CN104853279A - Directional sound generating apparatus and method - Google Patents
Directional sound generating apparatus and method Download PDFInfo
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- CN104853279A CN104853279A CN201510309689.0A CN201510309689A CN104853279A CN 104853279 A CN104853279 A CN 104853279A CN 201510309689 A CN201510309689 A CN 201510309689A CN 104853279 A CN104853279 A CN 104853279A
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Abstract
The invention provides a directional sound generating apparatus and method. The apparatus comprises: a signal preprocessing module for successively performing bandpass filtering, gain amplifying, low-frequency compensating and compression amplitude limiting processing on input digital audio signals and sending the processed signals to a pulse-width modulation module; the pulse-width modulation module for obtaining modulated ultrasonic carrier wave signals from the processed signals by use of pulse-width modulation; a driving amplification module for performing driving amplification on the modulated ultrasonic carrier wave signals; an ultrasonic transducer array module for matching the amplified modulated ultrasonic carrier wave signals with an ultrasonic sensor array through an LC low-pass filtering circuit to emit ultrasonic signals and generating directional sound by use of nonlinear propagation of the ultrasonic signals in air, wherein the ultrasonic sensor array in an ultrasonic energy transducer comprises multiple array elements, and the carrier wave frequency of the ultrasonic carrier wave signals are arranged according to the work frequency of each array element. The pulse-width modulation structure is quite simple, the distortion is quite small, and the integration and the energy efficiency ratio are good.
Description
Technical field
The present invention relates to directed audio technology field, particularly the directed sound generation device of one and method.
Background technology
Directed audio technology is a kind of by the technology of sound wave controlled interior orientation transmission in a certain region in space, propagate different from the sound wave that conventional loudspeakers sends to all directions, directed audio technology can only propagate sound in a particular area, then decay outside specific region very fast, almost can't hear sound, therefore there is good privacy, decrease the generation of noise, all gather around at military and civil area and have wide practical use.
Have carried out some research for directed audio technology both at home and abroad, its Main Basis is that two kinds of parameter acoustic arrays of Westervelt equation and Berktay Far field solution are theoretical, utilizes the ultrasonic nonlinear interaction propagated in atmosphere to produce the sub-audible sound of direction propagation.Wherein signal transacting and modulator approach are the key technologies producing directed sound.
The equal more complicated of technology of the directed sound of current generation, and cost is very high, is generally applied in military field, almost not having in civil applications.
Therefore, those skilled in the art need to provide a kind of directed sound generation device, can reduce costs, and make directed audio technology and products application at civil area.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of directed sound generation device and method, can reduce costs, and makes directed audio technology and products application at civil area.
The embodiment of the present invention provides a kind of directed sound generation device, comprising: signal pre-processing module, Pulse width modulation module, drive amplification module and ultrasound transducer array module;
Described signal pre-processing module, for carrying out bandpass filtering, gain amplification, low-frequency compensation and compression amplitude limiting processing successively to the digital audio and video signals of input, sends to described Pulse width modulation module by the signal after process;
Described Pulse width modulation module, for utilizing pulse width modulation to obtain modulated ultrasonic carrier signal the signal after described process;
Described drive amplification module, for carrying out drive amplification to described modulated ultrasonic carrier signal;
Described ultrasound transducer array module, for the modulated ultrasonic carrier signal after amplification is launched ultrasonic signal by LC low-pass filter circuit coupling ultrasonic sensor array, utilizes the aerial nonlinear propagation of ultrasonic signal to produce direct sound; Ultrasonic sensor array in described ultrasonic transducer comprises multiple array element, and the carrier frequency of described ultrasonic carrier signal is arranged according to the operating frequency of each described array element.
Preferably, described Pulse width modulation module carries out pulse width modulation according to following pulse width modulation transfer function and obtains described modulated ultrasonic carrier signal:
S
o＝H
PWM{S
t}；
Wherein, S
ofor modulated ultrasonic carrier signal; S
tfor the digital audio and video signals of input; H
pWMfor pulse width modulation transfer function;
The frequency of described ultrasonic carrier signal is f
c; f
c=f
t-f
e;
Wherein, f
tfor the center operating frequency of array element in described ultrasound transducer array, f
efor the error compensation factor, f
e∈ [-100,0) ∪ (0,100].
