EP0280907A1 - Montage pour la suppression d'oscillations - Google Patents

Montage pour la suppression d'oscillations Download PDF

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Publication number
EP0280907A1
EP0280907A1 EP88101630A EP88101630A EP0280907A1 EP 0280907 A1 EP0280907 A1 EP 0280907A1 EP 88101630 A EP88101630 A EP 88101630A EP 88101630 A EP88101630 A EP 88101630A EP 0280907 A1 EP0280907 A1 EP 0280907A1
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EP
European Patent Office
Prior art keywords
circuit
frequency
arrangement according
signals
influencing
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.)
Granted
Application number
EP88101630A
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German (de)
English (en)
Other versions
EP0280907B1 (fr
Inventor
Jürgen Dipl.-Ing. Wagner (FH)
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.)
Sivantos GmbH
Original Assignee
Siemens AG
Siemens Audiologische Technik GmbH
Siemens Corp
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.)
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Publication date
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Application filed by Siemens AG, Siemens Audiologische Technik GmbH, Siemens Corp filed Critical Siemens AG
Priority to AT88101630T priority Critical patent/ATE68310T1/de
Publication of EP0280907A1 publication Critical patent/EP0280907A1/fr
Application granted granted Critical
Publication of EP0280907B1 publication Critical patent/EP0280907B1/fr
Anticipated expiration legal-status Critical
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    • 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
    • H04R25/45—Prevention of acoustic reaction, i.e. acoustic oscillatory feedback
    • H04R25/453—Prevention of acoustic reaction, i.e. acoustic oscillatory feedback electronically
    • 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
    • H04R25/50—Customised settings for obtaining desired overall acoustical characteristics
    • H04R25/505—Customised settings for obtaining desired overall acoustical characteristics using digital signal processing

