In other embodiments switch  92  can be used to switch encoder  54  between encode and non-encode function. 
         [0045]      FIG. 5  shows an audio system having a non-compatible audio headset  10  connected to an active noise cancellation audio processing device  80 . A headset  10  has a microphone  12  adapted for speech, a first headphone or earpiece  14 , a second headphone or earpiece  16 , a connector  18  for connecting to an audio processing device. The connector can have a first headphone terminal  22 , a second headphone terminal  20 , a microphone terminal  24 , and a ground reference terminal  26 . The connecter can be a 3.5 mm audio jack. The switch is connected between microphone  12  and ground reference terminal  26 . Microphone  12  is connected to microphone terminal  24 . The first headphone  14  is connected to the first microphone terminal  22 . The second headphone  16  is connected to the second microphone terminal  20 . 
         [0046]    Audio processing device  80  can have a connector  32 , a decoder  62 , and an active noise cancelling processor circuit  64 . The connector can have a first headphone terminal  36 , a second headphone terminal  34 , a microphone terminal  38  and a ground reference terminal  40 . The decoder can be connected to the first and second headphone terminals  34 ,  36  and the microphone terminal  38 . The decoder  62  can provide an audio processing device identifier signal to the first headphone terminal  36 . The audio processing device identifier signal can be a signal that is outside the audible frequency. 
         [0047]    The audio headset  10  and audio processing device  80  can be connected together by means of connectors  22  and  32 . In operation, on initial power up the audio processing device does not receive an audio headset initialization signal from audio headset  10 . The decoder  62  routes the unencoded microphone signals received on terminal  38  to other circuitry in the audio processing device. In other embodiments, the audio processing device can have a switch to manually switch between decode and non-decode operation of the decoder. 
         [0048]      FIG. 6  shows an audio headset adapted for active noise cancellation  90  connected to a non-compatible audio processing device  30 . Audio headset  90  can have headphone or earpiece  14 , a microphone  52  which can be adapted to detect ambient noise, a second microphone  72  which can be adapted to detect ambient noise, an encoder  54 , a switch  74 , a further switch  92 , a connector  18  which can have a first headphone terminal  22 , a second headphone terminal  20 , a microphone terminal  24  and a ground reference terminal  26 . The connector  18  may be a 3.5 mm audio jack plug. Microphone  52  can be coupled to an input of the encoder  54 . Second microphone  72  can be coupled to a further input of the encoder  54 . An input or an output of the encoder  54  can be connected to microphone terminal  24 . A further input of the encoder  54  can be connected to a headphone terminal  22 . The headphone terminal  22  can be connected to the first headphone  14 . Switch  74  can be coupled to an input of the encoder  54  and ground reference terminal  26 . Further switch  92  can be coupled to an input of the encoder  54  and ground reference terminal  26 . The encoder  54  can provide an audio headset identifier signal to the microphone terminal. The frequency of the audio headset identifier signal can be outside the audible frequency. 
         [0049]    An audio processing device  30  such as a mobile phone, mp3 player or other audio playing device has a connecter  32  which can be a 3.5 mm socket. The connector has a first headphone terminal  36 , a second headphone terminal  34 , a microphone terminal  38 , and a ground reference terminal  40 . The ground reference terminal can be connected to a ground reference  42 . The audio processing device  30  provides audio signals to the first headphone terminal  36 , and second headphone terminal  34 . The audio processing device  30  can receive a microphone input signal on microphone terminal  38 . The audio processing device can also supply a microphone bias voltage to microphone terminal  38 . The audio processing device  30  is connected to the audio headset  90  by means of the connectors  18 ,  32 . 
         [0050]    On power up the audio headset  90  may not receive an audio processing device identifier signal. The decoder  54  can route the unencoded microphone signal  12  to microphone terminal  24 . The decoder can couple the switch  74  to microphone  12 . 
         [0051]    In other embodiments a further switch on the audio headset  90  can switch the encoder between encode and non-encode function. In further embodiments, the encoder for the audio headset can be integrated into the microphone pre-amplifier circuit. In some embodiments of the audio headset, other switches or buttons coupled to the encoder can be provided for other functions; for example to switch between ANC and non-ANC mode. In other embodiments further microphones can be added to the headset to enable multi-microphone anti-noise reduction. 
         [0052]    In other embodiments, the active noise cancellation audio processing device  80  can modify the power supply to a higher voltage and/or current when the connection to audio headset  90  is detected. In further embodiments of active noise cancellation audio processing device  80 , the decoder  62  can be integrated with a headphone amplifier. 
         [0053]    There is described an audio headset  90  having an encoder  54  and active noise cancellation audio processing device  80  having a decoder  62 . The encoder  54  enables the audio headset to be used in enhanced (ANC) mode when connected to a compatible audio processing device and in normal mode when connected to a non-compatible audio processing device since a standard audio jack plug can be used. Similarly the decoder  62  in the active noise cancellation audio processing device  80  enables the active noise cancellation audio processing device to be used in enhanced mode when connected to a compatible audio headset and in normal mode connected to a non-compatible audio headset, since a standard audio socket can be used.