Preferably, the center operating frequency f of array element in described ultrasound transducer array
tmeet the following conditions: 3f
sig≤ f
t≤ f
mos;
Wherein, f
sigfor the peak frequency of described digital audio and video signals, f
mosfor the peak frequency of described Pulse width modulation module breaker in middle device.
Preferably, the unloaded duty ratio of described pulse width modulation is 50% ± 10%.
Preferably, the phase difference of any two array elements in described ultrasound transducer array is less than 90 degree.
Preferably, described signal pre-processing module, also for when described digital audio and video signals being detected for zero load, transmit control signal to described Pulse width modulation module, described Pulse width modulation module is closed.
Preferably, the cut-off frequency of described band pass filter and pass band width are determined by the bandwidth of the bandwidth sum ultrasonic transducer of described digital audio and video signals.
Preferably, the formation of the ultrasonic sensor array of described ultrasound transducer array is the staggered or hexagon weighting array of rectangle.
Preferably, the array element in the staggered or hexagon weighting array of described rectangle adopts and is connected in parallel, and center distance d between any two adjacent array elements is equal, and d meets following condition:
Wherein, r is the vibrating diaphragm radius of array element, f
cfor the frequency of ultrasonic carrier signal, c is ultrasonic transducer propagation velocity in media as well.
Preferably, the electric capacity in described LC low-pass filter circuit is provided by the equivalent capacity of sonac array element in described ultrasound transducer array, and the inductance L e in described LC low-pass filter circuit meets the following conditions:
Wherein f
cfor the frequency of ultrasonic carrier signal, C is the direct capacitance of array element in described ultrasound transducer array, and n is the quantity of array element in described ultrasound transducer array.
The embodiment of the present invention also provides a kind of directed sound production method, comprises the following steps:
Bandpass filtering, gain amplification, low-frequency compensation and compression amplitude limiting processing are carried out successively to the digital audio and video signals of input;
Pulse width modulation is utilized to obtain modulated ultrasonic carrier signal the signal after described process;
Drive amplification is carried out to described brewed ultrasonic carrier signal;
Utilize LC low-pass filter circuit coupling ultrasonic sensor array to launch ultrasonic signal the brewed ultrasonic carrier signal after amplifying, utilize the aerial nonlinear propagation of ultrasonic signal to produce direct sound.
Preferably, describedly utilize pulse width modulation to obtain modulated ultrasonic carrier signal, specifically utilize following pulse width modulation transfer function to carry out:
S
o＝H
PWM{S
t}；
Wherein, S
ofor modulated ultrasonic carrier signal; S
tfor the digital audio and video signals of input; H
pWMfor pulse width modulation transfer function;
The frequency of described ultrasonic carrier signal is f
c; f
c=f
t-f
e;
Wherein, f
tfor the center operating frequency of array element in described ultrasound transducer array, f
tbe greater than 20kHz; f
efor the error compensation factor, f
e∈ [-100,0) ∪ (0,100].
Compared with prior art, the present invention has the following advantages:
The directed sound generation device that the present embodiment provides, utilizes Pulse width modulation module that the modulation of ultrasonic carrier signal digital audio and video signals is generated modulated ultrasonic carrier signal.The problem of and ultrasonic aerial low-frequency effect difference less in order to the signal amplitude solving pulse width modulation, has carried out preliminary treatment in front end to signal in the present invention, has comprised and carry out filtering, gain amplification, low-frequency compensation and compression amplitude limiting processing to signal.Because pulse width modulation is relatively simple for structure, distortion is less, and has good integration and Energy Efficiency Ratio, therefore, this device provided by the invention can be applied in civil area, such as, the sales counter ATM of bank can be applied in, the occasions such as the window of hospital, the explanation platform in museum.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
Fig. 1 is directed sound generation device embodiment one schematic diagram provided by the invention;
Fig. 2 is signal pre-processing module internal structure schematic diagram provided by the invention;
Fig. 3 is directed sound production method embodiment one flow chart provided by the invention.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.
