EP0471083A1
Expired / Lapsed
EP
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Speaking device having hand-free conversational function
Assignee: Fujitsu Ltd
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Filing: 1991-02-16
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Granted: —
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Expires: 2011-02-16
Abstract
Abstract This invention relates to a speaking device having a hand-free conversation function which comprises an echo canceler (3) that can cancel the echo given by the direct acoustic coupling between a speaker and a microphone caused by a system comprising the case of the device and the grounded surface thereof and a speech switching circuit (6) in which insertion loss of speech signal is so set that its upper limit is equal to the sufficient attenuation quantity for cancelling the echo caused by the indirect acoustic coupling determined by the spatial state where the speaking device is used. A good speech quality is obtained with the processing circuit of a low cost and small size by assigning the optimum shares of the functions to the echo canceler (3) and the speech switching circuit (6) respectively.
Inventors
- 👤 Juro Ohga
- 👤 Hiroyuki Masuda
- 👤 Kensaku Fujii
- 👤 Yoshihiro Sakai
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 08:47
CPC Classifications
H; H04; H04M; H04M9/00; H04M9/08; H04M9/082
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
140 words
A speaking apparatus which has a handfree conversation function enabling speaking without holding a receiver in the hand by providing a microphone (1) and a speaker (2) in the casing, said speaking apparatus having a handfree conversation function characterized by being provided with a first echo canceler (3) which can cancel an echo given by direct acoustic coupling between the speaker (2) and the microphone (1) caused by a system comprised of a casing (9) and a surface on which the casing (9) is emplaced and a speech switching circuit (6) in which the amount of insertion attenuation of a transmitted and received signal is set with an upper limt of the amount of attenuation sufficient for cancellation of the echo given by indirect acoustic coupling determined from the state of the space in which the speaking apparatus is used.
Claim 2
Dependent Claim
33 words
A speaking apparatus having a handfree conversation function as set forth in claim 1, further provided with a second echo canceler (4) which can cancel echo arising in an anti-side tone circuit (5).
Claim 3
Dependent Claim
36 words
A speaking apparatus having a handfree conversation function as set forth in claim 1, characterized in that the echo cancellable reverberation time of the first echo canceler (3) is set to be less than 20 msec.
Claim 4
Dependent Claim
43 words
A speaking apparatus having a handfree conversation function as set forth in claim 1, characterized in that the cancellable reverberation time of the first echo canceler (3) is set to about the reverberation time actually measured in an anechoic room, anechoic chamber, etc.
Claim 5
Dependent Claim
46 words
A speaking apparatus having a handfree conversation function as set forth in claim 2, characterized in that the cancelable reverberation time of the second echo canceler (4) is set to a continuous time of equal to or less than that of the first echo canceler (1).
Claim 6
Dependent Claim
40 words
A speaking apparatus having a handfree conversation function as set forth in claim 2, characterized in that an upper limit of an amount of insertion attenuation of the speech switching circuit (6) is set to a degree enabling two-way speaking.
Claim 7
Dependent Claim
37 words
A speaking apparatus having a handfree conversation function as set forth in claim 6, characterized in that an upper limit of an amount of insertion attenuation of the speech switching circuit (6) is set to 20 dB.
Claim 8
Dependent Claim
137 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that at least one of the first echo canceler (3) and the second echo canceler (4) is provided with a coefficient correcting means (130) which transmits a signal to a system with unknown characteristics and estimates, based on the difference between the echo with respect to that signal obtained at an input terminal receiving the reply and a pseudo echo synthesized from that signal using an adaptive filter (120) provided in the apparatus and the filter input, the coefficient of that adaptive filter and a coefficient selecting means (150) which suspends the coefficient correction processing for the adaptive filter at a frequency in accordance with a predetermined rule so as to reduce the amount of processing performed for each sampling period.
Claim 9
Dependent Claim
41 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that the said coefficient selecting means (150) is provided with a means for suspending the coefficient correction processing each tap of the adaptive filter (120).
Claim 10
Dependent Claim
46 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that the said coefficient selecting means (150) is provided with a means for suspending the coefficient correction processing in units of sets of several taps of the adaptive filter (120).
