Abstract:
Hearing protectors protect the ears of its user by providing high attenuation of surrounding noise. However, nearby warning signals and speech sounds are being attenuated together with the noise. Conventional muff-type talk-through hearing protectors uses a combination of external microphones, limiting amplifier, built-in speakers and muff-type hearing protectors to reduce the intensity of external noise to a safe level, allowing the user to hear external sounds. However, these headphone-type muffs impede its use together with other head-mounted protective equipment. Audio input from a bone vibrator to a user is carried by a combination of vibrations in the skull bones and inter-cranial fluids directly to the cochlea of the inner ear. Bone vibrators are inherently safe, as higher driving voltage also does not translate to a higher output. A bone vibrator is used in tandem with an amplified microphone and an in-ear-type hearing protection apparatus. Output from the primary amplified microphone can be attenuated when sound levels become excessive, allowing a user to continue hearing the surrounding conversations in the noise.

Description:
FIELD OF INVENTION  
       [0001]     The present invention relates generally to a talk-through system. In particular, the invention relates to a vibration-based talk-through apparatus.  
       BACKGROUND  
       [0002]     In a noise-filled environment, hearing protectors are used to protect the ears of its user. Earplugs, muff type circum-aural ear cups and the like hearing protectors, provide good hearing protection when properly worn. These hearing protectors provide high attenuation of surrounding noise. Active noise canceling devices further reduce the low frequency noise that the hearing protectors are unable to alleviate.  
         [0003]     A hearing protector isolates its user from the environment in the acoustic domain. In environments where physical dangers are imminent, nearby voices, warning signals and sounds are being attenuated together with the noise. Ironically, the use of hearing protectors to protect the sense of hearing of its user may compromise the physical safety of the user in the process.  
         [0004]     Various muff-type electronic hearing protectors use a combination of external microphones, limiting amplifiers and built-in speakers to introduce sound while controlling the intensity of external noise to a safe level. This allows the user to hear external sounds. These hearing protectors are conventionally known as active, electronic or talk-through hearing protectors because the user can hear speech through the hearing protectors.  
         [0005]     However, these active hearing protectors require the use of headphone type muffs that impedes its use in conjunction with headgears, protective helmets, breathing apparatus and the like head-mounted gears. Moreover, these active hearing protectors cannot be used effectively with ear-plugs. This reduces the usefulness of these active hearing protectors for firefighters, construction workers and the like high noise environment operators or workers as the active hearing protectors cannot be used together with other respective head and respiratory protection equipment.  
         [0006]     Since the speakers used in the active hearing protectors are capable of producing sound at a level in excess of 120 dB, limiting amplifiers are required to avoid transmitting hazardous sound levels to the ear. In the event of amplifier failure, this further exposes the ear to an inherently unsafe device, the speaker.  
         [0007]     Hence, this clearly affirms a need for a better talk-through apparatus that addresses the foregoing problems.  
       SUMMARY  
       [0008]     Embodiments of the invention are based on the principle that audio input from a bone vibrator to a user is conducted by a combination of vibrations in the skull bones and inter-cranial fluids directly to the cochlea of the inner ear.  
         [0009]     Conventional bone vibrators, which are also known as bone conduction transducers, are generally unable to transmit beyond 80-85 dB with reference to the sound pressure level of the inner ear. This places the output of bone vibrators within the “safe range” for continuous exposure of the ear to bone vibrator outputs. Attempts have been made to increase the output of a bone vibrator by increasing the driving voltage of the bone vibrator. However, the output of the bone vibrator becomes non-linear when a higher driving voltage is introduced. The higher driving voltage provided to the bone vibrator translates into vibrations that lift the bone vibrator off the skin of the user (i.e. similar to a jumping-effect). However, irritation from these high vibration levels are localised at the point where the bone vibrator comes into contact with the skin of the user. Hence, this shows that bone vibrators are inherently safe.  
         [0010]     A bone vibrator is used in tandem with an amplified microphone and in-ear-type earplugs to provide a talk-through system. When deployed in an acoustic-hazardous environment, output from the amplified microphone can be attenuated when high sound levels lead to minor discomfort. This can be accomplished either by a conventional analogue compression amplifier or by a digital noise reduction element. This not only avoids distortion from the bone vibrator output, but also allows a user to continue hearing the surrounding conversations in the noise.  
         [0011]     The talk-through system can be further coupled to a radio transmitter, a signal set, a receiver to function as a vibration-based communication system.  