Definitions

  • the present invention relates to a circuit arrangement according to the preamble of patent claim 1.
  • Circuits have recently been developed (for example from RIM-Elektronik, Kunststoff, or the circuits of US Pat. No. 4,232,192 and US Pat. No. 4,079,199) which recognize vibrations as such and then suppress them.
  • Such circuits tap the useful signal between the input converter and a power amplifier connected upstream of the output converter and amplify it by means of an additional amplifier.
  • the amplified signal is compared in a comparator stage with a threshold voltage and fed into a phase locked loop (so-called phase locked loop or PLL for short).
  • the PLL recognizes one Vibration, if it occurs, and provides a suppression signal to a notch filter upstream of the power amplifier that suppresses the frequency range of the vibration (or, in the case of U.S. Patent No. 4,079,199, the gain is reduced).
  • a PLL becomes unstable when the input signal disappears. It drifts. The result of the drift is a periodic acoustic interference signal.
  • the object of the present invention is to construct a vibration suppression circuit which, when a vibration occurs in the useful signal, suppresses this vibration and remains stable (does not begin to drift) when the input signal disappears.
  • the PLL in the circuit arrangement is replaced by an oscillation frequency search circuit which comprises a frequency detection device for the frequency found, which continues to emit a signal even when the oscillation disappears, which keeps the influencing circuit (e.g. notch filter) in a fixed state.
  • the influencing circuit e.g. notch filter
  • a preferred embodiment of the invention results from the dependent claim 2.
  • the circuit between the power amplifier and output converter switched on, which makes it possible to dispense with the additional amplifier used in the prior art.
  • the circuit arrangement can be made cheaper and, particularly in the case of hearing aids, more space-saving.
  • Fig. 1 shows a circuit arrangement according to the invention, which can be installed, for example, in a hearing aid. It comprises a microphone 1 as an acoustic input converter, which converts acoustic input signals into electrical signals SO, an acoustic output converter 2 (which is designed either as a loudspeaker or, especially in hearing aids, as a so-called receiver), a power amplifier 3 connected upstream of the output converter 2 and one Vibration suppression circuit 4 designed according to the invention.
  • a microphone 1 as an acoustic input converter, which converts acoustic input signals into electrical signals SO
  • an acoustic output converter 2 which is designed either as a loudspeaker or, especially in hearing aids, as a so-called receiver
  • a power amplifier 3 connected upstream of the output converter 2
  • Vibration suppression circuit 4 designed according to the invention.
  • the vibration suppression circuit 4 is designed as an electrical feedback circuit. It suppresses electrical signals that are generated due to acoustic feedback effects and that usually lead to undamped vibrations in the circuit.
  • the feedback effect is indicated in FIG. 1 with a dashed arrow line between acoustic output transducer 2 and microphone 1.
  • An acoustic useful signal SE together with an acoustic feedback signal SR is converted in the microphone 1 into an electrical signal S0.
  • the output signal S5 of the vibration suppression circuit 4 is subtracted from this signal S0 in a subtractor 5 from the signal S0.
  • the remaining signal S1 is amplified in a non-inverting power amplifier 3 to a signal S2.
  • the signal S2 is converted back into an acoustic signal SA in the output converter 2.
  • the signal S2 is fed to the vibration suppression circuit 4 as an input signal.
  • the function of the vibration suppression circuit 4 consists of a vibration detection circuit 6, a vibration frequency search circuit 7 and an influencing circuit 8.
  • the input signal S2 is passed to the vibration detection circuit 6. It is also fed to the influencing circuit 8.
  • the vibration detection circuit 6 it is checked whether the signal S2 contains a vibration based on acoustic feedback effects. If an oscillation is present, an oscillation detection signal S3 is emitted.
  • the signal S3 sets the oscillation frequency search circuit 7 into operation, a sequence of signals S4 being emitted by the oscillation frequency search circuit 7 until the oscillation detection signal S3 at the output of the oscillation detection circuit 6 disappears.
  • the Vibration detection signal S3 pending signal S4 at the output of the oscillation frequency search circuit 7 is held by the search circuit 7 until a new oscillation occurs.
  • the signals S4 control the influencing circuit 8, in the sense that frequency ranges which are to be assigned to a detected oscillation are largely suppressed in the entire captured frequency spectrum of the signal SO by means of a filter.
  • the output signal S5 of the influencing circuit 8 is the output signal of the vibration suppression circuit 4.
  • the vibration detection circuit 6 checks the input signal S2 for these properties. In a first stage, the amplitude of the input signal S2 is compared with a first threshold voltage UT1 by means of a first comparator 9. If the amplitude of S2 exceeds the threshold UT1, a square wave voltage S21 is generated.
  • the following stage comprises an RC element with an ohmic resistor 10, diode 10 ⁇ and capacitor 11 and a second comparator 12.
  • the capacitor 11 is quickly charged by the signal S21 via the diode 10 and discharged again via the resistor 10 with a predetermined time constant.
  • the time constant together with the threshold voltage UT2 of the second comparator 12 determines the minimum frequency to which the vibration detection circuit 6 responds. If a small time constant is selected, then the vibration detection circuit 6 essentially only responds to high-frequency signals. In the case of low-frequency signals, the capacitor 11 has sufficient time to discharge below the threshold voltage UT2 of the second comparator 12. These low-frequency signals are therefore not detected. This ensures that the vibration detection circuit 6 only responds to signals that derive from acoustic feedback effects, while portions of the useful signal (eg voice signal) that occur periodically at a lower frequency are not taken into account.
  • the useful signal eg voice signal
  • output signals S23 are released to a third stage 13 to 16.
  • the output signals S23 are square-wave voltages which have the same duration as the threshold value violations of the signals S22.
  • the signals S23 thus reflect how long a large, high-frequency input signal lasts.
