EP0485357A2 - Hearing aid with filter circuit - Google Patents

Hearing aid with filter circuit Download PDF

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Publication number
EP0485357A2
EP0485357A2 EP91890266A EP91890266A EP0485357A2 EP 0485357 A2 EP0485357 A2 EP 0485357A2 EP 91890266 A EP91890266 A EP 91890266A EP 91890266 A EP91890266 A EP 91890266A EP 0485357 A2 EP0485357 A2 EP 0485357A2
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EP
European Patent Office
Prior art keywords
filter
amplifier
hearing aid
feedback loop
frequency response
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Granted
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EP91890266A
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German (de)
French (fr)
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EP0485357A3 (en
EP0485357B1 (en
Inventor
Zlatan Dipl.-Ing. Dr. Ribic
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Viennatone AG
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Viennatone AG
Viennatone GmbH
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R25/00—Deaf-aid sets, i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception
    • H04R25/50—Customised settings for obtaining desired overall acoustical characteristics
    • H04R25/502—Customised settings for obtaining desired overall acoustical characteristics using analog signal processing

Definitions

  • the invention relates to a hearing aid with a microphone, at least one amplifier acted upon by its signal, which interacts to influence the frequency response with a higher-order filter, which is designed as a multiple filter, and a loudspeaker, which converts the amplified signals into sound waves.
  • bandpass filters which influence the frequency response more or less.
  • bandpass filters which are formed from a high and a low pass filter, a case is known where a "graphic equalizer" is used, a parallel connection of several bandpass filters with fixed frequency bands, but independently controllable amplitudes.
  • filters of a higher order which enable a correspondingly good adaptation of the frequency response, require a relatively high expenditure on components.
  • the aim of the invention is to propose a hearing aid of the type mentioned at the beginning, in which an optimal adaptation of the frequency response is possible.
  • the filter has a biquadratic structure and has at least two integrators and an inverting amplifier, in which components the active elements are formed by discrete components, in particular individual transistors.
  • This measure has the advantage that two or three parameters can be controlled in a simple manner.
  • the filter is arranged in the feedback loop of the amplifier.
  • the individual stages of the filter are connected to one another by one or more feedback lines.
  • This measure allows a particularly good adaptation of the hearing aid frequency response to be achieved by installing adjustable components in the feedback lines.
  • the feedback loop of the amplifier is guided via a potentiometer for setting the filter increase or decrease and a potentiometer for setting the center frequency of the filter is arranged in the filter circuit.
  • Fig. 1 shows a block diagram of a hearing aid according to the invention, wherein the microphone 1 converts the sound signal into an electrical signal, which is amplified in the preamplifier 2, then passes through the filter 3 to influence the frequency response and finally after it in the power amplifier 4 the required output level has been amplified, is converted back into an acoustic sound signal by a loudspeaker 5.
  • the filter is arranged in a conventional manner between two amplifier stages.
  • FIG. 2 shows a block diagram of a hearing device according to the invention, the filter being arranged in the feedback loop of an amplifier.
  • the microphone 1 converts the sound signal into an electrical signal, which is amplified in the preamplifier 2. Then it passes through the intermediate amplifier 6, in the feedback loop of which the filter 3 is arranged, as a result of which the signal is influenced in a frequency-selective manner. Then the signal in the power amplifier 4 is amplified to the required output level and finally converted again by the loudspeaker 5 into an acoustic sound signal.
  • Fig. 3 shows the basic structure of such a filter 3.
  • This has a biquadratic structure, the transistors T2 and T3 in conjunction with the resistor R F1 and the capacitor C1, or the resistor R F2 and the capacitor C2 form two integrators .
  • the phase inversion stage required for a biquadratic structure is formed by the transistor T1 and the associated resistors R I2 , R X R A1 .
  • the load resistances of the transistors T1 to T3 are denoted by R A1 , R A2 and R A3 .
  • transistor T3 is fed back to the base of transistor T1 via resistor R x .
  • the base of transistor T1 is used as an input, the collector outputs of all three transistors T1, T2 and T3 being available as outputs.
  • the collector of transistor T1 gives a high-pass output (FIG. 4a)
  • the collector of transistor T2 gives a band-pass output (FIG. 4b)
  • the collector of transistor T3 gives a low-pass output (FIG. 4c).
  • the same filter can thus be provided for different applications.
  • the center frequency of this filter is determined by the resistors R F1 and / or R F2 and the capacitors C1 and C2.
  • the filter 3 shown in FIG. 3 is a simplified Kerwin-Huelsman-Newcomb structure which is used for Group of biquadratic filters counts.
  • all three basic connections can be connected to a common input using three high-resistance resistors.
  • the collectors of transistors T1 or T3 can be used as a bandpass output. But then there is no high-pass exit.
  • Such a circuit then corresponds to a Tow-Thomas structure, which is also one of the biquadratic filters.
  • the base of transistor T3 can be used alone as an input.
  • the transistor T4 with its load resistor R5 serves as an amplifier, a base-collector negative feedback via the resistors R2 and R3 being provided in a known manner for operating point stabilization and gain adjustment.
  • this amplifier 6 is connected to the filter 3, which lies in the feedback loop of the amplifier 6.
  • the transistors T1 to T3 form a biquadratic structure, the transistor T3 with the resistor R I2 and the capacitor C1 as well as the transistor T2 with the capacitor top C2 and the resistor R I1 forming the two integrators.
  • the phase inversion stage is formed by the transistor T1 with the resistors R F and R7.
  • the gain of this amplifier T1 arranged in the filter 3 can be changed by the resistor R F connected as a potentiometer, the change in the gain also shifting the resonance frequency of the entire filter 3 results.
  • the working resistances of the filter 3 are formed by the resistors R8, R9 and R10.
  • the collector of the transistor T3 represents the bandpass output of the filter 3, a signal in phase opposition to it being able to be tapped at the collector of the transistor T1.
  • the amplitude and the phase of the signal fed back to the amplifier 6 can be influenced by the potentiometer R A.
  • the feedback of the transistor T4 can be selected such that, depending on the setting of the potentiometer R A , a positive increase (positive feedback) selective increase or a negative feedback (negative feedback) a reduction of the signal passing through the filter 3 is achieved.
  • the quality of the filter 3 is essentially determined by the dimensioning of the resistors R2, R3 and R4.
  • FIG. 6 shows, for example, the function of the circuit according to FIG. 5, the center frequencies of the increases or decreases being able to be selected by adjusting the resistance R F.
  • FIG. 6 shows only a few frequency responses which are picked out arbitrarily, the course of the curves above and below the center line indicating the extent to which the increase or decrease can be varied at the individual frequencies.