For enabling above-mentioned purpose of the present invention, feature and advantage become apparent more, are described in detail the specific embodiment of the present invention below in conjunction with accompanying drawing.
Device embodiment one:
See Fig. 1, this figure is directed sound generation device embodiment one schematic diagram provided by the invention.
The directed sound generation device that the present embodiment provides, comprising: signal pre-processing module 100, Pulse width modulation module 200, drive amplification module 300 and ultrasound transducer array module 400;
Described signal pre-processing module 100, for carrying out bandpass filtering, gain amplification, low-frequency compensation and compression amplitude limiting processing successively to the digital audio and video signals of input, sends to described Pulse width modulation module by the signal after process;
It should be noted that, what signal pre-processing module 100 received is digital audio and video signals, if the reception of directed sound generation device is simulated audio signal, needs through AD converter, after simulated audio signal is converted to digital audio and video signals, then flow to signal pre-processing module 100.
The cut-off frequency of described band pass filter and pass band width are determined by the bandwidth of the super transducer of the bandwidth sum of described digital audio and video signals.
Gain amplification is carried out to filtered signal, the problem that in pulse width modulation, signal amplitude is less can be made up.
The main physically based deformation acoustics of low-frequency compensation and psychological model, the time domain Variation Features according to people's Er-frequency response curve and voice signal compensates for signal low frequency part.Low-frequency compensation can make up the poor problem of the low-frequency effect of the audible signal after demodulation.
Compression amplitude limiting processing is carried out to the signal after low-frequency compensation, wherein compression ratio can in the scope of 1.5-2 value, start-up time can in the scope of 50ms-70ms value.
Described Pulse width modulation module 200, for utilizing pulse width modulation to obtain modulated ultrasonic carrier signal the signal after described process;
Described drive amplification module 300, for carrying out drive amplification to described modulated ultrasonic carrier signal;
Described ultrasound transducer array module 400, for the modulated ultrasonic carrier signal after amplification is launched ultrasonic signal by LC low-pass filter circuit coupling ultrasonic sensor array, utilizes the aerial nonlinear propagation of ultrasonic signal to produce direct sound; The ultrasonic sensor array of described ultrasonic transducer comprises multiple array element, and the carrier frequency of described ultrasonic carrier signal is arranged according to the operating frequency of each described array element.
Ultrasound transducer array is formed primarily of LC low-pass filter circuit and ultrasonic sensor array, can select the staggered or hexagon weighting array of rectangle according to practical application scene.
The directed sound generation device that the present embodiment provides, utilizes Pulse width modulation module that ultrasonic carrier signal modulates audio signals is generated modulated ultrasonic carrier signal.The problem of and ultrasonic aerial low-frequency effect difference less in order to the signal amplitude solving pulse width modulation, has carried out preliminary treatment in front end to signal in the present invention, has comprised and carry out filtering, gain amplification, low-frequency compensation and compression amplitude limiting processing to signal.Because pulse width modulation is relatively simple for structure, distortion is less, and has good integration and Energy Efficiency Ratio.
Device embodiment two:
See Fig. 2, this figure is signal pre-processing module internal structure schematic diagram provided by the invention.
The signal pre-processing module that the present embodiment provides comprises: bandpass filtering submodule 101, gain amplify submodule 102, low-frequency compensation submodule 103 and compression amplitude limit submodule 104;
Bandpass filtering submodule 101, for carrying out bandpass filtering to the digital audio and video signals of input, all filters out the signal beyond cut-off frequency;
Submodule 102 is amplified in gain, amplifies for the signal exported bandpass filtering submodule;
Low-frequency compensation submodule 103, the signal exported for amplifying submodule to gain carries out low-frequency compensation;
Compression amplitude limit submodule 104, carries out compression amplitude limit for the signal after amplifying gain.
It should be noted that, be all corresponding with follow-up pulse width modulation and ultrasound transducer array for the preliminary treatment of signal in the present invention, in order to solve Problems existing in follow-up signal processing procedure.Thus just signal was processed before signal enters Pulse width modulation module, make up the drawback of Pulse width modulation module.Thus ensure that the signal that ultrasonic transducer exports is undistorted, and in the range of audibility.