         [0012]     In accordance with a first aspect of the invention, there is disclosed a vibration-based talk-through apparatus for facilitating talk-through for a user using a hearing protection system, the vibration talk-through system comprising: 
        a microphone assembly, the microphone assembly comprising: 
            a first microphone receiving ambient sounds from the surrounding environment; and     a circuitry being electrically connected to the first microphone, the first microphone converting the ambient sounds received from the surrounding environment into ambient electrical signals, the circuitry amplifying the received ambient electrical signals and transmitting the amplified ambient electrical signals to the bone vibrator;    
            a bone vibrator disposable onto the skin covering a cranial bone of a user, the bone vibrator converting the amplified ambient electrical signals received from the circuitry into vibrations, the bone vibrator being coupled to the microphone assembly, the cranial bone conducting the vibrations to the cochlea of an inner ear of the user;     a hearing protection apparatus, the hearing protection apparatus being detachably coupled to the vibrator assembly, and the hearing protection apparatus substantially preventing sound from being transmitted to the inner ear of a user through the ear canal; and     a positioning means for mounting to an outer ear of the user the hearing protection apparatus in tandem with the positioning of the bone vibrator onto the cranial bone, and the hearing protection apparatus substantially preventing sound from being transmitted to the corresponding inner ear of the user through the ear canal,     wherein the bone vibrator is positionable onto the cranial bone in a manner that use of the hearing protection system is not substantially impeded.        
 
         [0020]     In accordance with a second aspect of the invention, there is disclosed a method for providing vibration-based talk-through hearing protection, comprising the steps of: 
        disposing a hearing protection apparatus in relation to an outer ear of a user for substantially preventing sound from reaching the inner ear of a user through the outer ear;     receiving ambient sounds from the surrounding environment into a first microphone, the first microphone converting the ambient sounds received into ambient electrical signals;     amplifying the ambient electrical signals received from the first microphone, the ambient electrical signals being amplified by a circuitry, and the circuitry being electrically connected to the first microphone;     locating the bone vibrator onto the skin covering a cranial bone of the user, the cranial bone conducting the vibrations produced by the bone vibrator to the cochlea of the ear; and     transmitting the amplified ambient electrical signals to a bone vibrator, the bone vibrator converting the amplified ambient electrical signals into vibrations, the bone vibrator being electrically connected to the circuitry,     wherein the user is able to hear ambient sounds from the surrounding environment with the ear protected by the hearing protection apparatus.       
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     Embodiments of the invention are described hereinafter with reference to the following drawings, in which:  
         [0028]      FIG. 1  shows a perspective view of a vibration-based talk-through apparatus;  
         [0029]      FIG. 2  shows a perspective view of the vibration-based talk-through apparatus  FIG. 1  with a second microphone supported by a boom; and  
         [0030]      FIG. 3  shows a perspective view of the vibration-based talk-through apparatus in  FIG. 1  with a contact-based transducer attached to a cable.  
     
    
     DETAILED DESCRIPTION  
       [0031]     A vibration-based talk-through apparatus for addressing the foregoing problems is described hereinafter.  
         [0032]     A first embodiment of the invention, a vibration-based talk-through apparatus  20  as shown in  FIG. 1 ; includes a C-shaped headband  22  for extending around the neck of a user. The headband  22  has a first end  24  and an opposed second end  26 . The headband  22  is resiliently biased for fitting heads of various girths.  
         [0033]     A first ear-hook assembly  28  and second ear-hook assembly  30  is coupled to the first end  24  and second end  26  of the headband  22  respectively. Each ear-hook assembly  28 / 30  includes an ear-hook  32 , a bone vibrator  34  (not shown) placed inside a vibrator housing  36  and a holder  38 . The ear-hook  32  is substantially shaped and dimensioned to conform to the outer periphery of an ear of a user. The ear-hook  32  extends over the superior periphery of the ear of the user. The bone vibrator  34  is positioned above the temporal bone. The bone vibrator  34  converts any received electrical signals into vibrations. The temporal bone conducts vibrations generated by the bone vibrator  34  and transmits the vibrations to the ear of the user.  
         [0034]     The vibrator housing  36  is shaped and dimensioned to accommodate the bone vibrator  34  within. The holder  38  extends from the ear-hook  32  to the vibrator housing  36 .  
         [0035]     The holder  38  extends along a portion of the inferior periphery of the ear of the user. The holder  38  positions the bone vibrator  34  onto the temporal bone. The ear-hook  32  permits easy removal of the vibration-based talk-through apparatus  20  from the head of the user. This also facilitates the easy wearing of the vibration-based talk-through apparatus  20  onto the head of the user as the ear-hook assembly  28 / 30  acts to locates the bone vibrator  34  onto the temporal bone and holds the bone vibrator  34  firmly in place. The first microphone  42  is preferably located far from the mouth of the user for substantially reducing speech sounds from being picked up by the first microphone  42 .  
