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JP2015177546

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DESCRIPTION JP2015177546
Abstract: To provide a hearing aid that generates a transmission signal with reduced wind noise
by parallel processing of filters with small delay. Kind Code: A1 A listening apparatus includes
microphones 12, 13 and supplies them to an analog / digital converter 14, 15, and obtains a first
microphone signal ms1 and a second microphone signal ms2. The 48 channels are divided by the
filter banks 16 and 17 and supplied to the wind noise evaluation unit 18 and the converter 22.
The filter banks 19 and 20 divide the signal into four channels, and pass through the beam
forming device 21. In the multiplier 23, the second filter signal fs2 is multiplied by the parameter
fp belonging thereto and supplied to the adder 24, and the transmitter 25 Receive a transmission
signal. [Selected figure] Figure 3
Method of generating transmission signal with reduced wind noise with reduced latency
[0001]
The present invention relates to a method for generating a transmission signal based on a windblocked useful signal that can be transmitted from a listening device to an external device. In this
case, the first and second microphone signals are generated from the effective signal disturbed
by the wind of the listening device, and both microphone signals are filtered by the filter system
having the first latency, whereby the first filtered signal Is obtained. A parameter capable of
reducing the wind component from both microphone signals is calculated from the first filter
signal. The invention further relates to a listening device for generating transmission signals as
well. Here, the listening device is understood as any device that can be worn in or on the ear and
generates an acoustic stimulation, in particular a hearing aid, a headset, headphones etc.
03-05-2019
1
[0002]
Hearing aids are portable listening devices that help the deaf person. In order to meet a large
number of individual requirements, a back ear hearing aid (HdO), a hearing aid with an external
receiver (RIC: receiver in canal) and an in-ear hearing aid (IdO), such as a concha hearing aid or
canal hearing aid (ITE, CIC) Hearing aids of various constructions such as) are provided. The
hearing aids mentioned by way of example are worn in the outer ear or in the ear canal. In
addition, bone conduction hearing aids, implantable or vibrotactile hearing aids are commercially
available. At that time, the stimulation to the damaged hearing is performed mechanically or
electrically.
[0003]
The hearing aid in principle comprises as main components an input converter, an amplifier and
an output converter. The input transducer is generally an acoustic receiver such as a microphone
and / or an electromagnetic receiver such as an induction coil. The output transducers are mostly
electroacoustic transducers, such as small loudspeakers or electromechanical transducers, such
as bone conduction receivers. The amplifier is usually incorporated in the signal processing unit.
An example of this principle structure is shown in FIG. The hearing aid casing 1 for mounting
behind the ear incorporates one or more microphones 2 for picking up sound from the
surroundings. Similarly, the signal processing unit 3 incorporated in the hearing aid casing 1
processes and amplifies the microphone signal. The output signal of the signal processing unit 3
is transmitted to a speaker or receiver 4 that outputs an acoustic signal. The sound is optionally
transmitted to the tympanic membrane of the hearing aid wearer via an acoustic tube fixed in the
ear canal by the ear formations. The energy supply of the hearing aid and in particular the
energy supply of the signal processing unit 3 is likewise provided by the battery 5 integrated in
the hearing aid housing 1.
[0004]
Wind noise is a problem for hearing aids and in particular hearing aids equipped with a back ear
hearing aid or an external microphone. When such hearing aid signals are used in other devices,
other systems, etc., eg other hearing aids (especially for binaural noise reduction) or in headsets,
the wind noise in the signal to be transmitted is It is advantageous to be reduced. Wind noise can
usually be reduced in two ways, most of which are used simultaneously. -Set the directional
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2
characteristics of the directional microphone to omnidirectional. -Application of amplification
dependent on frequency and also on the estimated wind strength in the corresponding frequency
band.
[0005]
Wind noise is a very strong function of frequency. This can be seen from FIG. First of all, as the
wind strengths w1 to w4 rise, the acoustic output of the lower and middle frequencies of the
audible spectrum increases. It is advantageous, based on frequency dependence, to estimate wind
over frequency, for example by means of a Wiener filter, and to reduce the amplitude of the
frequency band appropriately.
