Classifications

• • 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
  • H04R25/505—Customised settings for obtaining desired overall acoustical characteristics using digital signal processing
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R2430/00—Signal processing covered by H04R, not provided for in its groups
  • H04R2430/03—Synergistic effects of band splitting and sub-band processing

Definitions

• This invention relates to a method of adapting the transfer function between the sound input and the sound output in a hearing aid to different hearing deficiencies, whereby one measures the hearing defi ⁇ ciency and produces a digital signal which indicates the hearing deficiency or the desired correction of the transfer function, after which the digital signal produced is introduced into a memory in the hearing aid, and this method can be effected in a hearing aid with a sound detecting amplifier, an amplifier cir ⁇ cuit and sound reproducing device, said apparatus having a memory in which a measure of the user's hearing deficiency or the desired correction of the transfer function of the apparatus is stored as a digital signal.
• a method and apparatus which uses the digitalization of au io, signals for use in hearing aids is known from the USA patent no. 4,187,413. With the technique known from this patent one converts the whole of the desired audible signal to digital signals, and cor ⁇ rects the signal by means of a programme which is supplied to the hearing aid in the form of a digital signal. The corrected digital signal is then conver— ted to an analogue signal which is amplified and re ⁇ produced in the hearing aid's receiver.
• the object of the invention according to the present application is to be able to digitalize the whole of the control and regulation function, without the nec- essity of having to convert the whole of the audible signal to digital values, whereby the desired effect can be achieved with a modest power consumption, thus making it possible to build the whole of the appara ⁇ tus into an ordinary hearing aid.
• the audible sig- nal that is the signal which the user must have am- - plified or changed, is processed in the hearing aid as an ordinary analogue signal, i.e., it is subjected to suitable amplification, while the whole of the control takes place digitally. If one proceeds as presented in claim 2, one can also use the digital hearing deficiency signal to control the filter limits for each frequency range, which provides increased possibilities of adaption.
• the apparatus for the execution of the method is ex ⁇ pediently driven in multiplex operation as presented in the claims 5 and 6. It is thus possible to use the same circuit to convert the average values for all the frequency ranges to signals for use in the con ⁇ trol of the amplifiers.
• That digital signal which is indicative of the hear ⁇ ing deficiency or the desired correction of the tran- sfer function can also be used to control the cutoff frequencies of the filters and the adjustments of the attentuators, as presented in claims 8 and 9. This can be effected simply by having a small memory for adjusting the relevant circuits. The contents of the memory can be changed when desired by reading a new programme into the hearing aid.
• the drawing shows a schematic block diagram covering the whole of the hearing aid with associated digital regulation circuit. It comprises sound inputs 1, 2 and 3, where 1 shows the audio input from radio, 2 shows the audio input through an ordinary microphone and 3 shows the audio input by means of a so-called telecoil.
• the audio signal received is first ampli- fied in a normal amplifier 4, after which it is fed to an analogue filter bank 5, 6, 7 and 8.
• the filter, bank shown here as an example consists of four fil ⁇ ters which divide the signals received into four fre ⁇ quency ranges.
• the individual filters 5, 6, 7 and 8 are digitally controllable, i.e. their filter limits can be changed as a function of digital signals sup ⁇ plied to the filters from a control circuit 47, in which information can be stored concerning the filter limits.
• the control circuit 47 thus contains a store for digital data.
• the frequency ranges co ing from the filters are fed to each their channel 9, 10, 11 and 12 which lead to the amplification circuit 32, 33, 34 and 35, which will be explained later.
• rectification circuit 13, 14, 15 and 16 from each of the channels 9, 10, 11 and 12 there is taken a signal which repre ⁇ sents the average value of the signal in each of said channels.
• the circuits 13, 14, 15 and 16 each contain a full-wave rectifier and a circuit which calculates the average value of the signal.
• This average value is fed to an analogue multiplexer 17 which is con ⁇ trolled by a control circuit 46.