         [0036]     A microphone assembly  40  is detachably coupled to the headband  22  and includes a first microphone  42 , a circuitry  44  (not shown) and a microphone housing  46 . The first microphone  42  receives ambient sounds from the surrounding environment. The first microphone  42  is electrically connected to the circuitry  44 . The first microphone  42  converts ambient sounds received into ambient electrical signals. The ambient electrical signals are then transmitted to the circuitry  44 . The circuitry  44  amplifies the received ambient electrical signals and transmits the amplified ambient electrical signals to the bone vibrator  34 . The microphone housing  46  is shaped and dimensioned to house both the first microphone  42  and the circuitry  44 . The microphone housing  46  is coupled to the headband  22 . The bone vibrator  34  is electrically connected to the circuitry  44 .  
         [0037]     The circuitry  44  is an active circuitry which has a frequency response of preferably from 400 Hz to 4 kHz. A battery supplies power to the circuitry  44 . The microphone housing  46  is further shaped and dimensioned to house the battery.  
         [0038]     The circuitry  44  includea compression amplifier (not shown) for scaling the level of ambient electrical signals below a pre-determined level for transmission to the bone vibrator  34 . The scaling of the level of ambient electrical signals substantially reduces distortion at the bone vibrator  34  when a high level of ambient sound is received by the first microphone  42 .  
         [0039]     The circuitry  44  includes a noise reduction element (not shown) having a limiting level which is pre-determined. The noise reduction element passing ambient electrical signals having levels not exceeding the limiting level to the circuitry  44  for amplification, and rejecting ambient electrical signals having levels exceeding the limiting level.  
         [0040]     The first embodiment of the invention, the vibration-based talk-through apparatus  20 , is used in tandem with a hearing protection apparatus  48 . The bearing protection apparatus  48  is preferably an in-ear-type apparatus that functions to impede sound from being transmitted to the inner ear of the user through the ear canal and therefore provides hearing protection. However, the hearing protection apparatus  48  can also be either a super-aural or a circum-aural (i.e. muff-type) hearing protection apparatus. The vibration-based talk-through apparatus  20  allows speech, warning signals and ambient sounds in the frequency range of 400 Hz to 4000 kHz to be transmitted to the user.  
         [0041]     The ear-hook  32  is shaped allow access to the outer ear. This allows the hearing protection apparatus  48  to be easily inserted into or removed from the ear canal without removing the vibration-based talk-through apparatus  20  from the head of the user. Preferably, the hearing protection apparatus  48  is detachably coupled to the vibrator assembly  36  using lengths of strings. The stings prevent the misplacing of the hearing protection apparatus  48  when it is removed from the ear of the user.  
         [0042]     A second embodiment of the invention, a vibration-based talk-through apparatus  20  as seen in  FIG. 2 , comprises of eight main elements: a headband  22 , a first ear-hook assembly  28 , a second ear-hook assembly  30 , a bone vibrator  34 , a vibrator housing  36 , a microphone assembly  40 , a first microphone  42  and a hearing protection apparatus  48 . The descriptions in relation to the structural configurations of and positional relationships among the components described in the first embodiment of the invention with reference to  FIG. 1  are incorporated herein. The microphone assembly  40  and the headband  22  are interconnected by a short length of wire.  
         [0043]     An I/O (input/output) adapter  50  is electrically connected to the circuitry  44 . An extendible cable  52  extends from the microphone assembly  40  to the I/O adapter  50 . The I/O adapter  50  is coupled to a transceiver  54 . The transceiver  54  transmits and receives electrical signals via radio waves for facilitating radio communications with a base station.  
         [0044]     The transceiver  54  converts first speech electrical signals received from the circuitry  45  into radio waves for transmission. The transceiver  54  also receives radio waves and converts into second speech electrical signals for transmission to the circuitry  45 . By doing so, the transceiver  54  facilitates radio communications between the user of the vibration-based communication systems and users of other communication systems.  
         [0045]     The circuitry  45  mixes ambient electrical signals received from the first microphone  42  with second speech electrical signals received from the transceiver  54 . The circuitry  44  amplifies the mixed electrical signals and transmits the amplified electrical signals to the bone vibrator  34 .  
         [0046]     However, it is preferred that the circuitry  45  prevents ambient electrical signals received from the first microphone  42  from being transmitted to the bone vibrator  34  when second speech electrical signals are received from the transceiver  54  by performing switching operations. The circuitry  45  amplifies the second speech electrical signals received from the transceiver  54  and transmits the amplified second speech electrical signals to the bone vibrator  34 .  