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  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Neurosurgery (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Networks Using Active Elements (AREA)
  • Tone Control, Compression And Expansion, Limiting Amplitude (AREA)
  • Amplifiers (AREA)

Abstract

Hearing aid with a microphone, at least one amplifier supplied with signals from the latter, which amplifier interacts with a higher-order filter in order to influence the frequency response, and a loudspeaker which converts the amplified signals into sound waves. This filter (3) can be disposed in conventional fashion between two amplifier stages or in the feedback loop of the amplifier (6). To enable optimum adaptation of the frequency response to the respective requirements in a hearing aid of this type, it is provided that the filter (3) is designed as a multiple filter with a biquadratic structure and has at least two integrators and an inverting amplifier, in which components the active elements are formed by transistors, preferably individual transistors (T1, T2, T3). The feedback loop of the amplifier (6) is led via an adjustable potentiometer (RA) for adjustment of the filter emphasis or de-emphasis and an adjustable potentiometer (RF) is disposed in the filter circuit (3) for adjustment of the mid-frequency of the filter (3). <IMAGE>

Description

Die Erfindung bezieht sich auf ein Hörgerät mit einem Mikrofon, mindestens einem von dessen Signal beaufschlagten Verstärker, der zur Beeinflussung des Frequenzganges mit einem Filter höherer Ordnung, das als Mehrfachfilter ausgebildet ist, zusammenwirkt und einem Lautsprecher, der die verstärkten Signale in Schallwellen umwandelt.The invention relates to a hearing aid with a microphone, at least one amplifier acted upon by its signal, which interacts to influence the frequency response with a higher-order filter, which is designed as a multiple filter, and a loudspeaker, which converts the amplified signals into sound waves.

Für die Anpassung eines Hörgerätes an die jeweiligen Erfordernisse des Trägers ist es notwendig, den Frequenzgang des Gerätes entsprechend zu wählen und einzustellen. Zu diesem Zweck ist es bekannt, Hoch- und/oder Tiefpaßfilter zu verwenden, welche den Frequenzgang mehr oder weniger beeinflussen. Manchmal werden auch Bandpaßfilter verwendet, die aus jeweils einem Hoch- und einem Tiefpaßfilter gebildet sind ist ein Fall bekannt, wo ein "Graphic Equalizer" zur Anwendung kommt, eine Parallelschaltung von mehreren Bandpaßfiltern mit festgelegten Frequenzbändern, aber unabhängig regelbaren Amplituden. Allerdings erfordern Filter höherer Ordnung, die eine entsprechend gute Anpassung des Frequenzganges ermöglichen, einen relativ hohen Aufwand an Bauteilen.To adapt a hearing aid to the respective requirements of the wearer, it is necessary to select and adjust the frequency response of the device accordingly. For this purpose, it is known to use high and / or low pass filters which influence the frequency response more or less. Sometimes bandpass filters are used, which are formed from a high and a low pass filter, a case is known where a "graphic equalizer" is used, a parallel connection of several bandpass filters with fixed frequency bands, but independently controllable amplitudes. However, filters of a higher order, which enable a correspondingly good adaptation of the frequency response, require a relatively high expenditure on components.

