CN102638740B - Difference double-microphone noise reducing method for breathing mask - Google Patents

Abstract

The invention relates to a difference double-microphone noise reducing method for a breathing mask. The method comprises the following steps in turn: connecting two same single microphones in a difference connecting manner; deducing a relation of a distance between the two single microphones and a difference of phase angles of two-way audio signals output by the microphones; giving a critical value of the difference of the phase angles; determining a main frequency range needing the breathing mask to perform noise suppression; deducing the distance between the two single microphones; coaxially, symmetrically and equidistantly mounting the two single microphones on two sides of the inner cavity wall of the breathing mask by taking a point acoustic source in the cavity as a center, wherein the distance between the two single microphones is the deduced distance; and returning to the second step and adjusting the distance between the two single microphones when the to-be-suppressed noise frequency range of the breathing mask is changed. According to the method provided by the invention, the noise suppression capacity is greatly increased; the microphone jetting phenomenon is obviously eliminated; the existing single microphones are replaced by the double microphone in difference connection; the structure change is slight; and the original oxygen supply protecting property is maintained.

Description

The difference diamylose gram noise-reduction method of breathing mask

Technical field

The present invention relates to breathing mask field, especially a kind of difference diamylose gram noise-reduction method of breathing mask.

Background technology

In the field such as aviation and fire-fighting, breathing mask is mainly the user such as pilot and fireman and operationally provides filtration oxygen supply, and be the individual protection harness of user's key, breathing mask is provided with Mike, can be the user such as pilot and fireman and uses when conversing.

The Mike that existing breathing mask is installed is single Mike, and under the environment for use condition of very noisy, single Mike is while the pickup user signal that speak in front in face shield body cavity, and the ambient noise signals such as very noisy are come in by mask body is also picked.So just make the ambient noise signal mixing such as user's signal that speak in front in face shield body cavity and very noisy, the sound quality causing single Mike to pick up is deteriorated.In addition, single Mike is in the process used, and because it is with the lip of very near distance forward in the face of user, the air-flow that user speaks can directly be sprayed onto on single Mike, and comparatively serious spray wheat phenomenon will occur.Visible, above-mentioned two kinds of phenomenons all seriously can affect the speech quality of user.

Summary of the invention

The object of the present invention is to provide a kind of can effectively filtering very noisy interference, the difference diamylose gram noise-reduction method eliminating spray wheat phenomenon, greatly improve the breathing mask of speech quality.

For achieving the above object, present invention employs following technical scheme: a kind of difference diamylose gram noise-reduction method of breathing mask, the method comprises the step of following order:

(1) two identical single Mikes are connected with difference connected mode, composition diamylose gram noise reduction unit, derive the relational expression of the difference at distance between two single Mikes and its output two-way audio signal phase angle, analyze the superposition of two-way audio signal, provide the critical value of the difference at phase angle; Two described single Mikes are moving-coil Mike;

(2) analyze the main frequency part of the background very noisy in breathing mask institute applied environment, determine to need breathing mask to carry out the main frequency range of noise suppressed;

(3) be in critical value in the difference at two-way audio signal phase angle, and in the noise frequency range suppressed needed for breathing mask, derive the distance between two single Mikes, by two single Mikes equidistant both sides being arranged on breathing mask internal chamber wall of coaxial-symmetrical centered by point sound source in chamber, the distance between two single Mikes is the above-mentioned distance derived;

(4) when the noise frequency range suppressed needed for breathing mask changes, return step (2), adjust the distance between two single Mikes.

As shown from the above technical solution, when the breathing mask that user puts in the present invention is spoken, the air-flow that user speaks no longer directly is sprayed onto on single Mike that two symmetries are arranged on breathing mask internal chamber wall, avoids spray wheat phenomenon; Two single Mikes adopt differential mode to connect, output difference sub-signal, can carry out noise suppressed well in subsequent transmission process.In a word, present invention greatly enhances noise inhibiting ability, obviously eliminate spray wheat phenomenon, only existing single Mike is replaced with the diamylose gram that difference connects, structural change is little, and maintains original oxygen supply barrier propterty.

