EP0390758A2 - Amplificateur pour microphone de contact - Google Patents

Amplificateur pour microphone de contact Download PDF

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Publication number
EP0390758A2
EP0390758A2 EP90850090A EP90850090A EP0390758A2 EP 0390758 A2 EP0390758 A2 EP 0390758A2 EP 90850090 A EP90850090 A EP 90850090A EP 90850090 A EP90850090 A EP 90850090A EP 0390758 A2 EP0390758 A2 EP 0390758A2
Authority
EP
European Patent Office
Prior art keywords
amplitude
signal
modifying
output signal
contact microphone
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP90850090A
Other languages
German (de)
English (en)
Other versions
EP0390758A3 (fr
Inventor
Leif Palmaer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0390758A2 publication Critical patent/EP0390758A2/fr
Publication of EP0390758A3 publication Critical patent/EP0390758A3/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • 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

  • the present invention relates to a method and a device for improving the clarity of speech recorded using a contact microphone.
  • contact micro­phones In environments with a high noise level, e.g. certain types of aircraft, ships and land vehicles, contact micro­phones have long been used instead of normal acoustic microphones in order to avoid the speech recorded being drowned by disturbing background noise.
  • the most usual type of contact microphone is the throat microphone or laryngo­phone, although other types do exist. Characteristic of all these contact microphones is that, if speech or other sound is to be picked up it must be in the form of applied mechanical vibration. This means that a contact microphone must always be located in direct contact with the user's throat or head.
  • the speech recorded from a contact microphone is always relatively incomplete and un­articulated. Furthermore, it contains hardly any of the harmonics which in normal speech are derived from resonance phenomena in the mouth and nasal cavity and which are of vital significance to clarity. Besides this poor ability to record speech there are several other factors entailed in the use of contact microphones which have a negative effect on the clarity of recorded speech. In the first place the transfer from user to microphone may vary greatly due to variations in the quality of the mechanical contact between microphone and user.
  • the level of the electric signal generated by a contact microphone is usually so low that it requires considerable amplification, thus causing noise both from the microphone itself and from the subsequent amplification stage.
  • the object of the present invention is to achieve a method and a device for improving the clarity of speech recorded using a contact microphone whereby the above disadvantages of contact microphones are considerably reduced.
  • the method proposed according to the invention to achieve this object is primarily characterised in that the electric output signal from the contact microphone, preferably after amplification and possibly some other form of processing, is subjected to a treatment for modifying its amplitude whereby, if its amplitude reaches or exceeds a predetermined lower limit value, it is amplified to form an amplified signal having a higher amplitude, said amplitude being substantially independent of the first-mentioned amplitude, whereas if its amplitude is below said limit value, it is instead suppressed and prevented from being transmitted further.
  • the treatment of the output signal from the contact micro­phone described above enables a substantially constant signal level to be obtained, which is substantially independent of variations in the strength of the speech picked up by the microphone. Furthermore, if the value of said predetermined lower limit is selected in suitable manner, it is possible to effectively suppress both all disturbing sounds and electronic noise during pauses in the speech.
  • the limit value may advantageously be adjustable to permit adjustment to a specific user of the microphone and to the specific environment in which it is to be used.
  • the amplitude of the amplified signal may preferably also be adjustable to allow for adjustment to the equipment which is to receive the signal.
  • the output signal from the contact microphone is also subjected to a treatment for modifying its spectral structure.
  • This treat­ment preferably carried out subsequent to the previously mentioned treatment of the signal for modifying its ampli­tude, may be performed so that components in the signal which represent sounds having a frequency lying outside a predetermined speech frequency range, are powerfully dampened or completely eliminated. In this way, disturbances occurring in the signal which derive from foreign sources of sound or from electronic noise will also be suppressed while speech is in the process of being transmitted.
  • the above-mentioned treatment of the output signal from the contact microphone, intended to modify the spectral structure of the signal can also be designed in such a manner that the processed signal will acquire a structure corresponding better to the spectral structure of natural acoustic speech than the original output from the micro­phone.
  • the spectral treatment of the output signal from the microphone may suitably comprise filtration of the signal.
  • This filtration should suitably be performed in the manner of band pass filtration. It may also be performed so that components lying within the relevant pass band and having higher frequency are given preference over components with lower frequency.
  • the spectral treatment of the output signal from the microphone may comprise the generation of harmonics for fundamentals included in this signal.
  • a contact microphone e.g. a throat microphone.
  • the microphone 10 is connected to the input of an amplifier 11, the output of which is connected to the input of a signal processor 12.
  • the signal processor 12 may in principle consist of an amplifier with an amplification factor which varies in such a manner dependent on the amplitude of its input signal that, if the amplitude of the input signal reaches or exceeds a predetermined lower limit value, it will generate an output signal having a predetermined higher amplitude, said amplitude being substantially independent of the amplitude of the signal received, whereas if the amplitude of the signal received is below said limit value, no output signal will be transmitted.
  • the unit 12 thus operates as an amplifier, the amplification factor of which is greater than 1, preferably much greater than 1, if the amplitude of the output signal from the pre-amplifier 11 is higher than the predetermined limit value, but much less than 1, preferably 0, if the amplitude of the output signal from the pre-amplifier is lower than said limit value.
  • the output of the unit 12 is connected to the input of an additional signal processor 13 arranged to generate an output signal having a spectral structure which is modified in relation to the signal received by this unit and which agrees better than the signal received, with the spectral structure of natural acoustic speech.
  • the unit 13 may include filtering means to filter off those components in the signal received which have a frequency outside a predetermined speech frequency range. These filter means may consist of a band pass filter.
  • the unit 13 may also comprise means for generating harmonics for fundamentals included in the signal received.
  • the previously mentioned filtering means may consist of a high pass filter having a relatively low limit frequency arranged before the harmonics-generating, and a low pass filter having a relatively high limit frequency arranged after the harmonics-generating means.
  • the final stage 14 designates a final stage following the unit 13, via which the output signal from the unit 13 can be supplied to the output 15 of the device.
  • the final stage 14 may fulfil various desired functions. It may, for instance, provide the necessary interface to the circuits to which the output 15 is to be connected. It may also form a gain amplifier.
  • Means serving to modify the spectral structure of the output signal from the contact microphone may also be arranged in front of the unit 12, for example.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Details Of Audible-Bandwidth Transducers (AREA)
  • Circuit For Audible Band Transducer (AREA)
EP19900850090 1989-03-06 1990-03-05 Amplificateur pour microphone de contact Withdrawn EP0390758A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8900759 1989-03-06
SE8900759A SE466377B (sv) 1989-03-06 1989-03-06 Saett och anordning foer att foerbaettra uppfattbarheten hos med hjaelp av en kontaktmikrofon upptaget tal