  • the third stage comprises a diode 13, an RC element 14, 15 and a third comparator 16. With the signal S23, the capacitor 15 is charged via the resistor 14. Resistor 14 and capacitor 15 are dimensioned so that the charging time constant is large, e.g. 0.5 to 2 seconds. If the output voltage S23 drops only briefly, the capacitor 15 is immediately completely discharged via the diode 13.
  • the capacitor 15 charges to such an extent that the voltage exceeds the threshold UT3 of the subsequent third comparator 16.
  • the input signal S2 fulfills all vibration detection criteria and the signal S3 output by the comparator 16 is considered to be a vibration detection signal.
  • the oscillation frequency search circuit 7 is arranged between the oscillation detection circuit 6 and the influencing circuit 8 and controls the influencing circuit 8 in such a way that detected oscillations are suppressed.
  • a first device 17 of the search circuit 7 generates digital frequency-determining signals S33 and is controlled by the vibration detection signals S3.
  • the main component of the first device 17 is a counting device 18 which a counter 19, a counting direction switch 20 and a reset element 21, also called "power-on reset".
  • the first device 17 includes an oscillator 22 and an associated AND gate 23.
  • the counter 19 also serves as a holding device for the frequencies of the detected vibration, as will be explained in more detail below.
  • the reset element 21 ensures that the output signals S32 on all four output lines of the counter 19 are in the zero state (also referred to as the “low” state).
  • This 0000 value is digitally incremented by one each time a pulse S31 ("high” state) is registered at the input of the counter 19. After all four output lines have been switched to "high”, the original zero state is restored at the next pulse S31 and the step-up sequence is repeated.
  • a pulse S31 is only generated if a vibration detection pulse S3 is present at the AND gate 22 connected upstream of the counter 19. If this is the case, then the pulses S31 ⁇ generated by the oscillator 22 are forwarded as step-up pulses S31.
  • the oscillator 22 therefore determines the speed at which the counter 19 is advanced.
  • the counter 19 continues to switch the output pulses S32 until the vibration detection signal S3 disappears. (Signal S3 disappears if the oscillation has been suppressed by the influencing circuit 8.) When the signal S3 disappears, the counter 19 receives no further pulses S31 and remains in the set state until a new oscillation detection signal S3 occurs.
  • the counter 19 thus stores the set state and therefore, together with the AND gate 23, serves as a holding device for holding the frequency of the detected vibration at the influencing circuit 8. It is advantageous to design the oscillation frequency search circuit 7 as a holding device, since the vibration suppression circuit 4 does not drift can and a return of the suppressed vibration is avoided.
  • the first device 17 also includes at the output of the counter 19 a counting direction switch 20.
  • This has the effect that a sudden change from 111 to 000 is avoided in the digital frequency-determining output signals S33, by counting down every second sequence by inversion of the input signals S32 from 111 to 000 becomes.
  • This is advantageous in that the filter arranged in the influencing circuit 8 for suppressing the oscillation frequency when the counting direction is reversed does not jump from one end to the other end of the frequency spectrum, but instead moves back and forth in the frequency spectrum.
  • a second device 24 of the oscillation frequency search circuit 7 samples the frequency-determining signals S33 of the first device 17 (output of the counting direction switch 20) and controls the influencing circuit 8 via the signals S4.
  • a decoder 25 transmits the eight signal possibilities arriving via three lines to eight different lines. These eight signals S4 control the influencing circuit 8 in the sense that they determine which frequency range in the controllable frequency spectrum is filtered by the influencing circuit 8.
  • the decoder 25 controls the influencing circuit 8 by means of a discretely variable resistor 26.
  • the influencing circuit 8 also comprises further ohmic resistors 30, capacitors 31 and an amplifier 32, which are arranged in the form of a bandpass filter.
  • a bandpass filter is e.g. known from the book "Semiconductor Circuit Technology” by Tietze and Schenk (Springer-Verlag Berlin, Heidelberg, 7th edition (1985), pages 419-421). Since the bandpass filter is designed as a negative feedback of the power amplifier 3, the circuit 8 simulates a notch filter, which forms a suction circuit at the resonance frequency. The bandwidth and gain of the filter are independent of the discretely variable resistor 26. The resonance frequency can thus be varied by changing the resistance values in the resistor 26 without influencing the bandwidth or amplification.
  • the output resistor 33 determines the weight of the feedback S5 on the subtractor 5 (see FIG. 1).
  • FIG. 5 Another possibility of influencing vibrations (modification of FIG. 4) is shown in FIG. 5.
  • a CR high-pass filter is used in the influencing circuit 8 'instead of a band-pass filter.
  • this filter simulates a variable capacitor that enables smoothing of the acoustic reproduction curve and has a low-pass effect.
  • the above-described vibration detection circuit 6 and vibration frequency search circuit 7 can be used unchanged in this embodiment.
  • the circuit 8 ⁇ could be designed as a phase shifter, phase switch or gain reducer.
  • Figure 6 shows e.g. a variant of the oscillation detection circuit 6 and the oscillation frequency search circuit 7.
  • the third comparator stage 13 to 16 of the oscillation detection circuit 6 ' is replaced by a counter stage which comprises an inverter 36, a digital counter 37 and an AND gate 38.
  • the input signal is checked in the same way as in the exemplary embodiment corresponding to FIG. 2 according to the vibration characteristics "large amplitude" and "high frequencies". However, an output signal S23 is digitally processed to determine whether the large, high-frequency input signal is long-lasting.
  • Counter 37 has two signal inputs: an input for the square wave voltage S21 and a reset input which, together with the inverter 36, constantly resets the counter 37 to the zero state, except when a signal S23 occurs. As long as a signal S23 is present, the counter 37 counts the square-wave signals S21. After a certain number of signals S21 has occurred, the input signal is regarded as a recognized vibration. The counter 37 then generates step pulses S3 together with the AND gate 38. These advance pulses can be given directly to the counter 19 of the search circuit 7 '. This circuit variant therefore does not require an oscillator.

