EP1619926A1 - System und Verfahren zur Rauschunterdrückung in induktiven Empfängern - Google Patents

System und Verfahren zur Rauschunterdrückung in induktiven Empfängern Download PDF

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Publication number
EP1619926A1
EP1619926A1 EP04103484A EP04103484A EP1619926A1 EP 1619926 A1 EP1619926 A1 EP 1619926A1 EP 04103484 A EP04103484 A EP 04103484A EP 04103484 A EP04103484 A EP 04103484A EP 1619926 A1 EP1619926 A1 EP 1619926A1
Authority
EP
European Patent Office
Prior art keywords
noise
signal
receiver coil
noise signals
sound artifacts
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.)
Ceased
Application number
EP04103484A
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English (en)
French (fr)
Inventor
Louis Gerber
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.)
Sonova Holding AG
Original Assignee
Phonak AG
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 Phonak AG filed Critical Phonak AG
Priority to EP04103484A priority Critical patent/EP1619926A1/de
Publication of EP1619926A1 publication Critical patent/EP1619926A1/de
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L21/00—Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
    • G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
    • G10L21/0208—Noise filtering
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R25/00—Electric hearing aids
    • H04R25/55—Electric hearing aids using an external connection, either wireless or wired
    • H04R25/558—Remote control, e.g. of amplification, frequency
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L21/00—Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
    • G10L21/06—Transformation of speech into a non-audible representation, e.g. speech visualisation or speech processing for tactile aids
    • G10L2021/065—Aids for the handicapped in understanding

Definitions

  • This invention belongs to the field of electromagnetic wave transmission and is in particular related to the wireless transmission of audible information by inductive devices.
  • Wireless communication receivers of audible information have already been known.
  • One well-known device is a wireless miniature communication receiver called "Phonito®", developed and distributed by the Applicant.
  • Such receivers are inductively coupled wireless earphones. Users who do not want to have a wire or an acoustic tube going to the ear, or users where such a wire or tube cannot be tolerated, can attach an inductive loop that may be worn around the neck under a garment such as jacket or uniform, or the inductive loop or coil can be integrated into the clothing. The inductive loop sends the information to be heard that has been transformed into the appropriate inductive transmission form, to the earphone where it is received and re-transformed into acoustic waves.
  • the receiver worn in connection with the inductive loop and which provides speech information may be a mobile radio such as e.g. a portable citizen's band (CB) receiver, a portable telephone or any other information source that is capable of receiving wireless or broadcast information.
  • CB portable citizen's band
  • miniaturized ITE (in-the-ear) devices and/or BTE (behind-the-ear) devices considered in this document are being used since several years in the field of security and police, in acoustic studios, for sport applications, and in any other field where the presence of an acoustic communication should be kept discreet or secret. These devices are working based on the principle of inductive signal transmission and reception.
  • An audio signal U(t) that is generated at the output of a sound device such as a mobile radio receiver, a portable or fixed telephone, etc., is transmitted via an appropriate amplifier into a closed wire loop or an inductive coil.
  • a coil it will preferably be miniaturized.
  • This loop or coil that is typically worn by the user will generate a magnetic field whose field intensity H(t) is correlated to the original signal U(t). In most cases, this correlation is a proportional one or a simple mathematical function of the original signal.
  • inductive transmissions that are digital or frequency modulated.
  • interference sources are low frequency devices such as aerial conduct lines of electric trains, tramways and trolley buses; low voltage transformers for lighting purposes and their connecting and power lines that typically carry high amperages; computer monitors; inductive security systems such as tags, theft warning installations, security warn systems in casinos, banks, postal offices, etc.; electronic systems in automotive vehicles; and mobile telephones which produce the so-called 300 Hz noise. All these low frequency noise generators directly interfere with the reception field of the inductor. The consequence of this interference is a hum or still another noise that has a detrimental effect on the integrity of the signal and thus on the quality of the displayed audio signal.
  • the squelch function avoids the reception and generation of audible disturbances when no voice signal is transmitted, i.e. in speaking pauses.
  • the invention aims at providing a new and useful solution to the problem of low frequency disturbances, interference and noise in inductive transmission systems of the kind described above.
  • the invention therefore concerns a method for noise suppression in inductive receivers.
  • the present invention also relates to a system for carrying out the method.
  • an inductive receiver comprises a receiver coil, wherein audio information is transmitted from a transmitter coil or loop in a wireless manner to said receiver coil, wherein the signal received by said receiver coil is analyzed by digital signal processing in the hearing frequency range and/or the speaking time range for discrete noise signals and other sound artifacts, and said noise signals and other sound artifacts are removed from said signal.
  • a DSP (Digital Signal Processing) module can e.g. manipulate analog information, such as e.g. sound that has been converted into a digital form.
  • DSP can e.g. also comprise the use of a data compression technique.
  • a DSP element can comprise a digital signal processor, i.e. a specialized type of processor designed for performing the mathematics involved in DSP.
  • the DSPs can be programmable, which means that they can be used for manipulating different types of information, including e.g. sound, images, and video.
  • Said noise can e.g. be a low frequency noise in the range of from 50Hz to 4-8 kHz.
  • An audio signal is restored after the removal of said noise signals and other sound artifacts.
  • the analysis of the received signal and/or the restoration of said signal and/or the removal of said noise signals and other sound artifacts can be accomplished by the use of at least one algorithm of acoustic speech processing.
  • Said at least one algorithm of acoustic speech processing can be selected from algorithms based on the principles of speech theory.
  • Said algorithm can e.g. comprise a Wiener filtering method.
  • the method of the invention uses algorithms to implement the restoration of the original speech signals by analyzing the spectrum and the dynamics of the received, noisy or disturbed signal according to principles based on the theory of speech.
  • Audio Noise Reduction examples include: (1) noise reduction by spectral weighting, (2) noise reduction using coherent properties, (3) noise cancellation using Wiener filtering in the frequency domain, (4) directive beam forming, and still others.
  • spectral regions of the mixed signal of speech and noise are attenuated with different factors.
  • the spectral weighting is usually performed in a transformation domain; a common transformation is the Fourier transformation which provides an equidistant frequency resolution.
  • a common transformation is the Fourier transformation which provides an equidistant frequency resolution.
  • acoustic noise is reduced by a Generalized Sidelobe Canceller (GSC) that reasonably suppresses the coherent noise components while a Wiener filter (see below) is designed to suppress the spatial incoherent noise components.
  • GSC Generalized Sidelobe Canceller
  • Wiener filter see below
  • the Wiener filtering method is based on minimizing the mean square error between the speech S(f) and the estimate Y(f) where the fact may be used that speech and noise are statistically not correlated.
  • Method (4) refers to speech recognition and/or extraction form noise and uses a microphone array of which the different microphones can e.g. detect the phase difference and/or time of flight (tof) of the incoming signal.
  • the beamforming can e.g. seek to exploit the phase differences between microphone signals before combining the outputs of the microphones to restore the original speech.
  • the method of the invention may be implemented in using electronic components already known per se.
  • the received signal is digitized in an A/D converter, is analyzed e.g. by algorithms being adapted to speech patterns and/or by comparison with stored speech patterns, discrete noise signals and clearly distinguishable artifacts are filtered out using at least one stored algorithm, and the purified digital signal is sent to the earphone or earplug. If necessary or required, the digital output can be re-transformed to analog signals.
  • the method and the corresponding system are designed for preferably removing low frequency noise, in particular between 50Hz and 4-8 kHz, taking into consideration that a great deal of disturbing and interfering noise originates from this frequency range.
  • This noise can be e.g. in the form of sinusoidal signals or set of harmonics that may also be amplitude modulated.
  • As example can serve the 900 MHz GSM (Global System for Mobile Communications) radio frequency signal which is switched at a rate of 300Hz.
  • GSM Global System for Mobile Communications
  • the invention allows to drastically improve the quality of wireless speech and voice transmission by induction. Furthermore, additional application fields are opened to inductive speech transmission. It is even conceivable to transmit also, additionally or alternatively, sound and music with an improved quality.