Wie zahlreiche Untersuchungen ergaben, genügt es zur Erzielung der meisten in der Praxis angestrebten Frequenzgang-Kurven, eines der bekannten Hoch- und/oder Tiefpaßfilter mit einem Bandequalizer zu kombinieren, der es ermöglicht, ein relativ schmales Frequenzband mit beliebig wählbarer Mittenfrequenz anzuheben oder abzusenken. Für einen solchen Bandequalizer bietet sich ein parametrisches Filter an, wie es - mit Operationsverstärkern aufgebaut - in der Studiotechnik seit langem in Verwendung steht. Ein solches parametrisches Filter erfordert aber einen hohen Schaltungsaufwand und war deshalb in der bislang üblichen Bauform aufgrund des geringen Platzangebotes und der niedrigen Betriebsspannung in der Hörgerätetechnik nicht verwendbar.As numerous studies have shown, it is sufficient to achieve most of the frequency response curves sought in practice by combining one of the known high and / or low pass filters with a band equalizer, which makes it possible to raise or lower a relatively narrow frequency band with an arbitrarily selectable center frequency. For such a band equalizer, there is a parametric filter that has been used in studio technology for a long time - built with operational amplifiers. However, such a parametric filter requires a high level of circuitry and was therefore not usable in the hearing aid technology in the previously customary design due to the limited space available and the low operating voltage.

Ziel der Erfindung ist es ein Hörgerät der eingangs erwähnten Art vorzuschlagen, bei dem eine optimale Anpassung des Frequenzganges möglich ist.The aim of the invention is to propose a hearing aid of the type mentioned at the beginning, in which an optimal adaptation of the frequency response is possible.

Erfindungsgemäß wird dies dadurch erreicht, daß das Filter eine biquadratische Struktur aufweist und mindestens zwei Integratoren und einen invertierenden Verstärker, bei welchen Bauteilen die aktiven Elemente durch diskrete Bauteile, insbesondere Einzel-Transistoren, gebildet sind, aufweist.This is achieved according to the invention in that the filter has a biquadratic structure and has at least two integrators and an inverting amplifier, in which components the active elements are formed by discrete components, in particular individual transistors.

Durch diese Maßnahme ergibt sich der Vorteil, daß sich zwei bzw. drei Parameter auf einfache Weise regeln lassen. So können z.B. die Mittenfrequenz, die Filtergüte bzw. die Amplitude der Anhebung bzw. der Absenkung, als auch die Filterart, z.B. Tiefpaß, Hochpaß oder Bandpaß, je nach Anordnung des Filterausganges gewählt werden.This measure has the advantage that two or three parameters can be controlled in a simple manner. For example, the center frequency, the filter quality or the amplitude of the increase or decrease, as well as the type of filter, e.g. Low pass, high pass or band pass, depending on the arrangement of the filter output.

Mehrfachfilter mit biquadratischer Struktur sind in der Literatur bekannt, z.B. aus "RC Active Filter design hand-book", J. Wiley & Sons, 1985, doch sind diese Filter stets mit Operationsverstärkern aufgebaut. Ein solcher Aufbau des Filters ist aber für Hörgeräteanwendungen nicht geeignet, da es aufgrund des geringen zur Verfügung stehenden Raumes nicht möglich ist, zusätzlich zu den üblichen Verstärker-Bauteilen, die für das Filter notwendigen Bauteile und die bisher erforderlichen drei Operationsverstärker unterzubringen. Außerdem reicht auch die in der Regel für Hörgeräte vorgesehene Spannungsversorgung mit einer 1,4V-Batterie, durchschnittliche Betriebsspannung 1,2 - 1,3V, für den Betrieb von Operationsverstärkern nicht aus. Eine Spannungsquelle mit höherer Spannung läßt sich aber aus Platzgründen in einem Hörgerät (Ausnahme: Kästchengerät) nicht unterbringen.Multiple filters with a biquadratic structure are known in the literature, e.g. from "RC Active Filter design hand-book", J. Wiley & Sons, 1985, but these filters are always built with operational amplifiers. Such a construction of the filter is, however, not suitable for hearing aid applications since, due to the limited space available, it is not possible to accommodate the components required for the filter and the three operational amplifiers previously required in addition to the usual amplifier components. In addition, the voltage supply with a 1.4V battery, average operating voltage 1.2-1.3V, which is usually provided for hearing aids, is not sufficient for the operation of operational amplifiers. However, a voltage source with a higher voltage cannot be accommodated in a hearing device (exception: box device) for reasons of space.