[0006]
Such disturbance noise reduction requires a filter bank or a configurable high-pass filter. Most
filter banks for channel specific processing in hearing aids use 16 to 48 channels. However, this
results in long latency in the signal in question. That is, based on the large number of channels, a
steep slope filter is required which requires a certain degree of filter length. Correspondingly, the
delay is increased. However, a high resolution filter bank, having for example 48 channels, has
the advantage that the wind can be detected accurately. In practice, such wind detection is only
the first step for mono-ear wind noise reduction. However, if such a filter bank is used to reduce
wind noise in the signal (ie to reproduce the time signal which must be applied to the
amplification and applied to the other hearing aid) Can not accept an additional delay or latency
of about 4-5 ms for application in a binaural system.
[0007]
It is an object of the present invention to find out the possibility of reducing wind noise in a
listening system where a signal transmission of the useful sound is required.
[0008]
According to the invention, this task generates first and second microphone signals consisting of
wind-disturbed effective signals in a listening device and filtering both microphone signals by a
first filter system having a first latency time. A first filtered signal is thereby obtained, and
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independent of the first filtered signal, by obtaining a transmission signal disturbed by the wind
from one or both of the two microphone signals, as well as a transmission signal disturbed by the
wind By reducing the components of the wind and obtaining the transmission signal, the method
is solved by a method for generating a transmission signal that can be transmitted from the
listening device to an external device based on the wind-blocked valid signal. Ru.
That is, the present invention is a method for generating a transmission signal based on an
effective signal disturbed by wind in a listening device and capable of being transmitted from the
listening device to an external device, wherein the interference is caused by wind in the hearing
device. First and second microphone signals are generated from the selected effective signal, and
the first and second microphone signals are branched into a first branch line and a second
branch line parallel thereto, and a second branch line branched into the first branch line The first
and second microphone signals are filtered by a first filter system having a first latency, whereby
a first filtered signal is obtained, and the first and second microphone signals branched into a
second branch line Alternatively, it is characterized in that a component of wind is reduced from
the signal based thereon by using the first filter signal to obtain a transmission signal.
[0009]
According to the invention, furthermore, the microphone arrangement for generating the first
and the second microphone signal consisting of the effective signal disturbed by the wind in the
listening device and filtering both microphone signals to obtain a first filtered signal A first filter
system having a first latency, and a processing unit for obtaining a transmission signal disturbed
by wind from one or both of the two microphone signals independently of the first filter signal; A
wind noise reduction device is provided to reduce the components of the wind from the
disturbed transmission signal to obtain the transmission signal, based on the wind disturbed
effective signal, which can be transmitted from the listening device to an external device A
listening device for generating a transmission signal is provided. That is, the present invention is
a listening device for generating a transmission signal that is based on a wind-blocked valid
signal and can be transmitted from the listening device to an external device, the wind-blocked
valid signal A microphone device for generating first and second microphone signals, and a first
device for filtering the first and second microphone signals branched into the first branch line to
obtain the first filtered signal Using a first filter signal from a first filter system having a latency,
and first and second microphone signals branched to a second branch parallel to the first branch
or a signal based thereon And a wind noise reduction device for obtaining a transmission signal
by reducing a wind component.
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[0010]
In the present invention, wind noise reduction is performed in a separate branch line (second
branch line) which is provided in parallel to the main signal processing branch line (first branch
line) of the listening apparatus and generates a transmission signal.
[0011]
In an embodiment, the second filter system wherein the parameters used to filter wind noise are
obtained by the first filter system and the defined signal for transmission has a shorter latency
than the first filter system Is optionally obtained by
And, since the wind noise reduction parameter is applied to the signal obtained by the short
latency time, the wind noise removed signal is provided for transmission after the shortened
latency time. The small time difference between the signal comprising the wind provided after
the second filter system and the parameters obtained through the first filter system is not really
important.