Accompanying drawing explanation

Fig. 1,2 is respectively the principle of noise reduction figure that the present invention adopts direct differential connected mode, indirectly difference connected mode;

Fig. 3,6 is respectively noise reduction vector analysis figure of the present invention and noise-reduction method flow chart;

Fig. 4,5 is noise reduction analysis chart of the present invention.

Embodiment

A kind of difference diamylose gram noise-reduction method of breathing mask, the method comprises the step of following order: two identical single Mikes connect with difference connected mode by (1), composition diamylose gram noise reduction unit, derive the relational expression of the difference at distance between two single Mikes and its output two-way audio signal phase angle, analyze the superposition of two-way audio signal, provide the critical value of the difference at phase angle; (2) analyze the main frequency part of the background very noisy 4 in breathing mask institute applied environment, determine to need breathing mask to carry out the main frequency range of noise suppressed; (3) be in critical value in the difference at two-way audio signal phase angle, and in the noise frequency range suppressed needed for breathing mask, derive the distance between two single Mikes, by two single Mikes equidistant both sides being arranged on breathing mask internal chamber wall of coaxial-symmetrical centered by point sound source 3 in chamber, the distance between two single Mikes is the above-mentioned distance derived; (4) when the noise frequency range suppressed needed for breathing mask changes, return step (2), adjust the distance between two single Mikes.As shown in Figure 6.

As shown in Figure 1, 2, two described single Mikes are first and second single Mike 1,2, and first and second single Mike 1,2 all fits tightly on the internal chamber wall of breathing mask.Two described single Mikes are moving-coil Mike, first and second single Mike 1,2 difference connects and distributes along both center line A-A bilateral symmetry, point sound source 3 is user's voice, point sound source 3 to be positioned on center line A-A and with first and second single Mike 1,2 coaxial, the air-flow avoiding user's voice is directly sprayed onto on microphone, effectively prevent spray wheat phenomenon, and point sound source 3 is with non-direction spherical wave overseas publicity.First and second single Mike 1,2 is directive property Mike, is realized the pickup of the sound wave to point sound source 3 by the forced vibration of its respective vibrating diaphragm.

As shown in Figure 1, described difference connected mode adopts direct differential connected mode, and described direct differential connected mode is with point sound source 3 as a reference, and the audio signal of two single Mikes exports in-phase end head and the tail and directly to connect difference output.When there is very noisy 4 in breathing mask surrounding environment, for the breathing mask adopting direct differential connected mode, the phase angle difference of the low frequency signal in the very noisy 4 that two single Mikes pick up is less than or equal to 60 °, low frequency signal in very noisy 4 can be suppressed well, and the high-frequency signal part in very noisy 4 effectively can be suppressed by the cover body of breathing mask.

As shown in Figure 2, described difference connected mode adopts indirect difference connected mode, and described indirect difference connected mode is with point sound source 3 as a reference, and the audio signal of two single Mikes exports in-phase end successively through difference channel 5, filter network 6 difference output.For the breathing mask adopting indirect difference connected mode, filter network 6 and difference channel 5 effectively can suppress the high-frequency signal in very noisy 4.

As shown in Figure 3, there is the difference at phase angle in the pickup of two identical single Mikes to same point sound source 3 signal on coaxial based on the distribution of certain distance coaxial-symmetrical, and the principle that the difference at the phase angle of different frequency signals part is not identical, the difference φ at phase angle of the two-way audio signal exported after deriving the frequency f of point sound source 3 signal, two single Mike's pickup point sound source 3 signals, the relational expression of the spacing L of two single Mikes are as follows:

According to the principle that the available polar plot of the superposition of audio signal represents, make the vector analysis figure of the superposition of two-way audio signal, show that φ absolute value exists critical value that is: φ absolute value exists within time, mould after the superposition of two-way audio signal is long, and to be less than or equal to the mould of its single audio signal long, and φ absolute value is exceeding time, the mould of the superposition calculation value of two-way audio signal is grown up long in the mould of single audio signal.

By the critical value of formula (1) and φ absolute value derive be in two-way output audio signal in noise suppressed frequency range needed for breathing mask φ in its critical value within time, the distance L between two single Mikes.

Below in conjunction with Fig. 3,4,5,6 the present invention is further illustrated.