Durch die vorgeschlagene Lösung werden diese Probleme vermieden, wobei sich trotz der Verwendung von Einzeltransistoren oder niedrig integrierter Bauteile eine Art Biquad-Filter ergibt, mit dem sich, wie bereits oben dargelegt, mehrere Parameter auf einfache Weise einstellen lassen und damit der Frequenzgang des Hörgerätes sehr weitgehend an den gewünschten Frequenzgang angepaßt werden kann.The proposed solution avoids these problems, and despite the use of individual transistors or low-integrated components, a type of biquad filter results, with which, as already explained above, several parameters can be set in a simple manner and thus the frequency response of the hearing aid is very great can be largely adapted to the desired frequency response.

Weiters kann bei einem Hörgerät mit einem mit einer Rückkopplungsschleife versehenen Verstärker vorgesehen sein, daß das Filter in der Rückkopplungsschleife des Verstärkers angeordnet ist.Furthermore, in the case of a hearing aid with an amplifier provided with a feedback loop, it can be provided that the filter is arranged in the feedback loop of the amplifier.

Auf diese Weise ist es möglich nur einen Frequenzbereich selektiv zu beeinflussen und eine Equalizerschaltung für ein Hörgegrät aufzubauen.In this way it is possible to selectively influence only one frequency range and to set up an equalizer circuit for a hearing aid.

Nach einem weiteren Merkmal der Erfindung kann vorgesehen sein, daß die einzelnen Stufen des Filters durch eine oder mehrere Rückkopplungsleitungen miteinander verbunden sind.According to a further feature of the invention, it can be provided that the individual stages of the filter are connected to one another by one or more feedback lines.

Durch diese Maßnahme läßt sich durch Einbau von einstellbaren Bauteilen in die Rückkopplungsleitungen eine besonders gute Anpassung des Hörgeräte-Frequenzganges erreichen.This measure allows a particularly good adaptation of the hearing aid frequency response to be achieved by installing adjustable components in the feedback lines.

Weiters kann vorgesehen sein, daß die Rückkopplungsschleife des Verstärkers über ein Potentiometer zur Einstellung der Filteranhebung oder -absenkung geführt ist und im Filterkreis ein Potentiometer zur Einstellung der Mittenfrequenz des Filters angeordnet ist.Furthermore, it can be provided that the feedback loop of the amplifier is guided via a potentiometer for setting the filter increase or decrease and a potentiometer for setting the center frequency of the filter is arranged in the filter circuit.

Auf diese Weise ergibt sich ein einfacher Aufbau, der aber eine sehr weitgehende Anpassung des Hörgerätes an die jeweils gewünschte Frequenzgang-Kurve ermöglicht.This results in a simple structure, which, however, enables the hearing aid to be adapted to the desired frequency response curve to a very large extent.

Die Erfindung wird nun anhand der Zeichnungen näher erläutert. Dabei zeigen:

  • Fig. 1 ein Blockschaltbild eines erfindungsgemäßen Hörgerätes, wobei das Filter zwischen zwei Verstärkerstufen angeordnet ist,
  • Fig. 2 ein Blockschaltbild eines erfindungsgemäßen Hörgerätes, wobei das Filter in der Rückkopplungsschleife eines Verstärkers angeordnet ist,
  • Fig. 3 ein erfindungsgemäßes Filter,
  • Fig. 4 (a, b und c) die Filtercharakteristika der drei, bei einem erfindungsgemäßen Filter zur Verfügung stehenden Ausgänge,
  • Fig. 5 eine praktisch ausgeführte Filterschaltung und
  • Fig. 6 die Funktion der Schaltung von Fig. 5 in einer Frequenzgangdarstellung.
The invention will now be explained in more detail with reference to the drawings. Show:
  • 1 is a block diagram of a hearing aid according to the invention, the filter being arranged between two amplifier stages,
  • 2 shows a block diagram of a hearing aid according to the invention, the filter being arranged in the feedback loop of an amplifier,
  • 3 an inventive filter,
  • 4 (a, b and c) the filter characteristics of the three outputs available in a filter according to the invention,
  • Fig. 5 is a practical filter circuit and
  • Fig. 6 shows the function of the circuit of Fig. 5 in a frequency response diagram.