[0012]
Preferably, when filtering in the first filter system, the respective microphone signal is split into
more channels than in the second filter system. Such a large number of channels in the first filter
system makes it possible to detect wind more reliably and more accurately. For wind reduction
itself it is sufficient to split the signal into fewer channels.
[0013]
Application of the parameter to the second filtered signal may be performed by multiplying the
second filtered signal by a parameter dependent coefficient. In particular, if the parameter is an
amplification, it is desirable to multiply the parameter with the second filter signal.
[0014]
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In particular, each coefficient for multiplication can be determined by mean value assignment,
minimum value assignment or maximum value assignment. Basically, when more channels than
the second filter system are expected in the first filter system, it is necessary to assign multiple
channels to one channel each time. The resulting channels can then be assigned the mean value
of the input channel, the minimum value of the input channel or the maximum value of the input
channel. Depending on the choice of assignment, the degree of wind reduction can be influenced.
[0015]
In a development, both microphone signals can be filtered by the second filter system, with the
intermediate signal occurring first being combined with the second filter signal by the
beamforming device. This has the advantage that a correction signal is provided for the signal to
be transmitted.
[0016]
In the case of the listening device according to the invention, the first filter system comprises, on
average, a filter which is possibly longer than the second filter system. This long filter leads to a
clear separation of the channels and thus to a good detection of the wind, but with a long latency.
[0017]
Furthermore, the first filter system can have more channels at the output than the second filter
system. As the channels increase, higher frequency resolution can be achieved. While this is
advantageous for wind detection, it adds even more latency.
[0018]
In particular, the second filter system can have 2 to 10 channels at the output, and the first filter
system can have 16 or more channels at the output. In practice it is particularly advantageous if
the second filter system has, for example, four channels and the first filter system has sixteen or
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forty-eight channels. Thereby, on the one hand qualitatively high-value wind detection can be
achieved after the first filter system, and on the other hand qualitatively sufficient wind reduction
can be achieved after the second filter system.
[0019]
Thereby, it is very advantageous to be able to provide a binaural hearing aid system in which the
first hearing aid is formed to have the above-mentioned characteristics and the second
reinforcement is an external device. Thus, a wind-reduced signal can be transmitted from one
hearing aid to the other on the other side of the head with short latency.
[0020]
The features and effects described above in relation to the method according to the invention are
also applicable to the listening device according to the invention and vice versa.
[0021]
The invention will be explained in more detail on the basis of the attached figures.
[0022]
1 shows the basic structure of a hearing aid according to the prior art.
The output spectra for different wind strengths are shown.
FIG. 2 is a schematic block diagram of components for generating a transmission signal in a
listening device.
[0023]
The examples which will now be described in detail are advantageous embodiments of the
invention.
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[0024]
In many listening devices, the reduction of wind disturbances is very important.
The field of use is a headset, a binaural hearing aid, but in general the transmission from one ear
to the other is also a field of use.
[0025]
In particular, it is applied to wind noise suppression or wind noise reduction of both ears. At that
time, it is determined on which side of the body a larger wind noise disturbance signal is present.
A signal is transmitted from the weak wind side to the other side each time. This transmission
can be limited to frequencies below the critical frequency based on a typical wind spectrum (see
FIG. 2).
[0026]
However, it is advantageous if the wind disturbance is further reduced. For that purpose,
according to the first attempt, wind noise can be detected at the receiving end of the
transmission. As a precondition, it is necessary that two microphone signals of high quality be
provided after transmission so that the fine structure of the signal necessary for wind detection is
obtained. Therefore, high quality 2-channel transmission is required. However, this requires data
processing capacity for transmission, which is so high that it is expedient to reduce wind noise
already before transmission.
[0027]
According to another attempt, the frequency dependent or frequency independent wind intensity
or wind noise attenuation parameter is transmitted to the other hearing aid in order to reduce
the amplitude of the relevant frequency band (or generally the lower frequency band) can do.
However, for that purpose, additional data having a sufficiently high update rate must be
transmitted. This seems to be impossible in practice.