Single Mike all can represent with sinusoidal class signal the signal of telecommunication of the acoustic signals institute output audio such as user's voice and chamber external environment very noisy 4 in the chamber of picking up, and can express with the vector expression of sinusoidal class signal, and expression is as follows:

Point sound source 3 is user's voice in chamber, and its coverlet Mike picks up and the sinusoidal class signal of the signal of telecommunication of output audio is reduced to:

And this is represented with vector, expression formula is:

Very noisy 4 is chamber external environment very noisy, and coverlet Mike picks up and the sinusoidal class signal of the signal of telecommunication of output audio is reduced to: and this is represented with vector, expression formula is:

When calculating two single Mikes one by one and picking up the two paths of signals superposition of arriving to point sound source 3 and very noisy 4, the vector expression of all available two sinusoidal class signals with represent the value that two single Mikes pick up, right with superposition calculation, can express with vector analysis figure, as shown in Figure 3.

As shown in Figure 3, mould appearance etc., have the difference φ at phase angle between the two.When the absolute value of φ is less than or equal to 60 °, with difference mould long to be less than or equal to with mould long; When with between the absolute value of difference φ at phase angle when being greater than 60 °, with difference mould grow up in mould long; When with between the absolute value of difference φ at phase angle when equaling 180 °, with difference mould long to equal with the long sum of mould.

Namely when first and second single Mike 1,2 pick up the difference φ at the phase angle of signal absolute value be less than or equal to 60 ° time, the mould that the differential signal that diamylose gram noise reduction unit exports is less than or equal to the signal picked up with a single Mike is long, realizes the suppression to signal; When first and second single Mike 1,2 pick up the difference φ at the phase angle of signal absolute value be greater than 60 ° time, the differential signal that diamylose gram noise reduction unit exports is greater than with the mould of the signal of single Mike's pickup long, especially when the absolute value of the difference φ at phase angle equals 180 °, the differential signal that diamylose gram noise reduction unit exports equals long with the twice mould of the signal of single Mike's pickup, realizes the enhancing to signal.

Thus need to make the difference φ absolute value of diamylose gram noise reduction unit to the signal phase angle that point sound source 3 picks up equal 180 °, and then diamylose gram noise reduction unit effectively strengthens point sound source 3; Make the difference φ absolute value of diamylose gram noise reduction list to the signal phase angle that very noisy outside chamber 4 picks up be less than or equal to 60 °, and then diamylose gram noise reduction unit effectively suppresses to very noisy outside chamber 4, its mathematical theory basis is derived as follows:

The gain G of diamylose gram noise reduction unit is expressed as its pickup processing effect to acoustic signals, and mathematic(al) representation is:

$G=10\lg \left(\frac{\left|\right|{\stackrel{\·}{x}}_{01}\left|\right|}{\left|\right|{\stackrel{\·}{x}}_{02}\left|\right|}\right)=10\lg (2*|\sin \frac{\mathrm{\φ}}{2}\left|\right),$

When | φ | when≤60 °, $0\≤\sin \frac{\mathrm{\φ}}{2}\≤\frac{1}{2},$ $-\∞\≤\lg (2*\sin \frac{\mathrm{\φ}}{2})\≤0,$ -∞≤G≤0；

As 60 ° of < φ <300 °, 0<G≤3.

Thus known as | φ | when≤60 °, the gain G of the acoustic signals of diamylose gram noise reduction unit pickup is less than or equal to 0, has inhibitory action to acoustic signals; When the value of φ is between 60 ° and 300 °, there is humidification 0<G≤3 to acoustic signals.

As can be seen here, the realization key of diamylose gram noise-reduction method is that diamylose gram noise reduction unit meets the difference at the phase angle of 4 pickoff signals of very noisy outside chamber | φ | and≤60 °, and this key is the distance L between Reasonable adjustment two single Mikes, diamylose gram noise reduction unit is met the difference at the phase angle of the low frequency signal institute pickoff signals in very noisy outside chamber 4 | φ |≤60 °, its mathematical theory is derived as follows:

When only considering that the sound wave independent role of point sound source 3 is on first and second single Mike 1,2, as shown in Figure 1, because of first and second single Mike 1,2 be symmetrically distributed in point sound source 3 both sides and distance very near, assert that the signal of point sound source 3 is not decayed, the difference φ at the phase angle of the signal that first and second single Mike 1,2 picks up equals π, what namely first and second single Mike 1,2 picked up is exactly equivalent, anti-phase signal, thus diamylose gram noise reduction unit output difference sub-signal, its amplitude size is the twice of single Mike's signal, namely realizes the postiive gain G of the 3dB of point sound source 3 signal ₀₀.