Fig. 1 zeigt ein Blockschaltbild eines erfindungsgemäßen Hörgerätes, wobei das Mikrofon 1 das Schallsignal in ein elektrisches Signal umwandelt, welches im Vorverstärker 2 verstärkt wird, danach zur Frequenzgangbeeinflussung das Filter 3 durchläuft und schließlich, nachdem es im Endverstärker 4 auf den erforderlichen Ausgangspegel verstärkt wurde, von einem Lautsprecher 5 wieder in ein akustisches Schallsignal umgewandelt wird. Bei dieser Schaltungsvariante ist das Filter auf konventionelle Weise zwischen zwei Verstärkerstufen angeordnet.Fig. 1 shows a block diagram of a hearing aid according to the invention, wherein the microphone 1 converts the sound signal into an electrical signal, which is amplified in the preamplifier 2, then passes through the filter 3 to influence the frequency response and finally after it in the power amplifier 4 the required output level has been amplified, is converted back into an acoustic sound signal by a loudspeaker 5. In this circuit variant, the filter is arranged in a conventional manner between two amplifier stages.

Fig. 2 zeigt ein Blockschaltbild eines erfindungsgemäßen Hörgerätes, wobei das Filter in der Rückkopplungsschleife eines Verstärkers angeordnet ist. Das Mikrofon 1 wandelt das Schallsignal in ein elektrisches Signal um, welches im Vorverstärker 2 verstärkt wird. Danach durchläuft es den Zwischenverstärker 6, in dessen Rückkopplungsschleife das Filter 3 angeordnet ist, wodurch das Signal frequenzselektiv beeinflußt wird. Danach wird das Signal im Endverstärker 4 auf den erforderlichen Ausgangspegel verstärkt und schließlich vom Lautsprecher 5 wieder in ein akustisches Schallsignal umgewandelt.FIG. 2 shows a block diagram of a hearing device according to the invention, the filter being arranged in the feedback loop of an amplifier. The microphone 1 converts the sound signal into an electrical signal, which is amplified in the preamplifier 2. Then it passes through the intermediate amplifier 6, in the feedback loop of which the filter 3 is arranged, as a result of which the signal is influenced in a frequency-selective manner. Then the signal in the power amplifier 4 is amplified to the required output level and finally converted again by the loudspeaker 5 into an acoustic sound signal.

Fig. 3 zeigt den prinzipiellen Aufbau eines solchen Filters 3. Dieses weist eine biquadratische Struktur auf, wobei die Transistoren T2 und T3 in Verbindung mit dem Widerstand RF1 und dem Kondensator C1, bzw. dem Widerstand RF2 und dem Kondensator C2 zwei Integratoren bilden. Die für eine biquadratische Struktur erforderliche Phasenumkehrstufe wird durch den Transistor T1 und die zugehörigen Widerstände RI2, RX RA1 gebildet. Die Arbeitswiderstände der Transistoren T1 bis T3 sind mit RA1, RA2 und RA3 bezeichnet.Fig. 3 shows the basic structure of such a filter 3. This has a biquadratic structure, the transistors T2 and T3 in conjunction with the resistor R F1 and the capacitor C1, or the resistor R F2 and the capacitor C2 form two integrators . The phase inversion stage required for a biquadratic structure is formed by the transistor T1 and the associated resistors R I2 , R X R A1 . The load resistances of the transistors T1 to T3 are denoted by R A1 , R A2 and R A3 .

Weiters ist der Kollektor des Transistors T3 über den Widerstand Rx auf die Basis des Transistors T1 rückgekoppelt.Furthermore, the collector of transistor T3 is fed back to the base of transistor T1 via resistor R x .

Bei diesem Filter wird die Basis des Transistors T1 als Eingang verwendet, wobei die Kollektorausgänge aller drei Transistoren T1, T2 und T3 als Ausgänge zur Verfügung stehen. Dabei ergibt der Kollektor des Transistors T1 einen Hochpaßausgang (Fig. 4a), der Kollektor des Transistors T2 einen Bandpaßausgang (Fig. 4b) und der Kollektor des Transistors T3 einen Tiefpaßausgang (Fig. 4c). Damit kann dasselbe Filter für verschiedene Anwendungen vorgesehen werden. Die Mittenfrequenz dieses Filters wird dabei durch die Widerstände RF1 und/oder RF2 und die Kondensatoren C1 und C2 festgelegt.With this filter, the base of transistor T1 is used as an input, the collector outputs of all three transistors T1, T2 and T3 being available as outputs. The collector of transistor T1 gives a high-pass output (FIG. 4a), the collector of transistor T2 gives a band-pass output (FIG. 4b) and the collector of transistor T3 gives a low-pass output (FIG. 4c). The same filter can thus be provided for different applications. The center frequency of this filter is determined by the resistors R F1 and / or R F2 and the capacitors C1 and C2.