• the multiplexer 17 feeds the average values alternately to a logarithmic amplifier 18.
• the logarithmic amplifier 18 converts the average values to signals which represent the signal value in deciBel. This conversion of the cal ⁇ culated average values to measures indicated in dB is undertaken because the normal dynamic range for ordinary audible sound is of 80/90 dB. It is there ⁇ fore easier to carry out the subsequent regulation on the basis of a measurement in dB than on the basis of a measurement indicated in linear values.
• a cir ⁇ cuit 19 which is a so-called sample and hold circuit. This circuit is included in order to hold the signals while they are being supplied to the analog-digital converter 20, in that the signal must be held for a as long as the .converter is operating.
• the circuit 19 and 20 are controlled from the same control circuit 46 as the control multiplexer.
• the signal from the analog-digital converter is fed to a correction cir ⁇ cuit 21 which contains a memory.
• a correction cir ⁇ cuit 21 which contains a memory.
• This memory is stored a table covering the dynamic conditions for. each channel.
• This stored information indicates the hearing deficiency of the user of the hearing aid or indicates the desired correction of the hearing aid's transfer function.
• the information is read into the store at point B, from where through a circuit 44 which, for example, can be a series to parallel con ⁇ verter, it is transferred to the correction circuit 21. From the drawing it will be seen that the control circuit 46 not only controls the multiplexer 17, but also the correction circuit 21 with memory.
• the measured average value signals are compared with the stored data for the user's hearing deficiency, thus giving rise to correction data dependent upon the hearing deficiency.
• This cor- rection data is fed to a digital-analog converter 22, from where it is fed to a second analog-multiplexer 23. From here the data is distributed to sample and_ hold circuits 24, 25, 26 and 27.
• the analogue signal is still an indica-
• the thus amplified signals ' are fed to • a summation amplifier 40 where they are added and fed, for example, through a gain control 41 to a speech amplifier 42 before being fed to the normal sound-reproducing earphone in the hearing aid.
• an attenuator 36, 37, 38 and 39 can be inserted in each amplification channel between the controllable amplifiers 32, 33, 34 and 35 and the summation amplifier 40.
• These attenuators are simil ⁇ arly adjustable by means of an adjusting circuit 45, and said adjusting circuit can also contain a store for digital information.
• the information which is read in at B can be fed direct to the memory of adjusting circuit 45 through the series to parallel converter 44. In the memory of adjusting circuit 45 is thus stored infor ⁇ mation concering the adjustment of the attenuators 36, 37, 38 and 39.
• the information which is read in at point • B can be fed to the control circuit 47, which also contains a store with information concerning the ad- justment of the filter bank.
• This transfer of inform ⁇ ation is effected by connecting the two points marked A to each other.
• the hearing deficiency is con ⁇ verted to digital values which, in the form of a dig ⁇ ital electrical signal, are read into the hearing aid at point B.
• the information concerning the hearing deficiency is thus stored partly in the memory of correction circuit 21 and partly in the memories of the two -.circuits 45 and 47.
• the store of information in 45 provides for the adjustment of the attenuators 36, 37, 38 and 39
• the store 47 with control cir ⁇ cuit provides for the adjustment of the filter limits in the filter bank 5, 6, 7 and 8.
• the memory contained in the correction circuit 21 can be a so-called EEPROM (electrically erasable program ⁇ mable read only memory) , i.e. a read memory, the con ⁇ tents of which can be changed.
• EEPROM electrically erasable program ⁇ mable read only memory
• the in ⁇ formation is stored in the correction circuit 21 as a kind of table covering the dynamic conditions for each channel.
• the hearing aid thus achieved is one which can be adapted to almost all hearing deficiences.

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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)
• Circuit For Audible Band Transducer (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8142672

Family Applications (1)

Country Status (3)

Cited By (17)

Citations (2)

• 1981
  • 1981-12-10 DK DK546581A patent/DK546581A/da not_active Application Discontinuation
• 1982
  • 1982-12-03 EP EP19830900018 patent/EP0097184A1/en not_active Withdrawn
  • 1982-12-03 WO PCT/DK1982/000107 patent/WO1983002212A1/en not_active Application Discontinuation

Patent Citations (2)

Non-Patent Citations (1)

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