When very noisy 4 is positioned at the left side of the coaxial line of diamylose gram noise reduction unit, as shown in Figure 1, the spacing of first and second single Mike 1,2 is near, assert the not decay between two single Mikes of very noisy 4 signal, the mould of the signal of two single Mike's pickups is equal, only there is the difference φ at phase angle.

The pass existed for the wavelength X of given φ value, distance L and signal is: according to sound frequency f and the computing formula between wavelength X and velocity of sound v $f=\frac{v}{\mathrm{\&lambda;}},$ : $f=\frac{2\mathrm{\&pi;v}}{(\mathrm{\&phi;}+2\mathrm{n\&pi;})L}.$

By formula known, n value is larger, and the complete waveform of the acoustic signals passed through in distance L is more, and namely the frequency of acoustic signals is larger; And for high-frequency signal, the face shield physical efficiency of breathing mask effectively intercepts, and very noisy 4 is mainly made up of low frequency signal, therefore gets n=0, $L=\frac{\mathrm{\&phi;\&lambda;}}{2\mathrm{\&pi;}},f=\frac{\mathrm{\&phi;v}}{2\mathrm{\&pi;L}}.$

As n=0, frequency gain known φ mono-timing, f and L is inversely proportional to, thus | and φ | when≤60 °, diamylose gram noise reduction unit is to chamber external environment very noisy 4 inhibitory action, and L is less, and blanketing frequency f is larger in institute, and the relational expression of its gain G and frequency is: and very noisy 4 signal primarily of low frequency signal mixing and composition and most of signal concentrates on below 500Hz, and the lip of speaker has one fixed width in chamber, therefore first get L=6cm to analyze, G=10lg (2sin (1.1088*10 can be drawn ^-3f)), Reduction Analysis Fig. 4 can be made.

Fig. 4 is analyzed known, when getting φ=180 °: therefore during L=6cm, $f=\frac{v}{2L}=\frac{34000}{2*6}=2833.3=2.8333\mathrm{KHz},$ Gain $G=10\lg (2*\sin \frac{\mathrm{\&phi;}}{2})=10\lg 2=3\mathrm{dB}.$ And as shown in Figure 1, during φ=180 °, what first and second single Mike 1,2 picked up is exactly equivalent, anti-phase signal.

When getting φ=60 °: therefore during L=6cm, $f=\frac{v}{6L}=\frac{34000}{6*6}=944.4=0.9444\mathrm{KHz},$ Gain $G=10\lg (2*\sin \frac{\mathrm{\&phi;}}{2})=10\lg 1=0\mathrm{dB}.$ And as shown in Figure 1, during φ=60 °, the modulus of the signal that first and second single Mike 1,2 picks up is equal.

When getting φ=300 °: therefore during L=6cm, $f=\frac{5v}{6L}=\frac{5*34000}{6*6}=4722=4.722\mathrm{KHz},$ Gain $G=10\lg (2*\sin \frac{\mathrm{\&phi;}}{2})=10\lg 1=0\mathrm{dB}.$ And as shown in Figure 1, during φ=300 °, the modulus of the signal that first and second single Mike 1,2 picks up is equal.

Analyze known, during L=6cm, the low frequency signal that diamylose gram noise reduction unit suppresses can reach 0.9444KHz, and the low frequency signal part met in very noisy 4 signal mainly concentrates on the demand of 500Hz.To different noise reduction demands, formula frequency can be passed through and gain carry out distance L reasonable in design, to reach best noise suppression effect.