Bei dem in Fig. 3 dargestellten Filter 3 handelt es sich um eine vereinfachte Kerwin-Huelsman-Newcomb-Struktur, die zur Gruppe der biquadratischen Filter zählt. Durch Anordnung einer weiteren Rückkopplung vom Kollektor des Transistors T2 auf den Emitter des Transistors T1 mittels eines Emitterwiderstandes ist es auch möglich den Gütefaktor des Filters zu verändern und das Filter auf eine volle Kerwin-Huelsman-Newcomb-Struktur aufzuwerten.The filter 3 shown in FIG. 3 is a simplified Kerwin-Huelsman-Newcomb structure which is used for Group of biquadratic filters counts. By arranging a further feedback from the collector of transistor T2 to the emitter of transistor T1 by means of an emitter resistor, it is also possible to change the quality factor of the filter and to upgrade the filter to a full Kerwin-Huelsman-Newcomb structure.

Weiters können alle drei Basisanschlüsse durch drei hochohmige Widerstände zu einem gemeinsamen Eingang verbunden werden. In einem solchen Fall können die Kollektoren der Transistoren T1 oder T3 als Bandpaßausgang verwendet werden. Es ist dann aber kein Hochpaßausgang vorhanden. Eine solche Schaltung entspricht dann einer Tow-Thomas-Struktur, die ebenfalls zu den biquadratischen Filtern zählt.Furthermore, all three basic connections can be connected to a common input using three high-resistance resistors. In such a case, the collectors of transistors T1 or T3 can be used as a bandpass output. But then there is no high-pass exit. Such a circuit then corresponds to a Tow-Thomas structure, which is also one of the biquadratic filters.

Für einen vereinfachten Bandpaß kann die Basis des Transistors T3 allein als Eingang verwendet werden.For a simplified bandpass, the base of transistor T3 can be used alone as an input.

Mit dem Filter 3 nach Fig. 3 und den erwähnten Abänderungen desselben können fast alle Equalizerschaltungen durch entsprechende Auswahl der Impedanzen und Rückkopplungen ausgeführt werden.With the filter 3 according to FIG. 3 and the above-mentioned modifications thereof, almost all equalizer circuits can be implemented by appropriate selection of the impedances and feedback.

Fig. 5 zeigt ein Beispiel für einen Verstärker 6 mit diesem Filter 3. Dabei dient der Transistor T4 mit seinem Arbeitswiderstand R5 als Verstärker, wobei zur Arbeitspunktstabilisierung und Verstärkungseinstellung in bekannter Weise eine Basis-Kollektor-Gegenkopplung über die Widerstände R2 und R3 vorgesehen ist.5 shows an example of an amplifier 6 with this filter 3. The transistor T4 with its load resistor R5 serves as an amplifier, a base-collector negative feedback via the resistors R2 and R3 being provided in a known manner for operating point stabilization and gain adjustment.

Über die Widerstände R4 und R6 ist dieser Verstärker 6 mit dem Filter 3 verbunden, das in der Rückkopplungsschleife des Verstärkers 6 liegt. Dabei bilden die Transistoren T1 bis T3 eine biquadratische Struktur, wobei der Transistor T3 mit dem Widerstand RI2 und dem Kondensator C1 als auch der Transistor T2 mit dem Kondensatop C2 und dem Widerstand RI1 die beiden Integratoren bilden. Die Phasenumkehrstufe wird durch den Transistor T1 mit den Widerständen RF und R7 gebildet. Dabei ist die Verstärkung dieses im Filter 3 angeordneten Verstärkers T1 durch den als Potentiometer geschalteten Widerstand RF veränderbar, wobei sich durch die Änderung der Verstärkung auch eine Verschiebung der Resonanzfrequenz des gesamten Filters 3 ergibt. Die Arbeitswiderstände des Filters 3 sind durch die Widerstände R8, R9 und R10 gebildet.Via the resistors R4 and R6, this amplifier 6 is connected to the filter 3, which lies in the feedback loop of the amplifier 6. The transistors T1 to T3 form a biquadratic structure, the transistor T3 with the resistor R I2 and the capacitor C1 as well as the transistor T2 with the capacitor top C2 and the resistor R I1 forming the two integrators. The phase inversion stage is formed by the transistor T1 with the resistors R F and R7. The gain of this amplifier T1 arranged in the filter 3 can be changed by the resistor R F connected as a potentiometer, the change in the gain also shifting the resonance frequency of the entire filter 3 results. The working resistances of the filter 3 are formed by the resistors R8, R9 and R10.