In the present embodiment, described Pulse width modulation module carries out pulse width modulation according to following pulse width modulation transfer function and obtains described ultrasonic carrier signal:
S
o＝H
PWM{S
t}；
Wherein, S
ofor modulated ultrasonic carrier signal; S
tfor the digital audio and video signals of input; H
pWMfor pulse width modulation transfer function;
The frequency of described ultrasonic carrier signal is f
c; f
c=f
t-f
e;
Wherein, f
tfor the center operating frequency of array element in described ultrasound transducer array, f
efor the error compensation factor, f
e∈ [-100,0) and ∪ (0,100], so just can produce sub-audible sound.
F
eif it is comparatively large to depart from this condition, then sub-audible sound cannot be produced, if f
ebe 0 and can produce a kind of self-exited single-frequency noise, the masking effect of this noise due to sound when input digital audio signal time is easily flooded, but then can be clearly when input digital audio signal is zero.
Wherein, H
pWMfunction is by the frequency f of ultrasonic carrier signal
c, modulation ratio m and carrier wave ratio C
rdetermine.Modulation ratio m is S
tthe ratio of signal peak and ultrasonic carrier signal peak value Umax, carrier wave ratio C
rfor the frequency f of ultrasonic carrier signal
cwith S
tthe ratio of signal frequency.Because the ultrasonic signal of modulation belongs to nonlinear effect from demodulation, therefore H in atmosphere
pWMfunction generally need not represent by concrete analytical expression, and its optimal function is determined, according to H by the key parameter of experiment measuring
pWMoptimal function can design corresponding pwm circuit.
The center operating frequency f of array element in described ultrasound transducer array
tmeet the following conditions: 3f
sig≤ f
t≤ f
mos;
Wherein, f
sigfor the peak frequency of described digital audio and video signals, f
mosfor the peak frequency of described Pulse width modulation module breaker in middle device.
In theory, if pulse width modulation adopts rule sampling method, f
tbe greater than the f of twice
sigsampling thheorem can be met.This value is obviously the bigger the better, and requires that this value is greater than the f of 12 times in general D class power amplifier
sigbut modulated carrier must operate at supersonic range and must much smaller than the peak frequency f of switching device in directed method for acoustic
mos, determine f through experiment
tat 3 ~ 6 times of f
sigfor the best.
The unloaded duty ratio of described pulse width modulation is 50% ± 10%.
Wherein, the duty ratio of pulse width modulation is the ratio in high level pulse width time and modulated carrier cycle.In directed method for acoustic, this duty ratio is along with the digital audio and video signals of input constantly changes, and is Light Condition when the digital audio and video signals inputted is 0.Unloaded duty ratio, by the total distortion degree of ultrasonic signal in atmosphere after demodulation of impact modulation, affects minimum when unloaded duty ratio is 50%, when also namely the unloaded low and high level signal exported has a phase difference of 180 degree, the total distortion degree after demodulation is less.Along with the bias distortion of unloaded duty ratio will increase, distortion when departure degree is greater than 10% will have a strong impact on the sound quality of ultrasonic signal in atmosphere after demodulation of modulation.
Described signal pre-processing module, also for when described digital audio and video signals being detected for zero load, transmit control signal to described Pulse width modulation module, described Pulse width modulation module is closed.
The phase difference of any two array elements in described ultrasound transducer array is less than 90 degree.The phase difference of any two array elements is by the total distortion degree of ultrasonic signal in atmosphere after demodulation after impact modulation, along with the increase of phase difference, distortion also increases thereupon, will have a strong impact on the sound quality of ultrasonic signal in atmosphere after demodulation of modulation during more than 90 degree.Therefore, the phase difference of any two array elements is needed to be less than 90 degree.
The signal gain G=G determined by pwm pulse bandwidth modulation signals average power
1* G
2.
Wherein, G
1for the gain factor of signal gain, G
2for compressing the gain factor of amplitude limit.
limG*Max{S
i(t)}＝m*U
c；
Wherein, m is modulation ratio, U
cfor the peak value of modulated carrier signal.