As shown in Figure 5, time equally for L=6cm, when the frequency of very noisy 4 signal is at 0.9444KHz, the gain of diamylose gram noise reduction unit pickup noise is 0dB, relative G ₀₀for 0dB-3dB=-3dB; When the frequency of very noisy 4 signal is at 4.722KHz, the gain of diamylose gram noise reduction unit pickup noise is 0dB, relative G ₀₀for-3dB-3dB=-6dB; When the frequency of very noisy 4 signal is at 2.8333KHz, the gain of diamylose gram noise reduction unit pickup noise is maximum, is 3dB, relative G ₀₀for 3dB-3dB=0dB.Visible in all frequency range of voice, the poorest noise reduction also has 0dB, sees the frequency response figure of very noisy 4 signal relative to sound-source signal in chamber of diamylose gram noise reduction unit pickup.

In a word, the present invention effectively can suppress the low frequency signal existed main in environment very noisy 4; The frequency range suppressed for the less high-frequency signal part that distributes in environment very noisy 4 is periodic distribution, and maximum gain is 0dB compared with the gain of sound wave of speaking in chamber, and is deadened can be suppressed well by mask body.

Claims (6)

1. a difference diamylose gram noise-reduction method for breathing mask, the method comprises the step of following order:

(1) two identical single Mikes are connected with difference connected mode, composition diamylose gram noise reduction unit, derive the relational expression of the difference at distance between two single Mikes and its output two-way audio signal phase angle, analyze the superposition of two-way audio signal, provide the critical value of the difference at phase angle; Two described single Mikes are moving-coil Mike;

(2) analyze the main frequency part of the background very noisy in breathing mask institute applied environment, determine to need breathing mask to carry out the main frequency range of noise suppressed;

(3) be in critical value in the difference at two-way audio signal phase angle, and in the noise frequency range suppressed needed for breathing mask, derive the distance between two single Mikes, by two single Mikes equidistant both sides being arranged on breathing mask internal chamber wall of coaxial-symmetrical centered by point sound source in chamber, the distance between two single Mikes is the above-mentioned distance derived;

(4) when the noise frequency range suppressed needed for breathing mask changes, return step (2), adjust the distance between two single Mikes.

2. the difference diamylose gram noise-reduction method of breathing mask according to claim 1, is characterized in that: described point sound source is the voice of user, two described single Mikes fit tightly on the internal chamber wall of breathing mask.

3. the difference diamylose gram noise-reduction method of breathing mask according to claim 1, it is characterized in that: described difference connected mode adopts direct differential connected mode, described direct differential connected mode is with point sound source as a reference, and the audio signal of two single Mikes exports in-phase end head and the tail and directly to connect difference output.

4. the difference diamylose gram noise-reduction method of breathing mask according to claim 1, it is characterized in that: described difference connected mode adopts indirect difference connected mode, described indirect difference connected mode is with point sound source as a reference, and the audio signal of two single Mikes exports in-phase end successively through difference channel, filter network difference output.

5. the difference diamylose gram noise-reduction method of breathing mask according to claim 1, it is characterized in that: the pickup of two identical single Mikes to the same point sound source signal on coaxial based on the distribution of certain distance coaxial-symmetrical exists the difference at phase angle, and the principle that the difference at the phase angle of different frequency signals part is not identical, the difference φ at phase angle of the two-way audio signal exported after deriving the frequency f of point sound source signal, two single Mike's pickup point sound-source signals, the relational expression of the spacing L of two single Mikes are as follows:

$f=\frac{2\mathrm{\&pi;v}}{(\mathrm{\&phi;}+2\mathrm{n\&pi;})L}$ ( $L=\frac{\mathrm{\&phi;\&lambda;}}{2\mathrm{\&pi;}}+\mathrm{n\&lambda;}(n=\mathrm{0,1,2}...N),$ V is velocity of sound) formula (1);

According to the principle that the available polar plot of the superposition of audio signal represents, make the vector analysis figure of the superposition of two-way audio signal, show that φ absolute value exists critical value that is: φ absolute value exists within time, mould after the superposition of two-way audio signal is long, and to be less than or equal to the mould of its single audio signal long, and φ absolute value is exceeding time, the mould of the superposition calculation value of two-way audio signal is grown up long in the mould of single audio signal.

6. the difference diamylose gram noise-reduction method of breathing mask according to claim 5, is characterized in that: by the critical value of formula (1) and φ absolute value derive be in two-way output audio signal in noise suppressed frequency range needed for breathing mask φ in its critical value within time, the distance L between two single Mikes.