Claim 11
Dependent Claim
94 words
A speaking apparatus having a handfree conversation function as set forth in claim 9, characterized in that the means for suspending the coefficient correction processing for each tap is provided with a means which assumes that the amplitude characteristic of the impulse response falls exponentially with respect to the predicted reverberation time of the unknown system and, when giving step input to a low pass filter haivng a filter coefficient giving the desired ability to suppress external disturbance, suspends the estimation operation for each tap of the adaptive filter which has a small response.
Claim 12
Dependent Claim
119 words
A speaking apparatus having a handfree conversation function as set forth in claim 10, characterized in that the means for suspending operation in units of sets of several taps is provided with a means which assumes the amplitude characteristic of the impulse response falls exponentially with respect to a predicted reverberation time of an unknown system, gives as a step input to a low pass filter (120) having a filter coefficient giving a desired ability to suppress external disturbances the average value of the set of taps of the adaptive filter (120) or one of the values in that combination as the amplitude value, and suspends the estimation operation for the ones with the small response at that time.
Claim 13
Dependent Claim
161 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that the said coefficient selecting means (150) has, as a means, provided in an apparatus which sends a signal to a system with unknown characteristics, estimates the transmission function which the system gives from the response, and forms a transmission function equivalent to the same, detecting that the signal transmitted to the system is a narrow band signal for which the estimation is to be suspended, a coefficient calculating means which calculates the value of the coefficient to give a minimum difference between the output of a secondary noncyclic type filter comprised of a shift register giving a delay of one sampling period and a multiplier which multiplies with a separately determined coefficient and a filter input, which coefficient correcting means uses as the correction constant in the coefficient calculating means a value corresponding to the detection delay allowable in the narrow band signal detection.
Claim 14
Dependent Claim
178 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that the coefficient selecting means (150) has, as a means, provided in an apparatus which sends a signal to a system with unknown characteristics, estimates the transmission function which the system gives from the response, and forms a transmission function equivalent to the same, detecting that the signal transmitted to the system is a narrow band signal for which the estimation is to be suspended, a coefficient calculating means which calculates the value of the coefficient to give a minimum difference between the output of a secondary noncyclic type filter comprised of a shift register giving a delay of one sampling period and a multiplier which multiplies with a separately determined coefficient, which coefficient correcting means uses the fact that the ratio between a level of difference and a level of the filter input becomes less than a fixed value determined in advance and gives in a fixed manner the secondary coefficient of the secondary noncyclic circuit filter at 1 or -1.
Claim 15
Dependent Claim
180 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that the said coefficient selecting means (150) has, as a means, provided in an apparatus which sends a signal to a system with unknown characteristics, estimates the transmission function which the system gives from the response, and forms a transmission function equivalent to the same, detecting that the signal transmitted to the system is a narrow band signal for which the estimation is to be suspended, a coefficient calculating means which calculates the value of the coefficient to give a minimum difference between the output of a secondary noncyclic type filter comprised of a shift register giving a delay of one sampling period and a multiplier which multiplies with a separately determined coefficient, which coefficient correcting means uses the fact that the ratio of the level of difference level and the level of the filter input becomes less than a fixed value determined in advance and performs the calculation of the signal level of the narrow band signal by cumulative addition divided into sections.
Claim 16
Dependent Claim
145 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that the said coefficient selecting means (150) has, as a means, provided in an apparatus which sends a signal to a system with unknown characteristics, estimates the transmission function which the system gives from the response, and forms a transmission function equivalent to the same, detecting that the signal transmitted to the system is a narrow band signal for which the estimation is to be suspended, a coefficient calculating means which calculates the value of the coefficient to give a minimum difference between the output of a secondary noncyclic type filter comprised of a shift register giving a delay of one sampling period and a multiplier which multiplies with a separately determined coefficient and the filter input, which coefficient correcting means resets the coefficient value at every fixed interval.