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[0028]
Based on these considerations it is concluded that it is desirable to reduce the wind disturbance
before transmitting to the other hearing aid in the case of binaural processing or before
transmitting to an external or additional device. This is particularly advantageous when the wind
disturbs both sides of the binaural system and not only mainly on one side of the binaural
system, but also during the alternation process when the windward side changes. It is. This case
is just the weak point of the system transmitting only the raw broadband signal.
[0029]
However, reducing wind noise prior to transmission creates problems with latency, ie, signal
delay. That is, on the one hand, wind noise should be detected reliably, which requires long filters
or multi-channel filter banks. Such wind analysis, including wind noise reduction, has a latency of
about 5-6 ms. On the other hand, the transmission of the signal itself likewise requires such a
time. Finally, processing on the receiving side of the transmitted signal is necessary, which for
example requires 5 ms as well. However, the latency has to be reduced since only up to 10-11 ms
are allowed for the whole transmission and processing. In the present invention, the reduction of
the waiting time is achieved by the parallel branch line 11 independently of the main processing
branch line 10 in which the signal to be transmitted with reduced wind (transmission signal)
generates an output signal of the sound of the listening device. It is achieved by being generated.
First of all, a transmission signal interrupted by wind from one or more microphones is supplied
to the parallel branch line 11. The reduction of the wind component of the transmission signal
disturbed by the wind takes place in the parallel branches 11 independently of the main
processing branch 10. Alternatively, wind reductions (devices) already present in the main
processing branch line 10 (hereinafter referred to as short branch line 10) are used for wind
reduction in the parallel branch lines 11. Thus, wind detection or analysis is performed at the
first branch line 10 and wind reduction is performed at the second branch line 11. This is shown
schematically in FIG. In the first branch 10, processing is performed on, for example, 16 or 48
channels, while processing in the second branch is performed on fewer channels, such as 1 or 4
channels. The data from the first branch line 10 is then used for wind noise removal in the
second branch line 11.
[0030]
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9
In principle, the second windline 11 with fewer channels can be used for wind intensity
detection, but the existing wind noise remover provided from a large number of channels (here
48) It is more desirable from the viewpoint of operation cost to use the value of and to convert
this number of channels into a channel with fewer second branch lines 11. Such a conversion is
less expensive and is a less complex conversion with average or maximum operation of the
corresponding channel with higher resolution of the first branch 10.
[0031]
The specific example of FIG. 3 shows the signal processing elements of the individual listening
devices which generate the signals to be transmitted. A casing incorporating the illustrated
elements is not shown here.
[0032]
The exemplary listening device comprises two microphones 12, 13 as input conversion devices.
The microphones 12, 13 sense ambient sounds including wind noise, for example. The
microphone produces an analog microphone signal from this ambient sound. The microphone
signals are supplied to analog / digital converters 14 and 15, respectively. In some cases, such
analog to digital conversion may be omitted. After digital conversion, the first microphone 12
produces a digital first microphone signal ms1 and the second microphone 13 produces a digital
second microphone signal ms2.
[0033]
At the first branch 10, the first microphone signal ms1 is supplied to the high resolution first
filter bank 16. On the other hand, in parallel, the second microphone signal ms2 is supplied to
the filter bank 17 that breaks up higher. Both filter banks 16, 17 divide the input signal here into
48 channels (possibly different numbers of channels). Both high resolution filter banks 16, 17
can be combined into a first filter system. This first filter system or filter bank 16, 17 supplies the
first filter signal fs1 with a first latency of, for example, 5 ms. In order to achieve high selectivity,
the latency is long, as the first filter system is high resolution and provides signals to a large
number of channels or the individual filters of the first filter system are relatively long. All first
filter signals fs1 of both microphone channels are supplied to a wind noise analysis unit 18, 22
comprising a wind noise evaluation unit 18 and a conversion device 22. By means of the wind
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noise analysis unit, wind noise is detected, for example, by correlation analysis. The amplification
is then calculated here for each of the 48 channels, so that a multichannel amplification signal v
is produced at the output. For example, amplification may be reduced when multiple wind noises
are present in a channel.