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  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Physics & Mathematics (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Human Computer Interaction (AREA)
  • Audiology, Speech & Language Pathology (AREA)
  • Quality & Reliability (AREA)
  • Computational Linguistics (AREA)
  • Multimedia (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Health & Medical Sciences (AREA)
  • Neurosurgery (AREA)
  • Otolaryngology (AREA)
  • Noise Elimination (AREA)
EP04103484A 2004-07-21 2004-07-21 System und Verfahren zur Rauschunterdrückung in induktiven Empfängern Ceased EP1619926A1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP04103484A EP1619926A1 (de) 2004-07-21 2004-07-21 System und Verfahren zur Rauschunterdrückung in induktiven Empfängern

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP04103484A EP1619926A1 (de) 2004-07-21 2004-07-21 System und Verfahren zur Rauschunterdrückung in induktiven Empfängern

Publications (1)

Publication Number Publication Date
EP1619926A1 true EP1619926A1 (de) 2006-01-25

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Family Applications (1)

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EP04103484A Ceased EP1619926A1 (de) 2004-07-21 2004-07-21 System und Verfahren zur Rauschunterdrückung in induktiven Empfängern

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EP (1) EP1619926A1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1819195A2 (de) 2006-02-13 2007-08-15 Phonak Communications Ag Verfahren und System zur Hörhilfebereitstellung für einen Benutzer
US7738666B2 (en) 2006-06-01 2010-06-15 Phonak Ag Method for adjusting a system for providing hearing assistance to a user

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5734976A (en) * 1994-03-07 1998-03-31 Phonak Communications Ag Micro-receiver for receiving a high frequency frequency-modulated or phase-modulated signal
CA2406754A1 (en) * 1998-04-16 1998-10-22 Dspfactory Ltd. Method and apparatus for noise reduction, particularly in hearing aids
WO2003015382A1 (en) * 2001-08-07 2003-02-20 James Edward Aman Mobile phone and hands-free kit with inductive link

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5734976A (en) * 1994-03-07 1998-03-31 Phonak Communications Ag Micro-receiver for receiving a high frequency frequency-modulated or phase-modulated signal
CA2406754A1 (en) * 1998-04-16 1998-10-22 Dspfactory Ltd. Method and apparatus for noise reduction, particularly in hearing aids
WO2003015382A1 (en) * 2001-08-07 2003-02-20 James Edward Aman Mobile phone and hands-free kit with inductive link

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1819195A2 (de) 2006-02-13 2007-08-15 Phonak Communications Ag Verfahren und System zur Hörhilfebereitstellung für einen Benutzer
US7738665B2 (en) 2006-02-13 2010-06-15 Phonak Communications Ag Method and system for providing hearing assistance to a user
US7738666B2 (en) 2006-06-01 2010-06-15 Phonak Ag Method for adjusting a system for providing hearing assistance to a user

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