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JP2000270391

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DESCRIPTION JP2000270391
[0001]
FIELD OF THE INVENTION This invention relates primarily to hearing aids.
[0002]
2. Description of the Related Art Although external noise is one of the factors that reduce the
intelligibility of hearing aids, in conventional hearing aids, the input / output characteristics and
frequency characteristics of the deafness ear are compensated by the characteristics of the
hearing aid, and signal-to-noise ratio It is mainstream to try to prevent further deterioration.
Although some amplifiers suppress the noise by dividing the amplifier into frequency bands and
controlling the amplification of the noise band, it is a problem when overlapping with the signal
band. In this case, although the noise can be reduced by the directivity of the microphone and
the array, since the scale of the device is limited with respect to the wavelength, the sharpness of
the directivity is not sufficient.
[0003]
SUMMARY OF THE INVENTION When it is intended to remove extraneous noise that degrades
the intelligibility of a hearing aid by the directional characteristics of the microphone, the
conventional method obtains sharp directional characteristics because of limitations on the size
of the microphone array. I can not. The present invention significantly improves this directivity.
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[0004]
SUMMARY OF THE INVENTION A receiver array comprising microphones of multiple channels is
placed on the frame of a spectacles-type fitting or on the support beam of a headphone-type
fitting. The output of each microphone is subjected to Fourier transform to obtain an amplitude
spectrum and a phase spectrum, and the following operation is performed for each frequency
band. The phase difference between each channel is multiplied by an arbitrary coefficient to
enlarge the difference, and further, the amplitude and phase between each channel are
interpolated to calculate the interpolated channel output, and the number of channels including
the interpolated channel is made to any size Multiply. These outputs are multiplied by an
arbitrary weight function to perform phasing addition (simply adding in the case of creating a
beam in the front direction), and inverse Fourier transform to form a conventional amplifier
input.
[0005]
DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a system diagram showing an
embodiment of the present invention. 1, 2, 3, and 4 M1, M2, Mi, and Mm (i = 1, 2,... M) are mchannel microphones at horizontal distance intervals that are the frame of the spectacles-type
mounting tool or the support beam of headphones Arranged to form 5 microphone arrays.
[0006]
fi (t) (i = 1, 2,..., m) is the output of each microphone, and is converted to the frequency spectrum
Fi (ω) (i = 1, 2,..., m) of m channels by 6 Fourier transformers Be done. 7, 8, 9 and 10 Ai (ω) (i =
1, 2,..., M) and αi (ω) (i = 1, 2,... M) respectively represent Fi (ω) (i = 1, 1) 2, ..., m) amplitude
spectrum and phase spectrum. Here, ω is an angular frequency. The following operations are
performed on these outputs at 11 for each frequency band. The phase difference between the
channels is determined from αi (ω) (i = 1, 2,..., m), and this difference is multiplied by an
arbitrary coefficient Kp to expand the phase difference between the channels, and a new phase
spectrum βi ( ω) (i = 1, 2,..., m) is obtained. The frequency spectrum becomes Gi (ω) (i = 1, 2,...,
M), and the amplitude spectrum Ai (ω) (i = 1, 2,..., M) and the phase spectrum become 12, 13, 14
and 15. It shows β i (ω) (i = 1, 2,..., m). Next, for each frequency band, the amplitude and phase
between each channel can be set arbitrarily from Ai (ω) (i = 1,2, ..., m) and βi (ω) (i = 1,2, ... m)
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in 16 To calculate the spectrum of the interpolation channel, multiply the number of channels
including the interpolation channel to an arbitrary size n = K cm, and calculate a new frequency
spectrum H k (ω) (k = 1, 2, ..., n). 17, 18, 19 and 20 show its amplitude spectrum Bk (ω) (k = 1,
2,..., N) and phase spectrum γk (ω) (k = 1, 2,... N). Next, at 21, shaping is performed by
multiplying the amplitude Bk (ω) (k = 1, 2,..., N) of each channel by an arbitrary weighting
function Wk (k = 1, 2,. The frequency spectrum J k (ω) (k = 1, 2,..., N) is obtained. 22, 23, 24 and
25 show the amplitude spectrum C k (ω) (k = 1, 2,..., N) and the phase spectrum γ k (ω) (k = 1,
2,..., N). At 26, these inputs are subjected to phasing addition in any direction (simply adding
when forming a beam in the front direction) to obtain a directional output J (ω). At 27, J (ω) is
subjected to inverse Fourier transform to form a directional output j (t), which is used as a
conventional amplifier input.
[0007]
An example calculation is shown below for the case of a linear array. The array length is al, the
microphone spacing is d, the number of microphone channels is m, the sound wave arrival
direction is measured from the front of the array θ, the phase difference expansion coefficient is
Kp, the channel multiplication coefficient is Kc, and the wavelength is λ. From the above, the
microphone spacing d is d = al / (m−1), the number of multiplication channels n is n = K cm, and
the multiplication channel spacing s is s = al · Kp / (n−1). The phase spectrum βi (ω) is given by
equation (1). When the phasing azimuth is 0 degree, the directivity characteristic R (θ) of the
addition output is as follows according to each condition. 1. In the case of a nondirectional
microphone R (θ) = R (θ). 2. In the case of a unidirectional microphone R (.theta.) = R (.theta.)
CR (.theta.) C = R (.theta.) O (1 + cos (.theta.)) / 2 (3) In the case of a 3.2 second order sound
pressure gradient microphone R (θ) = R (θ) g where a is the distance between the sound
pressure gradient microphones. 4 When Shading is not Performed In the case of Wk = 1, R (θ) o
in the equations (2), (3) and (4) is the equation (5).
[0008]
The calculation results of the directivity characteristic are shown in FIG. 2, 3 and 4 show the case
where the phase difference expansion coefficient Kp = 1 and the channel multiplication
coefficient Kc = 1, respectively, using an omnidirectional element, a unidirectional element and a
secondary sound pressure gradient element. There is. On the other hand, in FIG. 5, FIG. 6 and
FIG. 7, the pointing width is reduced with Kp = 5 and Kc = 5. With respect to the improvement of
the pointing width, in FIGS. 8, 9 and 10, the shading is further added to attenuate the side lobes.
However, since the pointing width is slightly increased by this, in FIGS. 11, 12 and 13, the
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pointing width is reduced again as Kp = 8 and Kc = 8. Here, the array length al = 15 cm, the
number of microphone channels m = 2, the frequency f = 1000 Hz, the wavelength λ = 34 cm,
and the inter-sensor distance a = 5 cm of the secondary sound pressure gradient element. In
addition, the shaping coefficient Wk is 0.54 + 0.46 cos (π (2k−n−1) / (n−1)). Comparing "Fig.
2, 3 and 4" with "Fig. 5, 6 and 7" and "Fig. 8, 9 and 10" with "Fig. 11, 12 and 13", Kp and Kc are
obtained. It can be seen that the pointing width is significantly reduced by increasing. In the case
where the microphones can be arranged in the vertical direction as in the headphone type
wearing tool, it is possible to further improve the directivity characteristic in the vertical
direction as well.
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