Array element in the staggered or hexagon weighting array of described rectangle adopts and is connected in parallel, and center distance d between any two adjacent array elements is equal, and d meets following condition:
Wherein, r is the vibrating diaphragm radius of array element, f
cfor the frequency of ultrasonic carrier signal, c is ultrasonic transducer propagation velocity in media as well.
Such as, the half-wavelength of 40KHz ultrasonic carrier signal in homogeneous air is 4.25mm, but usually the vibrating diaphragm radius r of array element is greater than this value, the therefore generation of secondary lobe in inevitable array beams.These secondary lobes will have a strong impact on the directive property of array, therefore for suppressing these secondary lobes, need d little as far as possible, and center distance between any two array elements be equal.But array element itself also has encapsulation, and mounting means also affects d in addition, and these errors are determined be less than quarter-wave according to theory deduction and experiment.
Wherein, d value is also by the total harmonic distortion of the modulated ultrasonic signal of impact in atmosphere after demodulation, and its optimal value also affects by the formation of ultrasonic transducer and the quantity n of array element.
In addition, the quantity n of array element also affects the directive property of array, and n its directive property larger is relatively better.
It should be noted that, LC low-pass filter circuit mainly in order to solve the adaptation issues of the staggered or hexagon weighting array of rectangle, for eliminating the noise that the high-frequency harmonic that produces in pwm process and switching device produce.
Because the sonac array element in the ultrasonic transducer usually selected is piezoelectric transducer, therefore directly can provide the electric capacity in LC low-pass filter circuit by the array element of multiple parallel connection, its equivalent capacitance value is:
Ce＝nC；
Wherein, C is the direct capacitance of array element, and n is the quantity of array element.
Electric capacity in described LC low-pass filter circuit is realized by the equivalent capacity in described ultrasound transducer array, and the inductance L e in described LC low-pass filter circuit meets the following conditions:
Wherein f
cfor the frequency of ultrasonic carrier signal, C is the direct capacitance of array element in described ultrasound transducer array, and n is the quantity of array element in described ultrasound transducer array.
Such as, the directed acoustic device that the above embodiment of the present invention provides, can be applied on the VTM/ATM machine of bank, the audio frequency that VTM/ATM machine exports can send directed sound through this directed acoustic device, make user only can hear the audio content that VTM/ATM machine sowing is put in limited fixed range, effectively ensure that fail safe and the privacy of the content of audio frequency.
In addition, the directed acoustic device that the embodiment of the present invention provides, also can be applied on the exhibition position in museum, and the directed sound of generation can ensure that the spectators in this region, exhibition position can listen, and the spectators of other exhibition positions are not by the interference of this exhibition position sound.Effectively reduce the noisy property of environment, reduce the noise pollution in PE.
Based on the directed acoustic device of one that above embodiment provides, the embodiment of the present invention also provides a kind of directed sound production method, introduces in detail below in conjunction with accompanying drawing.
Embodiment of the method one:
See Fig. 3, this figure is directed sound production method embodiment one flow chart provided by the invention.
The directed sound production method that the present embodiment provides, comprises the following steps:
S301: bandpass filtering, gain amplification, low-frequency compensation and compression amplitude limiting processing are carried out successively to the digital audio and video signals of input;
It should be noted that, if the reception of directed sound generation device is simulated audio signal, needs through AD converter, after simulated audio signal is converted to digital audio and video signals, then carry out bandpass filtering.
Gain amplification is carried out to filtered signal, the problem that in pulse width modulation, signal amplitude is less can be made up.
The main physically based deformation acoustics of low-frequency compensation and psychological model, the time domain Variation Features according to people's Er-frequency response curve and voice signal compensates for signal low frequency part.Low-frequency compensation can make up the poor problem of the low-frequency effect of the audible signal after demodulation.
Compression amplitude limiting processing is carried out to the signal after low-frequency compensation, wherein compression ratio can in the scope of 1.5-2 value, start-up time can in the scope of 50ms-70ms value.
S302: utilized by the signal after described process pulse width modulation to obtain the ultrasonic carrier signal after modulating;
S303: drive amplification is carried out to described ultrasonic carrier signal;
S304: utilize ultrasound transducer array to launch ultrasonic signal modulated ultrasonic carrier signal after amplification, utilizes the aerial nonlinear propagation of ultrasonic signal to produce direct sound.