Publications (2)

Publication Number Publication Date
EP0390758A2 true EP0390758A2 (fr) 1990-10-03
EP0390758A3 EP0390758A3 (fr) 1991-11-13

Family

ID=20375235

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900850090 Withdrawn EP0390758A3 (fr) 1989-03-06 1990-03-05 Amplificateur pour microphone de contact

Country Status (2)

Country Link
EP (1) EP0390758A3 (fr)
SE (1) SE466377B (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2334174A (en) * 1998-02-06 1999-08-11 Rajiv Maraj Electronic stethoscope

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2016248A (en) * 1978-03-10 1979-09-19 Dbx Detection and monitoring device
US4288753A (en) * 1978-09-12 1981-09-08 Nippon Electric Company, Ltd. Muting circuit with operational amplifier
EP0201421A1 (fr) * 1985-05-02 1986-11-12 Societe Industrielle De Liaisons Electriques - Silec Capteur microphonique de contact à membrane piézo polymère

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2016248A (en) * 1978-03-10 1979-09-19 Dbx Detection and monitoring device
US4288753A (en) * 1978-09-12 1981-09-08 Nippon Electric Company, Ltd. Muting circuit with operational amplifier
EP0201421A1 (fr) * 1985-05-02 1986-11-12 Societe Industrielle De Liaisons Electriques - Silec Capteur microphonique de contact à membrane piézo polymère

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2334174A (en) * 1998-02-06 1999-08-11 Rajiv Maraj Electronic stethoscope

Also Published As

Publication number Publication date
SE8900759L (sv) 1990-09-07
EP0390758A3 (fr) 1991-11-13
SE8900759D0 (sv) 1989-03-06
SE466377B (sv) 1992-02-03

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