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
  • H04R3/005—Circuits for transducers, loudspeakers or microphones for combining the signals of two or more microphones
• • 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
  • H04R25/40—Arrangements for obtaining a desired directivity characteristic
  • H04R25/407—Circuits for combining signals of a plurality of transducers
• • 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

Definitions

• the present invention has the object to propose an improved method for manufacturing at least one output electric audio signal by processing at least one input electric audio signal.
• the present invention departs from recognitions which have been made by the inventors in context with beam-forming at hearing devices, but may be significantly generalized.
• a hearing device which is worn at least adjacent to an individual's one ear with the object to improve individual's acoustical perception. Such improvement may also be barring acoustical signals from being perceived in the sense of hearing protection for the individual. If hearing devices are worn on both individual's ears and are in mutual communication, then we speak of the hearing devices of a binaural hearing system. A hearing device may further be a device to positively improve individual's acoustical perception, whether such individual has an impaired perception or not. If the hearing device is tailored so as to improve the perception of a hearing-impaired individual then we speak of a hearing aid device. With respect to the application area a hearing device may especially be applied behind the ear, completely in the ear canal or may even be implanted.
• Beam-forming is a well-known method e.g. used to increase the signal-to-noise ratio in acoustical environment.
• the beam-shaped amplification characteristic in polar coordinate representation is realized by combining the sound pressure information, which is retrieved at different loci having a known mutual distance. The sound pressure is thereby sensed at these loci by respective acoustical-to- electrical converters.
• the skilled artisan perfectly knows e.g. beam-forming following the delay-and-add principal.
• beam-forming techniques are known e.g. from the US 6 522 756, US 6 603 861, US 6 449 216, US 6 865 275, WO 99/04598, all from the same applicant as the present application. Thereby, it is perfectly known that signal processing is performed either in time-domain, in today' s processing art mostly after analog-to-digital conversion, or in frequency-domain which necessitates previous analog-to-digital signal conversion.
• the beam-forming takes place in reverberant acoustical environment and on the head of an individual.
• Characteristics which limit beam-forming quality achievable are especially level mismatch and phase mismatch at the input acoustical-to-electrical converters.
• phase difference of acoustical signals impinging upon the input converters is the decisive parameter for directivity indication and level mismatch may be considered as due to an amplification setting, both, phase and level mismatch of the input converters leads to deterioration of the achievable beam-forming characteristic.
• the addressed mismatch may be dependent on direction of arrival of the impinging acoustical signals and is frequency-dependent.
• phase and level mismatch may accurately be compensated in time-domain.
• processing low-frequency signals in the frequency-domain mode leads to relatively bad beam-forming quality, as no accurate phase matching is possible.
• the object as addressed above is resolved by the present invention by a method for manufacturing at least one output electric audio signal, by processing at least one input electric audio signal, whereby the input electric audio signal comprises a first part and a second part which is different from the first part.
• the addressed processing thereby comprises separating the two parts and processing in frequency-domain at least the first part and in time-domain only the second part. Thereby, from the two parts as addressed time-domain processing is only applied to one thereof. Processing in frequency-domain is applied to the second part, but additionally and as will be seen the first part may also be additionally processed in frequency-domain. Latter may be done e.g. just to achieve the same time lag for the second part as is occurring to the first part due to frequency- domain processing.
• one part of the signal to be processed is processed in time-domain, the other part in frequency-domain, and the respective selection is made so as to optimally exploit the advantages of the two domain processings for the respective signal parts.
• a hearing device with a main signal processing path and a side signal path.
• the main signal processing path includes signal processing in frequency-domain mode and thus provides for a relatively large group delay.
• the side signal path provides no processing, but provides for undelayed time-domain signal transfer.
• the results of frequency-domain processing in the main signal path and of the unprocessed time-domain signal of the side path are summed leading to a significant reduction of overall time delay for an individual perceiving an acoustical signal. This improves individual's ability to localize acoustic sources in spite of wearing a hearing device.
• the two parts in which the input audio signal is separated consist of spectrally different components.
• the two domain processings have respective advantages specifically for different frequency bands of audio signals.
• the addressed separating of the two parts is performed by filtering.
• the first signal part which is only processed in frequency-domain consists of higher-frequency components, whereby the second part, which is processed in time-domain, comprises lower-frequency components.
• the band separation for higher and lower frequencies is applied for audio signals at about 1 kHz so that the addressed higher frequencies are predominantly higher than 1 kHz and the addressed lower frequencies are predominantly lower than 1 kHz.
• the at least one input electric audio signal is at least dependent from an output signal of an input acoustical-to-electrical converter arrangement of a hearing device.
• the input signal to an electrical-to- mechanical converter arrangement of a hearing device is made at least dependent from the addressed output electric audio signal.
• the at least one input electric audio signal is at least dependent on an output signal of an input acoustical-to-electrical converter arrangement of a hearing device, and an input signal to an electric-to-mechanical converter arrangement of a further hearing device is made at least dependent from the output electric audio signal and the one and the further hearing devices are selected to be one and the same hearing device.
• the addressed method is implied with respect to input and output converters at one hearing device considered.
• the addressed processing comprises beam-forming.
• processing in time-domain and processing in frequency-domain are in fact equal processings, but respectively performed in time and frequency-domain.
