Abstract:
A talk-through system for hearing protectors such as headphones, helmets, earplugs and the like, in which separate left and right microphones are controlled by separate left and right switches. The microphones allow ambient sound to be heard by the wearer of the hearing protector, and normally the wearer hears audio from both microphones in the appropriate ears. Pushing a switch causes the audio from the ear on which the switch is mounted to be enhanced and, preferably, switched to both ears. Various arrangements of control logic are provided such that activation of a switch can cause changes in audio processing.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims one or more inventions which were disclosed in Provisional Application No. 61/182,921, filed Jun. 1, 2009, entitled “Talk-Through Listening Device Channel Switching”. The benefit under 35 USC §119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference. 
     
    
     ACKNOWLEDGMENT OF GOVERNMENT SUPPORT 
       [0002]    This invention was made with Government support under SBIR Phase II contract N68335-06-C-0372, awarded by the US Navy. The government has certain rights in the invention. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The invention pertains to the field of hearing protection. More particularly, the invention pertains to hearing protectors having talk-through capability. 
         [0005]    2. Description of Related Art 
         [0006]    Talk-through listening systems typically comprise hearing protection devices (i.e. earplugs, headsets, helmets) with microphones mounted on their outside surface. The microphones convert sound pressure levels (SPLs) to an electrical signal. The electrical signals are amplified and used to drive audio transducers such as speakers in headphones, helmets, or earplugs or the like. Electronic automatic gain control and limiting devices ensure that the SPL generated in the canals of the user are kept within safe levels. In this way, the user can monitor sound in a high-SPL environment at safe SPLs. 
         [0007]    One example of such an environment is the flight deck of aircraft carriers. Aircraft maintainers need to service aircraft under extremely high noise conditions. However, they need to be aware of their surroundings and must communicate to each other. The maintainers must know if a vehicle or plane is approaching from areas outside of their view. For this, they use acoustic cues. Moreover, the maintainers often need to communicate with each other face-to-face in high acoustic noise, without the use of radios. 
       SUMMARY OF THE INVENTION 
       [0008]    The invention presents a talk-through system for hearing protectors such as headphones, helmets, earplugs and the like, in which separate left and right microphones are controlled by separate left and right switches. The microphones allow ambient sound to be heard by the wearer of the hearing protector, and normally the wearer hears audio from both microphones in the appropriate ears. Pushing a switch causes the audio from the ear on which the switch is mounted to be enhanced and, preferably, switched to both ears. Various arrangements of control logic are provided such that activation of a switch can cause changes in audio processing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0009]      FIG. 1  shows a diagram of a talk-through headphone system 
           [0010]      FIG. 2  shows a block diagram of one embodiment of the invention 
           [0011]      FIG. 3  shows a block diagram of an alternative embodiment of the invention 
           [0012]      FIG. 4  shows a block diagram of another alternative embodiment of the invention 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    The system of the invention can provide a means to improve face-to-face speech communications of individuals using talk-through systems. 
         [0014]    A drawing of a talk-through headset system useful with the system of the invention is shown in diagrammatic form in  FIG. 1 . A hearing protection device, shown as headset  13 , has a right ear protector (earcup  1 ) and a left protector (earcup  2 ) to reduce the amount of outside noise entering the ears of the user  14 . The earcups  1  and  2  have microphones  3  and  4 , respectively, which are directed to pick up sounds outside of the earcups. Each microphone signal is amplified and processed by a processor circuit  5  and  6  and this signal is input to speakers  7  and  8 , one in each of earcups  1  and  2 . 
         [0015]    The microphone signal can be fed to the user via a speaker located within the earcup, as shown in  FIG. 1 , or within an earplug under the earcup. In this way, natural hearing is restored to the user. Electronic circuits can be used to automatically adjust the gain of the ambient noise signal which turn down the volume automatically in high noise environments and/or compress the signal to prevent hearing damage. A volume control can be provided to vary the volume of the ambient signal to comfortable levels. 