Der Kollektor des Transistors T3 stellt den Bandpaßausgang des Filters 3 dar, wobei am Kollektor des Transistors T1 ein dazu gegenphasiges Signal abgreifbar ist. Durch das Potentiometer RA können die Amplitude und die Phase des zum Verstärker 6 zurückgeführten Signals beeinflußt werden. Dadurch kann die Rückkopplung des Transistors T4 so gewählt werden, daß, je nach Einstellung des Potentiometers RA, durch positive Rückkopplung (Mitkopplung) eine selektive Anhebung oder durch negative Rückkopplung (Gegenkopplung) eine Absenkung des über das Filter 3 laufenden Signals erreicht wird. Dabei wird die Güte des Filters 3 im wesentlichen durch die Dimensionierung der Widerstände R2, R3 und R4 bestimmt.The collector of the transistor T3 represents the bandpass output of the filter 3, a signal in phase opposition to it being able to be tapped at the collector of the transistor T1. The amplitude and the phase of the signal fed back to the amplifier 6 can be influenced by the potentiometer R A. As a result, the feedback of the transistor T4 can be selected such that, depending on the setting of the potentiometer R A , a positive increase (positive feedback) selective increase or a negative feedback (negative feedback) a reduction of the signal passing through the filter 3 is achieved. The quality of the filter 3 is essentially determined by the dimensioning of the resistors R2, R3 and R4.

Auf diese Weise lassen sich mit nur zwei Einstell-Organen eine nahezu unbegrenzte Vielzahl von Filterkurven realisieren. Diese Einstell-Organe können z.B. manuell bedienbare Potentiometer oder Trimmer sein, ebensogut aber auch durch elektrisch steuerbare Impedanzen, wie z.B. Transistoren gebildet sein.In this way, an almost unlimited number of filter curves can be realized with just two setting elements. These setting elements can e.g. manually operated potentiometers or trimmers, but also just as well by electrically controllable impedances, e.g. Transistors be formed.

Fig. 6 zeigt beispielsweise die Funktion der Schaltung nach Fig. 5, wobei die Mittenfrequenzen der Anhebungen bzw. Absenkungen durch Verstellen des Widerstandes RF gewählt werden können. Die Fig. 6 zeigt nur einige, beliebig herausgegriffene Frequenzgänge, wobei der Verlauf der Kurven oberhalb und unterhalb der Mittellinie angibt, in welchem Umfang bei den einzelnen Frequenzen die Anhebung bzw. Absenkung variiert werden kann.FIG. 6 shows, for example, the function of the circuit according to FIG. 5, the center frequencies of the increases or decreases being able to be selected by adjusting the resistance R F. FIG. 6 shows only a few frequency responses which are picked out arbitrarily, the course of the curves above and below the center line indicating the extent to which the increase or decrease can be varied at the individual frequencies.

Dabei zeigt sich, daß nach den tiefen Frequenzen hin die Verstellmöglichkeit der Absenkung zunimmt und umgekehrt. Dieses Verhalten kommt dem Hörverlust der meisten Schwerhörigen sehr entgegen, die in der Regel eine Absenkung der Tiefen zur Störlärmverminderung und eine Anhebung der Höhen zur Verbesserung der Sprachverständlichkeit benötigen. Fig. 6 zeigt aber auch, daß mit Hilfe der erfindungsgemäß vorgesehenen biquadratischen Filterschaltungen sehr selektive Anhebungen und Absenkungen möglich sind. Durch die Kombination dieses parametrischen Filters mit einem Hoch- und/oder Tiefpaßfilter lassen sich, wie bereits erläutert, alle in der Praxis benötigten Frequenzgänge realisieren.It shows that the adjustment of the reduction increases after the low frequencies and vice versa. This behavior suits the hearing loss of most hearing impaired people, who usually need to lower the depths to reduce noise and raise the heights to improve speech intelligibility. 6 also shows that very selective increases and reductions are possible with the aid of the biquadratic filter circuits provided according to the invention. By combining this parametric filter with a high and / or low pass filter, how already explained, implement all frequency responses required in practice.