Ultrasound transducer array is formed primarily of LC low-pass filter circuit and ultrasonic sensor array, can select the staggered or hexagon weighting array of rectangle according to practical application scene.
The directed sound generation device that the present embodiment provides, utilizes Pulse width modulation module modulates audio signals ultrasonic carrier signal.The problem of and ultrasonic aerial low-frequency effect difference less in order to the signal amplitude solving pulse width modulation, has carried out preliminary treatment in front end to signal in the present invention, has comprised and carry out filtering, gain amplification, low-frequency compensation and compression amplitude limiting processing to signal.Because pulse width modulation is relatively simple for structure, distortion is less, and has good integration and Energy Efficiency Ratio, therefore, this device provided by the invention can be applied in civil area, such as, the sales counter ATM of bank can be applied in, the occasions such as the window of hospital, the explanation platform in museum.
Describedly utilize pulse width modulation to obtain modulated ultrasonic carrier signal, specifically utilize following pulse width modulation transfer function to carry out:
S
o＝H
PWM{S
t}；
Wherein, S
ofor modulated ultrasonic carrier signal; S
tfor the digital audio and video signals of input; H
pWMfor pulse width modulation transfer function;
The frequency of described ultrasonic carrier signal is f
c; f
c=f
t-f
e;
Wherein, f
tfor the center operating frequency of array element in described ultrasound transducer array, f
tbe greater than 20kHz; f
efor the error compensation factor, f
e∈ [-100,0) ∪ (0,100].
Such as, the method that the above embodiment of the present invention provides, can be applied on the VTM/ATM machine of bank, the audio frequency that VTM/ATM machine exports can send directed sound through this directed acoustic device, make user only can hear the audio content that VTM/ATM machine sowing is put in limited fixed range, effectively ensure that fail safe and the privacy of the content of audio frequency.
In addition, the method that the embodiment of the present invention provides, also can be applied on the exhibition position in museum, and the directed sound of generation can ensure that the spectators in this region, exhibition position can listen, and the spectators of other exhibition positions are not by the interference of this exhibition position sound.Effectively reduce the noisy property of environment, reduce the noise pollution in PE.
The above is only preferred embodiment of the present invention, not does any pro forma restriction to the present invention.Although the present invention discloses as above with preferred embodiment, but and be not used to limit the present invention.Any those of ordinary skill in the art, do not departing under technical solution of the present invention ambit, the Method and Technology content of above-mentioned announcement all can be utilized to make many possible variations and modification to technical solution of the present invention, or be revised as the Equivalent embodiments of equivalent variations.Therefore, every content not departing from technical solution of the present invention, according to technical spirit of the present invention to any simple modification made for any of the above embodiments, equivalent variations and modification, all still belongs in the scope of technical solution of the present invention protection.
Claims (12)
1. a directed sound generation device, is characterized in that, comprising: signal pre-processing module, Pulse width modulation module, drive amplification module and ultrasound transducer array module;
Described signal pre-processing module, for carrying out bandpass filtering, gain amplification, low-frequency compensation and compression amplitude limiting processing successively to the digital audio and video signals of input, sends to described Pulse width modulation module by the signal after process;
Described Pulse width modulation module, for utilizing pulse width modulation to obtain modulated ultrasonic carrier signal the signal after described process;
Described drive amplification module, for carrying out drive amplification to described modulated ultrasonic carrier signal;
Described ultrasound transducer array module, for the modulated ultrasonic carrier signal after amplification is launched ultrasonic signal by LC low-pass filter circuit coupling ultrasonic sensor array, utilizes the aerial nonlinear propagation of ultrasonic signal to produce direct sound; Ultrasonic sensor array in described ultrasonic transducer comprises multiple array element, and the carrier frequency of described ultrasonic carrier signal is arranged according to the operating frequency of each described array element.
