Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R1/00—Details of transducers, loudspeakers or microphones
  • H04R1/46—Special adaptations for use as contact microphones, e.g. on musical instrument, on stethoscope

Definitions

• This invention relates to a communications system and more particularly to a system for voice transmission.
• Voice transmitting systems employ a microphone, that is to say a transducer whereby sound waves are caused to generate or modulate an electrical signal.
• the microphone is connected to the input side of a circuit which transmits the >electrical signal by wire or wireless means to a receiver.
• a telephone is an example of a voice transmitter in which the voice of a person speaking is detected by a microphone, the microphone signal is amplified and then delivered to a receiver comprising the earphone of a listener.
• Commonly used radio transceivers provide a voice transmitting system on which the voice of a person speaking is detected by a microphone adapted to modulate the, frequency or amplitude of a radio signal which may be detected by a receiver.
• a person wearing a respirator or other mask is unable to communicate by microphone unless the microphone is incorporated within the mask adding substantially to the cost of the mask and often making the mask bulkier than need be since the microphone must be spaced from the mouth.
• the present invention consists in a voice transmitting system comprising: a microphone having a high impedance as herein defined; earplug means adapted to hold the microphone in or adjacent an outer ear of a person so as substantially to enclose air between the microphone and the tympanic membrane of the ear, and a circuit for transmitting a signal produced or modulated by the microphone in response to sound waves, if any, which are transmitted via the persons oto-laryngeal system to the tympanic membrane and propogated in the enclosed air.
• high impedance is meant that the microphone has an impedance equivalent to at least 1000 ohms, and preferably greater than 2000 ohms at 1kHz.
• the microphone is worn by means of an earplug individually cast for the ear of the wearer in the manner of a hearing aid earplug and is a transducer which is also operable as an earphone.
• the present invention is based on the surprising discovery that when air is enclosed between the tympanic membrane and a sufficiently high impedance microphone, the effect of external noise and vibration is greatly - reduced, and in preferred embodiments, is halved.
• a low impedance (400-800 ohms) transducer is employed as a microphone a high proportion of the detected audio energy is transmitted via bone structure and is thus subjected to noise vibrations from the general environment. It has been found that when a high impedance microphone is employed in accordance with the present invention, a high proportion of the detected audio energy is substantially transmitted from the tympanic membrane by means of the air column in the auditory canal and is much less influenced by vibrations in the bone which originate externally.
• FIG. 1 circuit schematic diagram
• the circuit is an interface circuit for use with a two way radio transceiver (not shown) having connectors for external speaker and microphone.
• the interface circuit of Fig. 1 comprises a high impedance transducer T, a two stage amplifier and an electronic switch and is powered by a 1.5 V battery.
• C- In use terminal Al is connected to the audio output of the radio transceiver.
• transducer T When ganged switch SIB is in the "NC" position as shown in Fig. 1 an audio signal from the transceiver connected at the "audio-in” terminal Al is routed to transducer T via capacitor C8 and resistor Rll.
• Capacitor C8 provides DC blocking and resistor R7 provides overload protection for transducer T which is a type AP2000 earpiece supplied by Crystal Aid Pty. Ltd., Australia, having an impedance of around 2000 ohms at 1kHz and developed for use as a hearing aid.
• the audio signal is then attenuated to the required level by variable resistance RV1 and fed to the associated transceiver via terminal A2 "audio out".
• Earpiece- T comprises a high impedance coil having a DC resistance of about 2000 ohms and preferably higher and has a magnet moveable relative to the coil by a diaphram affixed either to the magnet or the coil.
• the "earpiece” is thus able to function either as a microphone to modulate a signal in response to movement of the diaphram or as an earphone when fed with a modulated signal.
• the "earpiece” is of a size similar to a hearing aid earpiece and is held in the ear of a wearer by a custom made hollow casting such as is often used to seal a hearing aid earphone to an ear.
• the earpiece may be otherwise adapted by shape to fit in or adjacent the ear so as to enclose air between the transducer and tympanic membrane.
• Switch SW1 serves to disconnect the audio reception line from the transceiver to the transducer when the transducer is used for voice transmission. Because the apparatus operates from a 1.5 battery it is non-sparking and useable in hazardous environments.
• Fl is a ferrite bead providing shielding.
• Ql, Q2 and Q3 are each type BC 549 transistors.
• the circuit - parameters shown in Fig. 1 and indeed the circuit itself may be varied in ways which will be apparent to those skilled in the art from the teaching hereof.
• the interface circuit is adapted to be worn on the belt.
• ear protectors if desired, may be worn over the earpiece to further reduce extraneous noise.
• the microphone is built into ear protectors.

Landscapes

• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Headphones And Earphones (AREA)
• Details Of Audible-Bandwidth Transducers (AREA)
• Reduction Or Emphasis Of Bandwidth Of Signals (AREA)
• Silicates, Zeolites, And Molecular Sieves (AREA)
• Telephone Set Structure (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=3769456

Family Applications (1)

Country Status (5)

Families Citing this family (7)

Family Cites Families (4)

• 1983
  • 1983-03-31 AU AU13770/83A patent/AU552678B2/en not_active Ceased
  • 1983-03-31 WO PCT/AU1983/000039 patent/WO1983003733A1/fr not_active Application Discontinuation
  • 1983-03-31 EP EP19830901058 patent/EP0114828A4/fr not_active Withdrawn
  • 1983-03-31 JP JP58501137A patent/JPS59500744A/ja active Pending
  • 1983-04-05 CA CA000425177A patent/CA1200006A/fr not_active Expired

Non-Patent Citations (1)

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