         [0047]     Alternatively, the circuitry  45  prevents second speech electrical signals received from the transceiver  54  from being transmitted to the bone vibrator  34  when ambient electrical signals are received from the first microphone  42  by performing switching operations. The circuitry  45  amplifies the ambient electrical signals received from the first microphone  42  and transmits the amplified ambient electrical signals to the bone vibrator  34 .  
         [0048]     A primary cable  56  extends from the microphone assembly  40  to the first ear-hook assembly  28 . The primary cable  56  provides dexterity to the microphone assembly  40 . The first microphone  42  remains electrically connected to the circuitry  4 S.  
         [0049]     A second microphone  58  (not shown) is electrically connected to the circuitry  45 . The second microphone  58  converts articulated sounds received from the user into first speech electrical signals by being positioned near the mouth of the user. These first speech electrical signals are then transmitted to the circuitry  45 . A microphone windscreen  60  is shaped and dimensioned to cover the second microphone  58 . A boom  62  has a first end  64  that is coupled to either first or second ear-hook assembly  28 / 30  and an opposing second end  66  that is coupled to the second microphone  58 . The second end  66  of the boom  62  is adjustable for positioning the second microphone  5 S in front of the mouth. The second microphone  58  is preferably a noise cancelling microphone for cancelling noise and ambient sounds.  
         [0050]     A switch  68 , preferably a PTT (push-to-talk) switch, has two states: an ACTIVATED state and an INACTIVATED state. The switch  68  is coupled to the circuitry  45 . In the ACTIVATED state, the circuitry  44  amplifies the first speech electrical signals received from the second microphone  58  and transmits the amplified first speech electrical signals to the transceiver  54 . In the INACTIVATED state, the circuitry  44  prevents the transmission of first speech electrical signals received from the second microphone  58  to the transceiver  54 .  
         [0051]     A third embodiment of the invention, a vibration-based talk-through apparatus  20  as seen in  FIG. 3 , comprises of nine main elements: a headband  22 , a first ear-hook assembly  28 , a second ear-hook assembly  30 , a bone vibrator  34 , a microphone assembly  40 , a first microphone  42 , a hearing protection apparatus  48  an I/O adapter  50 , and a transceiver  54 . The descriptions in relation to the structural configurations of and positional relationships among the components described in the second embodiment of the invention with reference to  FIG. 2  are incorporated herein, with the exception that three elements: a second microphone  58 , a microphone windscreen  60 , and a boom  62 , which are correspondingly replaced by a contact-based transducer  70  (not shown), a transducer housing  72  and a secondary cable  74  in the third embodiment. These replacements are preferable in situations where a breathing apparatus is used.  
         [0052]     The contact-based transducer  70  is electrically connected to the circuitry  45 . The contact-based transducer  70  converts vibrations received from the skull of a user into first speech electrical signals. These first speech electrical signals are transmitted from the contact-based transducer to the circuitry  45 . The transducer housing  72  is shaped and dimensioned to house the contact-based transducer  70 . The transducer housing  72  is preferably flexible to allow it to conform to the outer periphery of the posterior region of a human skull and allow for attachment thereto. The secondary cable  74  extends from the transducer housing  72  to the microphone assembly  40 . The secondary cable  74  has substantial length and flexibility to allow the contact-based transducer  70  to be placed anywhere on the skull of a human. The contact-based transducer  70  does not pick up ambient sounds and speech.  
         [0053]     A switch  68 , preferably a PTT (push-to-talk) switch, has two states: an ACTIVATED state and an INACTIVATED state. The switch  68  is coupled to the circuitry  45 . In the ACTIVATED state, the circuitry  45  amplifies the first speech electrical signals received from the contact-based transducer  70  and transmits the amplified first speech electrical signals to the transceiver  54 . In the INACTIVATED state, the circuitry  45  prevents the transmission of first speech electrical signal signals received from the contact-based transducer  70  to the transceiver  54 .  
         [0054]     The sealed construction of the first ear-hook assembly  28 , the second ear-hook assembly  30  and the microphone assembly allows the first, second and third embodiments of the invention, the vibration-based talc-through apparatus  20  to be water-resistant to a certain depth.  
         [0055]     In the foregoing manner, a vibration-based talk-through apparatus is described according to three embodiments of the invention for addressing the foregoing disadvantages of conventional vibration-based talk-through apparatus. Although only three embodiments of the invention are disclosed, it is apparent to one skilled in the art in view of this disclosure that numerous changes and/or modification can be made without departing from the scope and spirit of the invention.