2. directed sound generation device according to claim 1, is characterized in that, described Pulse width modulation module carries out pulse width modulation according to following pulse width modulation transfer function and obtains described modulated ultrasonic carrier signal:
S
o＝H
PWM{S
t}；
Wherein, S
ofor modulated ultrasonic carrier signal; S
tfor the digital audio and video signals of input; H
pWMfor pulse width modulation transfer function;
The frequency of described ultrasonic carrier signal is f
c; f
c=f
t-f
e;
Wherein, f
tfor the center operating frequency of array element in described ultrasound transducer array, f
efor the error compensation factor, f
e∈ [-100,0) ∪ (0,100].
3. directed acoustic device according to claim 2, is characterized in that, the center operating frequency f of array element in described ultrasound transducer array
tmeet the following conditions: 3f
sig≤ f
t≤ f
mos;
Wherein, f
sigfor the peak frequency of described digital audio and video signals, f
mosfor the peak frequency of described Pulse width modulation module breaker in middle device.
4. directed acoustic device according to claim 1 and 2, is characterized in that, the unloaded duty ratio of described pulse width modulation is 50% ± 10%.
5. directed acoustic device according to claim 1, is characterized in that, the phase difference of any two array elements in described ultrasound transducer array is less than 90 degree.
6. directed acoustic device according to claim 1, it is characterized in that, described signal pre-processing module, also for when described digital audio and video signals being detected for zero load, transmit control signal to described Pulse width modulation module, described Pulse width modulation module is closed.
7. directed acoustic device according to claim 1, is characterized in that, the cut-off frequency of described band pass filter and pass band width are determined by the bandwidth of the bandwidth sum ultrasonic transducer of described digital audio and video signals.
8. directed acoustic device according to claim 1, is characterized in that, the formation of the ultrasonic sensor array of described ultrasound transducer array is the staggered or hexagon weighting array of rectangle.
9. directed acoustic device according to claim 8, is characterized in that, the array element in the staggered or hexagon weighting array of described rectangle adopts and is connected in parallel, and center distance d between any two adjacent array elements is equal, and d meets following condition:
Wherein, r is the vibrating diaphragm radius of array element, f
cfor the frequency of ultrasonic carrier signal, c is ultrasonic transducer propagation velocity in media as well.
10. directed acoustic device according to claim 1, it is characterized in that, electric capacity in described LC low-pass filter circuit is provided by the equivalent capacity of sonac array element in described ultrasound transducer array, and the inductance L e in described LC low-pass filter circuit meets the following conditions:
Wherein f
cfor the frequency of ultrasonic carrier signal, C is the direct capacitance of array element in described ultrasound transducer array, and n is the quantity of array element in described ultrasound transducer array.
11. 1 kinds of directed sound production methods, is characterized in that, comprise the following steps:
Bandpass filtering, gain amplification, low-frequency compensation and compression amplitude limiting processing are carried out successively to the digital audio and video signals of input;
Pulse width modulation is utilized to obtain modulated ultrasonic carrier signal the signal after described process;
Drive amplification is carried out to described brewed ultrasonic carrier signal;
Utilize LC low-pass filter circuit coupling ultrasonic sensor array to launch ultrasonic signal the brewed ultrasonic carrier signal after amplifying, utilize the aerial nonlinear propagation of ultrasonic signal to produce direct sound.
12. directed sound production methods according to claim 11, is characterized in that, describedly utilize pulse width modulation to obtain modulated ultrasonic carrier signal, specifically utilize following pulse width modulation transfer function to carry out:
S
o＝H
PWM{S
t}；
Wherein, S
ofor modulated ultrasonic carrier signal; S
tfor the digital audio and video signals of input; H
pWMfor pulse width modulation transfer function;
The frequency of described ultrasonic carrier signal is f
c; f
c=f
t-f
e;
Wherein, f
tfor the center operating frequency of array element in described ultrasound transducer array, f
tbe greater than 20kHz; f
efor the error compensation factor, f
e∈ [-100,0) ∪ (0,100].
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| CN108805086A (en) * | 2018-06-14 | 2018-11-13 | 联想(北京)有限公司 | A kind of media control method and apparatus for processing audio |
| WO2019041494A1 (en) * | 2017-08-29 | 2019-03-07 | 山东科技大学 | Directional acoustic wave emission device and method for repelling birds |
| CN111083603A (en) * | 2018-10-19 | 2020-04-28 | 知微电子有限公司 | Sound producing apparatus |
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