• both processings are beam-forming processings and e.g. by delay-and-add method, and are applied in time-domain as well as in frequency-domain.
• the at least one input electric audio signal comprises at least two electrical audio signals respectively dependent on an electric output signal of an acoustical-to-electrical converter .
• FIG. 1 by means of a simplified signal flow/functional block diagram the method according to the present invention performed for beam-forming processing an input audio signal which is generated by an input acoustical-to-electrical converter arrangement;
• Fig. 2 the processing according to fig. 1 under a more generalized aspect;
• Fig. 3 in a representation in analogy to that of fig. 1, processing of the output signal of an acoustical- to-electrical converter arrangement in the two domains specifically for mismatch compensation, and
• Fig. 1 there is shown by means of a simplified functional block/signal flow diagram a specific embodiment according to the present invention, wherein signal processing is beam-forming at a or for a hearing device.
• an input acoustical-to-electrical converter arrangement 1 which, generically, generates an output electric audio signal S 1n , input signal for subsequent processing.
• This signal is dependent from acoustical signals impinging on a converter array of the at least two converters Ia and Ib of the arrangement 1.
• the two parts S ini and S ⁇ n2 are formed by the higher-frequency components and of the lower-frequency components respectively of both signals S a and S b .
• the output signal of converter 1 with the two components S a and S b is separated by respective highpass and lowpass filters HP a , HP b and LP a , LP b , into the two parts of higher-frequency content and of lower- frequency content.
• the respective time delays ⁇ a and ⁇ b are introduced.
• respective beams characteristics are realized, e.g. respective forwards and rearwards cardioid beam patterns.
• the two beam-characteristic signals which are the result of time-domain beam-forming in unit 3 are output from processing unit 3.
• the beam-characteristic lower-frequency signal S Pb is summed at Q 4 with the higher-frequent component S HPb from the output signal of converter Ib.
• the lower-frequency time-domain beam-formed signal Sp 3 is summed at Q 3 with the higher-frequency component S HPa .
• the summing result of Q 3 and Q 4 are both time-to-frequency converted at unit 7a, 7b.
• the high-frequency components yet not processed are subsequently processed in frequency- domain beam-processing ⁇ P a and (% > , wherein e.g. the same beam-forming process is performed as in unit 3 but now in frequency-domain. As shown in fig.
• the result signal of such time- domain beam-forming process is summed to the second signal part which consists of higher-frequency components.
• the summing result is subjected to frequency-domain beam- forming after respective time-to-frequency-domain conversion as is perfectly clear to the skilled artisan.
• phase mismatch compensation is achieved for the lower-frequency part. Also level mismatch of the input converters is compensated in time-domain processing of the lower-frequency part.
• the approach of combining time-domain and frequency-domain signal processing in fact in parallel on specific parts of a signal allows to selectively apply the optimum domain processing.
• lower-frequency parts are advantageously time- domain processed and higher-frequency parts are advantageously frequency-domain processed.
• Such an approach may be of high advantage for signal processing more generically than just for beam-forming.
• the electrical audio input signal Si n is separated at a unit 17 into two parts S ⁇ ni and Si n 2.
• the second part Sj .n 2 is processed in time-domain P at unit 19 and the result is summed to the first part Si nI a" t Q 34 .
• Both the unprocessed first part Si n i and the time-domain processed second part SP are then processed in frequency-domain in unit 21.
• the acoustical-to-mechanical input converter arrangement 1, the output electrical-to-mechanical converter arrangement 13 as well as all the processing as shown may be incorporated within one single hearing device. Nevertheless, the converter arrangement 1 and 13 may also be incorporated in two distinct hearing devices, e.g. of a binaural system. One or both converter arrangements 1, 13 may be provided at a hearing device and processing may be performed remote. Thus, time-domain and frequency-domain processing may be performed in a centralized processing architecture or in a decentralized, possibly with wireless intercommunication of the processes or units. In other words utmost flexibility is possible with respect to the architecture of the embodiment as shown in fig. 1.
• one of the important considerations to decide which part of an electric audio signal is to be processed in time-domain and which part is to be processed in frequency-domain is matching of the input acoustical-to- electrical converters as of Ia and Ib. If matching is the only topic to be resolved before further signal processing, which further processing may be realized in either of the two domains without specific preference, the signal processing as shown in fig. 3 may be performed. Here parallel time-domain and frequency-domain processing is performed. According to fig. 3 the two components S a and S b of Si n are again and as was explained in context with fig. 1 separate in two parts, the lower-frequency part SLP and the higher-frequency part S H p. The former is processed to compensate for low-frequency mismatch of the converters Ia and Ib in time-domain matching unit 33.
• time-to-frequency conversion as well as frequency-to-time-domain conversion has been omitted for simpleness .
• unit 35 two matched high-frequency signals are generated.
• the lower-frequency matched signal S LPM and the higher-frequency matched signal S HPM ⁇ after respective conversion and/or reconversion, are summed, resulting in output signals S ou ta and S ou tb-
• the signals S O ⁇ is further processed, be it in time or in frequency-domain to establish the desired transfer characteristic between input acoustical signal Si n and output mechanical signal of a hearing device.
• fig. 4 there is shown, in analogy to fig. 2, the more generalized processing as of fig. 3.
• the electric audio input signal Si n is separated in a first part Si n i and a second part Si n2 .
• the first part is frequency-domain processed as shown by ⁇ P, whereas the second part is processed in time-domain, P.

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• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Otolaryngology (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Neurosurgery (AREA)
• Circuit For Audible Band Transducer (AREA)
• Stereophonic System (AREA)

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• 2006
  • 2006-05-19 WO PCT/CH2006/000263 patent/WO2006114015A2/en active Application Filing
  • 2006-05-19 EP EP06721965A patent/EP2025200A2/de not_active Withdrawn

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