         [0016]    The switching system can be used on helmets, headsets, and in-ear communications devices as well as other devices. 
         [0017]    Switches  9  and  10  are used to control the switching and speech-enhancing circuitry, enabling the user to hear acoustic speech communications more clearly. Switches  9  and  10  are preferably pushbuttons, but it will be understood that other kinds of switches could be substituted within the teachings of the invention. 
         [0018]    It is advantageous to have the switches  9  and  10  located generally behind the earcups  1  and  2 . When the user  14  uses his/her thumb to press the switch  9  or  10 , he/she forms a “cup shape” around the microphone. This “cupping” is often used by persons in everyday life not using any headgear when they wish to hear speech better. The cupping shields sounds from the rear and amplifies sounds from the front. In addition, the cupping amplifies sounds in the speech frequency band. 
         [0019]    Locating the switches in this way results in improved speech intelligibility when the speech is hard to hear and/or there is significant background noise and also results in an intuitive procedure. Alternatively, the switches  9  and  10  can be mounted elsewhere on the hearing protector, or on helmets, earplug earshells, cables, or on a separate control box or other position as may be desired. 
         [0020]    Referring to the embodiment shown in  FIG. 2 , switch  9  on the right side  1  has two ganged sets of contacts—contacts  9   no  are normally open, and contacts  9   nc  are normally closed. Similarly, switch  10  on the left side  2  has normally open contacts  10   no  and normally closed contacts  10   nc.    
         [0021]    Audio signals from right-side microphone  3  pass through normally-closed contacts  10   nc  of left hand switch  10  into one input of summing amplifier  21 . The output of the summing amplifier  21  is further amplified and, optionally filtered or otherwise processed in processor  5 , and the amplified signal is fed to right speaker  7 . The left side  3  operates similarly—audio signals from left-side microphone  4  pass through normally-closed contacts  9   nc  of right hand switch  9  into one input of summing amplifier  22 . The output of the summing amplifier  22  is further amplified and, optionally filtered or otherwise processed in processor  6 , and the amplified signal is fed to left speaker  8 . The audio signals from right-side microphone  3  are also connected to the normally open contacts  9   no  of right hand switch  9 , and the audio signals from left-side microphone  4  are also connected to normally open contacts  10   no  of left hand switch  10 . 
         [0022]    Thus, under normal operation, the earcups  1  and  2  block most of the ambient acoustic noise from the surroundings. With neither left switch  10  nor right switch  9  pressed, the microphones  3  and  4  pick up ambient sounds which, routed through the normally closed contacts  10   nc  and  9   nc  to summing amplifiers  21  and  22  and processors  5  and  6 , are heard by the user  14  in speakers  7  and  8 , respectively. 
         [0023]    During face-to-face communications the user  14  may opt to push the left switch  10  or right switch  9 , depending on which side the person talking to them is standing, or on which side a sound the user wants to hear is coming from. When the user pushes left hand switch  10 , the normally open contacts  10   no  are closed routing the signal from left microphone  4  to summing amplifier  21 , and the normally closed contacts  10   nc  are opened, breaking the connection between right microphone  3  and summing amplifier  21 . In this way, the signal from the left microphone  4  is used to drive both left speaker  8  and right speaker  7 , and the right microphone  3  is out of the circuit. The communicator can talk directly into the left microphone  4  in close proximity which increases the speech-to-noise signal ratio. 
         [0024]    Similarly, if the user  14  opts to push the right hand switch  9 , the normally open contacts  9   no  are closed routing the signal from right microphone  3  to summing amplifier  22 , and the normally closed contacts  9   nc  are opened, breaking the connection between left microphone  4  and summing amplifier  22 . In this way, the signal from the right microphone  3  is used to drive both left speaker  8  and right speaker  7 , and the left microphone  4  is out of the circuit. 
         [0025]    The switching logic in the example of this  FIG. 2  may be summarized in the following table 1: 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Switch Logic in Figure 2 
               