Claims (4)

Hörgerät mit einem Mikrofon, mindestens einem von dessen Signal beaufschlagten Verstärker, der zur Beeinflussung des Frequenzganges mit einem Filter höherer Ordnung, das als Mehrfachfilter ausgebildet ist, zusammenwirkt und einem Lautsprecher, der die verstärkten Signale in Schallwellen umwandelt, dadurch gekennzeichnet, daß das Filter (3) eine biquadratische Struktur aufweist und mindestens zwei Integratoren und einen invertierenden Verstärker, bei welchen Bauteilen die aktiven Elemente durch diskrete Bauteile, insbsondere Einzel-Transistoren (T1, T2, T3) gebildet sind, aufweist.Hearing aid with a microphone, at least one amplifier acted upon by its signal, which interacts with a higher-order filter, which is designed as a multiple filter, to influence the frequency response, and a loudspeaker, which converts the amplified signals into sound waves, characterized in that the filter ( 3) has a biquadratic structure and has at least two integrators and an inverting amplifier, in which components the active elements are formed by discrete components, in particular individual transistors (T1, T2, T3). Hörgerät nach Anspruch 1 mit einem mit einer Rückkopplungsschleife versehenen Verstärker, dadurch gekennzeichnet, daß das Filter (3) in der Rückkopplungsschleife des Verstärkers (6) angeordnet ist.Hearing aid according to claim 1 with an amplifier provided with a feedback loop, characterized in that the filter (3) is arranged in the feedback loop of the amplifier (6). Hörgerät nach Anspruch 1 und 2, dadurch gekennzeichnet, daß die einzelnen Stufen des Filters (3) durch eine oder mehrere Rückkopplungsleitungen miteinander verbunden sind.Hearing aid according to claims 1 and 2, characterized in that the individual stages of the filter (3) are connected to one another by one or more feedback lines. Hörgerät nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die Rückkopplungsschleife des Verstärkers (6) über ein einstellbares Potentiometer (RA) zur Einstellung der Filteranhebung oder -absenkung geführt ist und im Filterkreis (3) ein einstellbares Potentiometer (RF) zur Einstellüng der Mittenfrequenz des Filters (3) angeordnet ist.Hearing aid according to one of claims 1 to 3, characterized in that the feedback loop of the amplifier (6) is guided via an adjustable potentiometer (R A ) for setting the filter increase or decrease and in the filter circuit (3) an adjustable potentiometer (R F ) is arranged for setting the center frequency of the filter (3).
EP91890266A 1990-11-07 1991-11-06 Hearing aid with filter circuit Expired - Lifetime EP0485357B1 (en)

Applications Claiming Priority (2)

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AT0223790A AT407103B (en) 1990-11-07 1990-11-07 HEARING AID WITH FILTER CIRCUIT
AT2237/90 1990-11-07

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EP0485357A2 true EP0485357A2 (en) 1992-05-13
EP0485357A3 EP0485357A3 (en) 1993-01-13
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EP91890266A Expired - Lifetime EP0485357B1 (en) 1990-11-07 1991-11-06 Hearing aid with filter circuit

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US (1) US5263089A (en)
EP (1) EP0485357B1 (en)
AT (1) AT407103B (en)
CA (1) CA2054136C (en)
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DK (1) DK0485357T3 (en)

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WO1994010819A1 (en) * 1992-11-03 1994-05-11 Auditory System Technologies, Inc. Hearing aid with permanently adjusted frequency response
DE102022111300A1 (en) 2022-05-06 2023-11-09 Elevear GmbH Device for reducing noise when reproducing an audio signal with headphones or hearing aids and corresponding method

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US8027799B2 (en) * 2007-11-28 2011-09-27 Honeywell International Inc. Digital potentiometer system
WO2021074818A1 (en) * 2019-10-16 2021-04-22 Nuance Hearing Ltd. Beamforming devices for hearing assistance

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WO1994010819A1 (en) * 1992-11-03 1994-05-11 Auditory System Technologies, Inc. Hearing aid with permanently adjusted frequency response
DE102022111300A1 (en) 2022-05-06 2023-11-09 Elevear GmbH Device for reducing noise when reproducing an audio signal with headphones or hearing aids and corresponding method

Also Published As

Publication number Publication date
AT407103B (en) 2000-12-27
DE59107507D1 (en) 1996-04-11
EP0485357A3 (en) 1993-01-13
US5263089A (en) 1993-11-16
EP0485357B1 (en) 1996-03-06
ATA223790A (en) 1994-04-15
CA2054136C (en) 1995-04-25
CA2054136A1 (en) 1992-05-08
DK0485357T3 (en) 1996-05-20

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