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  • Acoustics & Sound (AREA)
  • General Health & Medical Sciences (AREA)
  • Neurosurgery (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Signal Processing (AREA)
  • Stereo-Broadcasting Methods (AREA)
  • Coating With Molten Metal (AREA)
  • Gyroscopes (AREA)
  • Amplifiers (AREA)
  • Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
EP88101630A 1987-02-17 1988-02-04 Montage pour la suppression d'oscillations Expired - Lifetime EP0280907B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT88101630T ATE68310T1 (de) 1987-02-17 1988-02-04 Schaltungsanordnung zum unterdruecken von schwingungen.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3704999 1987-02-17
DE3704999 1987-02-17

Publications (2)

Publication Number Publication Date
EP0280907A1 true EP0280907A1 (fr) 1988-09-07
EP0280907B1 EP0280907B1 (fr) 1991-10-09

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ID=6321173

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EP88101630A Expired - Lifetime EP0280907B1 (fr) 1987-02-17 1988-02-04 Montage pour la suppression d'oscillations

Country Status (5)

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US (1) US4815140A (fr)
EP (1) EP0280907B1 (fr)
AT (1) ATE68310T1 (fr)
DE (1) DE3865319D1 (fr)
DK (1) DK77888A (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0600164A1 (fr) * 1992-09-08 1994-06-08 Alcatel SEL Aktiengesellschaft Procédé pour l'amélioration de la qualité de transmission d'un dispositif électro-acoustique

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4985925A (en) * 1988-06-24 1991-01-15 Sensor Electronics, Inc. Active noise reduction system
US5091952A (en) * 1988-11-10 1992-02-25 Wisconsin Alumni Research Foundation Feedback suppression in digital signal processing hearing aids
US6563931B1 (en) 1992-07-29 2003-05-13 K/S Himpp Auditory prosthesis for adaptively filtering selected auditory component by user activation and method for doing same
US5412734A (en) * 1993-09-13 1995-05-02 Thomasson; Samuel L. Apparatus and method for reducing acoustic feedback
US6137888A (en) * 1997-06-02 2000-10-24 Nortel Networks Corporation EM interference canceller in an audio amplifier
AU2004201374B2 (en) * 2004-04-01 2010-12-23 Phonak Ag Audio amplification apparatus
AU2003236382B2 (en) * 2003-08-20 2011-02-24 Phonak Ag Feedback suppression in sound signal processing using frequency transposition
US7756276B2 (en) * 2003-08-20 2010-07-13 Phonak Ag Audio amplification apparatus
EP2053876B1 (fr) * 2007-10-18 2010-05-26 Siemens Medical Instruments Pte. Ltd. Dispositif auditif doté d'un raccordement commun pour le blindage et l'identification d'un récepteur

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4079199A (en) * 1977-05-25 1978-03-14 Patronis Jr Eugene T Acoustic feedback detector and automatic gain control
US4091236A (en) * 1976-09-07 1978-05-23 The University Of Akron Automatically tunable notch filter and method for suppression of acoustical feedback
US4232192A (en) * 1978-05-01 1980-11-04 Starkey Labs, Inc. Moving-average notch filter

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL7612358A (nl) * 1976-11-08 1978-05-10 Philips Nv Versterkerinrichting voor akoestische signalen voorzien van middelen voor het onderdrukken van ongewenste stoorsignalen.

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4091236A (en) * 1976-09-07 1978-05-23 The University Of Akron Automatically tunable notch filter and method for suppression of acoustical feedback
US4079199A (en) * 1977-05-25 1978-03-14 Patronis Jr Eugene T Acoustic feedback detector and automatic gain control
US4232192A (en) * 1978-05-01 1980-11-04 Starkey Labs, Inc. Moving-average notch filter

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
HEARING INSTRUMENTS, Band 37, Nr. 4, April 1986, Seiten 34,36,41,51, Cleveland, Ohio, US; D.A. PREVES et al.: "A feedback stabilizing circuit for hearing aids" *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0600164A1 (fr) * 1992-09-08 1994-06-08 Alcatel SEL Aktiengesellschaft Procédé pour l'amélioration de la qualité de transmission d'un dispositif électro-acoustique

Also Published As

Publication number Publication date
EP0280907B1 (fr) 1991-10-09
US4815140A (en) 1989-03-21
DE3865319D1 (de) 1991-11-14
DK77888D0 (da) 1988-02-16
ATE68310T1 (de) 1991-10-15
DK77888A (da) 1988-08-18

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