             
          
           
               
                   
                   
                 Neither 9 (R) 
                   
               
             
          
           
               
                   
                 Switch 
                 nor 10 (L) 
                 9 (R) 
                 10 (L) 
               
               
                   
                 Contact 
                 is operated 
                 Operated 
                 Operated 
               
               
                   
               
               
                   
                 9nc 
                 Closed 
                 Open 
                 Closed 
               
               
                   
                 9no 
                 Open 
                 Closed 
                 Open 
               
               
                   
                 10nc 
                 Closed 
                 Closed 
                 Open 
               
               
                   
                 10no 
                 Open 
                 Open 
                 Closed 
               
               
                   
               
             
          
         
       
     
         [0026]    It will be understood by one skilled in the art that the blocks in the block diagrams allow for variations and additions within the teachings of the invention. The amplifiers may be of any sort known in the art, the processors may include filtering, digital or analog audio shaping and other processing circuits as well as additional amplifiers or attenuators or controls, and the speakers may include audio transducers of any kind known to the art. The switches  9  and  10 , while drawn as simple multi-pole mechanical switches, may be implemented as fully solid-state circuits with touch actuators of any convenient sort. 
         [0027]      FIG. 3  shows an alternative embodiment of the switching system. In this embodiment, instead of completely muting the unselected microphone as described above, an attenuated signal from that microphone is still heard. To accomplish this, a second set of normally open contacts is added to each switch  9  and  10 , and a set of attenuators  36 ,  37 ,  38  and  39  are used. Attenuators  37  and  38  preferably have an attenuation of at least 6 dB, while attenuators  36  and  39  preferably have an attenuation between 0 dB and 6 dB. Left-side attenuators  36  and  38  have inputs coupled to left microphone  4 , with the output of attenuator  36  coupled to normally open contact  10   no - a  of left switch  10  and the output of attenuator  38  coupled to normally open contact  9   no - b  of right switch  9 . Right-side attenuators  37  and  39  have inputs coupled to right microphone  3 , with the output of attenuator  37  coupled to normally open contact  10   no - b  of left switch  10 , and the output of attenuator  39  coupled to normally open contact  9   no - a  of right switch  9 . The switching logic can thus be summarized in table 2, below: 
         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Switch Logic in Figure 3 
               
             
          
           
               
                   
                   
                 Neither 9 (R) 
                   
                   
               
               
                   
                 Switch 
                 nor 10 (L) 
                 9 (R) 
                 10 (L) 
               
               
                   
                 Contact 
                 is operated 
                 Operated 
                 Operated 
               
               
                   
               
               
                   
                 9nc 
                 Closed 
                 Open 
                 Closed 
               
               
                   
                 9no-a 
                 Open 
                 Closed 
                 Open 
               
               
                   
                 9no-b 
                 Open 
                 Closed 
                 Open 
               
               
                   
                 10nc 
                 Closed 
                 Closed 
                 Open 
               
               
                   
                 10no-a 
                 Open 
                 Open 
                 Closed 
               
               
                   
                 10no-b 
                 Open 
                 Open 
                 Closed 
               
               
                   
               
             
          
         
       
     