Claim 17
Dependent Claim
172 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that the said coefficient selecting means (150) has, as a means, provided in an apparatus which sends a signal to a system with unknown characteristics, estimates the transmission function which the system gives from the response, and forms a transmission function equivalent to the same, detecting that the signal transmitted to the system is a narrow band signal for which the estimation is to be suspended, a coefficient calculating means which calculates the value of the coefficient to give a minimum difference between the output of a secondary noncyclic type filter comprised of a shift register giving a delay of one sampling period and a multiplier which multiplies with a separately determined coefficient and the filter input, which coefficient correcting means uses the fact that the ratio of the level of difference and the level of filter input becoems less than a fixed value determined in advance and resets the coefficient value at every fixed interval.
Claim 18
Dependent Claim
146 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that the said coefficient selecting means (150) has, as a means, provided in an apparatus which sends a signal to a system with unknown characteristics, estimates the transmission function which the system gives from the response, and forms a transmission function equivalent to the same, detecting that the signal transmitted to the system is a narrow band signal for which the estimation is to be suspended, a narrow band signal detecting means using a secondary noncyclic type filter comprised of a shift register giving a delay of one sampling period and a multiplier which multiplies with a separately determined coefficient, which narrow band signal detecting means inserts into the telephone circuit a filter equivalent to the secondary noncyclic type filter when it judges a signal is a narrow band signal.
Claim 19
Dependent Claim
202 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that the said coefficient selecting means (150) has, as a means, provided in an apparatus which sends a signal to a system with unknown characteristics, estimates the transmission function which the system gives from the response, and forms a transmission function equivalent to the same, detecting that the signal transmitted to the system is a narrow band signal for which the estimation is to be suspended, a coefficient calculating means which calculates the value of the coefficient to give a minimum difference between the output of a secondary noncyclic type filter comprised of a shift register giving a delay of one sampling period and a multiplier which multiplies with a separately determined coefficient and the filter input, which coefficient correcting means uses the fact that the ratio of the level of the difference and the level of the filter input becomes less than a fixed value determinated separately, adds to the differential output a primary cyclic filter having as a coefficient 1/2 of the primary coefficient of the secondary noncyclic type filter which is extracted, and uses the output for the calculation of the level ratio.
Claim 20
Dependent Claim
138 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that the said coefficient selecting means (150) has, as a means, provided in an apparatus which sends a signal to a system with unknown characteristics, estimates the transmission function which the system gives from the response, and forms a transmission function equivalent to the same, detecting that the signal transmitted to the system is a narrow band signal for which the estimation is to be suspended, a narrow band signal detecting means using a secondary noncyclic type filter comprised of a shift register giving a delay of one sampling period and a multiplier which multiplies with a separately determined coefficient, which narrow band signal detecting means performs in block units the coefficient renewal processing during the arithmetic operations for estimating the coefficient.
Claim 21
Dependent Claim
203 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that the said coefficient selecting means (150) has, as a means, provided in an apparatus which sends a signal to a system with unknown characteristics, estimates the transmission function which the system gives from the response, and forms a transmission function equivalent to the same, detecting that the signal transmitted to the system is a narrow band signal for which the estimation is to be suspended, a coefficient calculating means which calculates the value of the coefficient to give a minimum difference between the output of a secondary noncyclic type filter comprised of a shift register giving a delay of one sampling period and a multiplier which multiplies with a separately determined coefficient and the filter input, which coefficient correcting means uses the fact that the ratio of the level of the difference and the level of the filter input becomes less than a fixed value determined separately, constitutes a secondary cyclic type filter from a separately determined constant determining the band width, connects input of the secondary noncyclic type filter to the filter input, and uses the resultant output for the calculation of the level ratio.
Claim 22
Dependent Claim
145 words
A speaking apparatus having a handfree conversation function as set forth in claim 8, characterized in that the said coefficient selecting means (150) has, as a means, provided in an apparatus which sends a signal to a system with unknown characteristics, estimates the transmission function which the system gives from the response, and forms a transmission function equivalent to the same, detecting that the signal transmitted to the system is a narrow band signal for which the estimation is to be suspended, a narrow band signal detecting means using a secondary noncyclic type filter comprised of a shift register giving a delay of one sampling period and a multiplier which multiplies with a separately determined coefficient, which narrow band signal detecting means inserts into the telephone circuit the secondary nonroving type filter for the first time after the detection results continue a number of times.
References Cited (Backward Citations)
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