[0034]
The multi-channel amplified signal v and the first filter signal fs1 are usually further processed in
the listener in another way. This is not, however, shown in FIG. In particular, the multi-channel
amplified signal v is used to remove wind from the overall signal, ie the first filter signal fs1, and
to generate an appropriate output signal. However, preferably the generation of a transmission
signal for the transmission of radio is most important.
[0035]
In the second branch line 11, a broadband transmission signal u is generated. The transmitted
signal is freed of wind noise or at least reduced in wind noise. Furthermore, the second branch
line 11 has a shorter latency than the first branch line 10. In this case, the first microphone
signal ms1 and / or the second microphone signal ms2 are optionally supplied at the second
branch to the second filter system which supplies the second filter signal fs2 as a transmission
signal interrupted by wind. In the simplest case, not shown in FIG. 3, only the first microphone
signal ms1 or the second microphone signal ms2 is processed in the second branch 11 as a
transmission signal interrupted by wind. The optional second filter system consists of only
individual small filter banks (such as the filter bank 19 of FIG. 3). This filter bank divides the
signal, for example, into four channels. In this case, the signals in the channels show each other a
second filtered signal fs2.
[0036]
In the higher expanded version shown in FIG. 3, the first digital microphone signal ms1 is fed
here to the first filter bank 19 of 4 channels and the second digital microphone signal ms2 is fed
here to the second filter bank 20 of 4 channels Be done. Therefore, first, the intermediate signals
zs1 and zs2 are generated at the output side of the filter banks 19 and 20. This intermediate
signal is supplied to the beam forming device 21. The beamforming device forms from the
intermediate signal a second filtered signal fs2 which is present in parallel in the four channels.
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[0037]
The latency is shorter than the latency of the filter banks 16, 17 of the first branch 10, since the
filter banks 19, 20 divide the respective signals into fewer (here four) channels. In the case of the
filter banks 19, 20, the individual filters can be even shorter. Because a lower rise rate is
required. This also results in shorter waiting times. In this case, secondary sampling can be
omitted. Thus, filter banks 19, 20 can also be referred to as time domain filter banks.
[0038]
The amplification value v obtained for the 48 channels in the first branch line 10 is applied in
this example to the second filter signal fs2 present in the four channels obtained with a shorter
waiting time. For this purpose, it is necessary to convert the amplified values v of 48 channels
into 4 channels by the converter 22. This conversion is performed with four parameters fp. In the
multiplier 23, the second filter signal fs2 is multiplied by the parameter fp belonging thereto in
each channel. Because of the longer latency of the first branch line 10, the parameter fp is
derived from the wind that is present before the time of the generation of the second filter signal
fs2. However, this is not important for wind noise.
[0039]
The second filter signal fs2 with the parameter fp is supplied to the synthesis filter bank, in the
simplest case the adder 24. The adder determines a wideband transmission signal u from the
second filtered signal. The transmitting device 25 receives the transmission signal for
transmitting the transmission signal to an external device, in particular to another hearing aid,
wirelessly or by wire. The converter 22 converts, for example, the first two channels of the 48
input channels into the first channels of the four output channels. In addition, the next four input
channels of the 48 input channels are converted to the second of the four output channels. This
is done sequentially. Thus, for example, non-uniform transformations take into account typical
wind spectra (see FIG. 2).
[0040]
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12
That is, in the above embodiment as is general in the present invention, it is advantageous if the
wind is reduced in the signal generated from the at least two microphone signals before being
transmitted to the other hearing aid or additional equipment. It is. In that case, additional delay
or latency is avoided by using a low delay filter bank or filter bank system in parallel to the multichannel filter bank for normal processing for signal transmission. Ru. Furthermore, the already
existing multi-channel wind noise estimation (and its amplification) is used for conversion to
smaller filter banks or smaller filter bank systems (which can also be used for directional
microphones) This can save additional computational costs.
[0041]
16, 17 ... filter system fs1, fs2 ... filter signal ms1, ms2 ... microphone signal u ... transmission
signal
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