         [0028]    In the example shown in this  FIG. 3 , the output of processors  5  and  6  is sent to wireless transmitters  31  and  32  instead of speakers. Sometimes in very noisy environments, both earplugs and earcups are worn. The wireless transmitters  31  and  32  would transmit their signals to wireless earplugs  27  and  28  used by the user. Alternatively, the signals could be sent via wires to earplugs with speakers in them. 
         [0029]    In this embodiment, under normal operation when neither right switch  9  nor left switch  10  is operated, normally closed contacts  9   nc  and  10   nc  are closed and the system operates in stereo. That is, the audio output of right microphone  3  is coupled through normally closed contacts  10   nc  to an input of summing amplifier  33 , the output of which is coupled to processor  5 , and the processed output is sent to wireless transmitter  31 . Similarly, the audio output of left microphone  4  is coupled through normally closed contacts  9   nc  to an input of summing amplifier  34 , then to processor  6  and to wireless transmitter  32 . 
         [0030]    When the left switch  10  is pressed, the left microphone  4  remains connected through normally closed contacts  9   nc  of the right switch  9  to an input of summing amplifier  34 , then to processor  6  and to wireless transmitter  32 . The normally closed contacts  10   nc  open, disconnecting the full output of right microphone  3  from summing amplifier  33 . Normally open contacts  10   no - a  and  10   no - b  close, which causes the attenuated signal from the right microphone  3 —that is, the output of attenuator  37 —and an attenuated signal from left microphone  4 —that is, the output of attenuator  36 —to be combined in summing amplifier  33 . The combined attenuated signals are then coupled to processor  5  and output to transmitter  31 . Thus, the full audio from the left microphone  4  appears on the left earphone  28  (received from left transmitter  32 ), and the right earphone  27  (received from right transmitter  31 ) receives a mixture of attenuated signals from both the right microphone  3  and the left microphone  4 . 
         [0031]    The operation when the right switch  9  is pressed is the reverse of that described above. The right microphone  3  remains connected through normally closed contacts  10   nc  of the left switch  10  to an input of summing amplifier  33 , then to processor  5  and to wireless transmitter  31 . The normally closed contacts  9   nc  open, disconnecting the full output of left microphone  4  from summing amplifier  34 . Normally open contacts  9   no - a  and  9   no - b  close, which causes the attenuated signal from the left microphone  4 —that is, the output of attenuator  38 —and an attenuated signal from right microphone  3 —that is, the output of attenuator  39 —to be combined in summing amplifier  34 . The combined attenuated signals are then coupled to processor  6  and output to transmitter  32 . Thus, the full audio from the right microphone  3  appears on the right earphone  27  (received from right transmitter  31 ), and the left earphone  28  (received from left transmitter  32 ) receives a mixture of attenuated signals from both the right microphone  3  and the left microphone  4 . 
         [0032]    The arrangement of  FIG. 3  allows the user to maintain acoustic directional cues, by retaining some of the unselected audio in the unselected ear. 
         [0033]    In another embodiment of the invention, shown in  FIG. 4 , when switch  9  or  10  is pressed, not only does the channel switching occur, but the signal is processed for better speech intelligibility. In this example, electronic switching is shown rather than the multi-contact switches shown in the previous examples. The right switch  9  and left switch  10  activate electronics in logic module  40  which converts the key presses into outputs R and L (for right and left switch operation, respectively) with the proper logic levels for the switching circuitry. The audio from right microphone  3  is optionally routed through pre-processing circuitry  41  to switches  47  and  48 . The output of switch  47  is fed to an input of summing amplifier  21 , and the output of switch  48  is processed in right speech enhancing circuit  43 , and then fed to another input of summing amplifier  21 . As in the embodiment of  FIG. 1 , the output of summing amplifier  21  is further amplified and, optionally filtered or otherwise processed in processor  5 , and the amplified signal is fed to right speaker  7 . The left side  3  operates similarly—audio signals from left-side microphone  4  are optionally routed through pre-processing circuitry  42  to switches  49  and  50 . The output of switch  50  is fed to an input of summing amplifier  22 , and the output of switch  49  is processed in left speech enhancing circuit  44 , and then fed to another input of summing amplifier  22 . As in the embodiment of  FIG. 1 , the output of summing amplifier  22  is further amplified and, optionally filtered or otherwise processed in processor  6 , and the amplified signal is fed to left speaker  8 . Switch  51  acts to combine the outputs of summing amplifiers  21  and  22 , so that when switch  51  is closed both processors  5  and  6  are fed with the same audio signal. 
         [0034]    Pre-processing electronics blocks  41  and  42  account for any equalization and compression that may be used as well as other processing electronics commonly used in audio systems. 
         [0035]    The speech-enhancement circuitry  43  and  44  can be something as simple as speechband filters—that is, a high-pass filter combined with a low-pass filter designed to pass frequencies within the speech band while attenuating frequencies outside of the speech band. The speech-enhancement circuitry could employ other speech-enhancement techniques as well. 
         [0036]    The switches  47 ,  48 ,  49 ,  50  and  51  are operated by the L and R signals from logic circuit  40 , in combination with NOR gate  45  and inverter  46 . Specifically, the inputs to NOR gate  45  are L and R, and the output is NOT (L OR R)—that is, the output of the NOR gate is active when neither L nor R is active (i.e. neither switch is operated). The output of NOR gate  45  operates switches  47  and  50 , and is input to inverter  46 . The output of inverter  46  is the inverse of the output of NOR gate  45 —that is, it is active when either L or R is active (i.e. either switch is operated)—and operates switch  51 . Switch  48  is operated by R (i.e. closed when right switch  9  is operated), and switch  49  is operated by L (i.e. closed when left switch  10  is operated). This can be summarized in the following table 3: 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Switch Logic in Figure 4 
               
             
          
           
               
                   
                 Neither 9 (R) 
                   
                   
               
               
                   
                 nor 10 (L) 
                 9 (R) 
                 10 (L) 
               
               
                 Switch 
                 is operated 
                 Operated 
                 Operated 
               
               
                   
               
             
          
           
               
                 47 
                 Closed 
                 Open 
                 Open 
               
               
                 48 
                 Open 
                 Closed 
                 Open 
               
               
                 49 
                 Open 
                 Open 
                 Closed 
               
               
                 50 
                 Closed 
                 Open 
                 Open 
               
               
                 51 
                 Open 
                 Closed 
                 Closed 
               
               
                   
               
             
          
         
       
     
         [0037]    In this embodiment, under normal operation when neither right switch  9  nor left switch  10  is operated, switches  47  and  50  are closed and the system operates in stereo. That is, the audio output of right microphone  3  is coupled through switch  47  to an input of summing amplifier  21 , the output of which is coupled to processor  5 , and the processed output is sent to speaker  7 . Similarly, the audio output of left microphone  4  is coupled through switch  50  to an input of summing amplifier  22 , then to processor  6  and to speaker  8 . 
         [0038]    When the left switch  10  is pressed, L is active, closing switch  49  and causing the output of NOR gate  45  to be inactive, which opens switches  47  and  50  and closes switch  51 . The left microphone  4  is thus connected through switch  49  to left speech-enhancement circuitry  44 , and, with switches  48  and  50  open, the right microphone  3  is disconnected from summing amplifier  21 . Switch  51  connect the outputs of summing amplifiers  21  and  22  together, so that the signal from the left microphone  4  is routed to both the left  6  and right  5  processors and left  8  and right  7  speakers. 
         [0039]    The operation when the right switch  9  is pressed is the reverse of that described above—R is active, closing switch  48  and causing the output of NOR gate  45  to be inactive, which opens switches  47  and  50  and closes switch  51 . The right microphone  3  is thus connected through switch  48  to right speech-enhancement circuitry  43 , and, with switches  49  and  50  open, the left microphone  3  is disconnected from summing amplifier  22 . Switch  51  connect the outputs of summing amplifiers  21  and  22  together, so that the signal from the right microphone  3  is routed to both the left  6  and right  5  processors and left  8  and right  7  speakers. 
         [0040]    The switching system can be used on helmets, headsets, and in-ear communications devices as well as other devices. As noted above, the left  10  and right  9  switches can be located on the earcups, helmets, earplug earshells, cables, or an electronics box worn on a belt among other locations. 
         [0041]    Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.