Background
With the development and progress of science and technology, the requirement of sensing the outside world by people by science and technology is increasingly improved, the performance index of the traditional sensor can not meet the requirements of people in the fields of medical treatment, military, remote sensing and the like, and the high-sensitivity acoustic sensor is also a hot point of attention in the sensing field. Existing acoustic sensors sense acoustic signals through the response of a passive transducer to an acoustic stimulus. For example, the capacitive acoustic sensor is implemented by converting acoustic vibration into an electrical signal by generating capacitance change through plate-pole vibration of a capacitive membrane under acoustic excitation, wherein the vibration of the capacitive membrane is passive vibration under the acoustic excitation. In order to achieve high sensing sensitivity, the prior art is to improve various parameters by using new materials and the like in such a passive acoustic sensing mode. However, the effect of these improvements is limited by the operating principle of such passive sensing.
Relevant researches on auditory periphery show that auditory hair cells can modulate the vibration of a basement membrane through electrostriction of cell bodies and cilium swinging to compensate the viscous resistance of the basement membrane in a lymph fluid environment, so that the basement membrane becomes a Hopf oscillator at a bifurcation point, an active amplification effect is generated on weak acoustic signals, and high-sensitivity acoustic sensing of an auditory system is realized. The working mode of the high-sensitivity sound sensing realized by active driving in the auditory perception of the biological system is the subversion of the existing sound sensing theory and technology. Based on the understanding of the mechanism of active force generation of hair cells in cochlea, the invention firstly uses the acoustic sensing mode of organisms for applying the acoustic sensing mode to acoustic sensing to establish the active acoustic sensing technology based on auditory sense, which is different from the prior passive acoustic sensing and the acoustic sensor based on the technology. The sensor has obviously improved sensitivity compared with a passive acoustic sensor, and meanwhile, the sensor also has good detection effect on periodic signals with specific frequency in noise, and the detection value of weak acoustic signals in the fields of medicine, underwater sound, military and the like is particularly important.
Disclosure of Invention
Aiming at the limitation of the prior art, the invention aims to construct a new acoustic sensing technology based on new cognition of an auditory perception mechanism, namely an active acoustic sensing technology, and key technical details of the active acoustic sensor such as an overall scheme, active driving arrangement, driving realization, a driving control equation and the like of the active acoustic sensor based on the technology.
The new technology of sound sensing subversion based on the auditory active sensing mechanism provided by the invention is as follows:
1. providing active excitation for the acoustic response component of the acoustic sensor to enable the acoustic response component to become an active vibrator;
2. the active excitation makes the acoustic response component at the branching point of the Hopf oscillator;
the specific implementation scheme based on the active acoustic sensing technology provided by the invention comprises the following steps: the vibration detection device comprises a vibrating diaphragm used for responding to sound field change, a displacement detection module, a driving module used for providing main power, and an active driving modulation module used for enabling a driven vibrator to be located at a Hopf bifurcation point. The input end of the displacement detection module is connected with the vibrating diaphragm in a manner of a capacitor plate, an optical fiber and the like and is used for detecting the displacement response x (t) of the vibrating diaphragm in a sound field; the input end of the active modulation module is connected with the output end of the displacement detection module, and the output end of the active modulation module is connected with the diaphragm and is used for generating active excitation F (t) according to the response signal x (t) and modulating the vibration of the diaphragm.
Still further, the active modulation module comprises: a modulation circuit and an active excitation module; the modulation circuit is used for generating a modulation signal according to a signal fed back by the diaphragm in real time; the active excitation module is used for generating an active acting force according to the modulation signal and modulating the vibration of the diaphragm.
And further controlling the active excitation module to generate active excitation F (t) on the diaphragm by the modulation circuit so that the diaphragm becomes a Hopf oscillator in a critical state (bifurcation point).
Further preferably, a size of
Active excitation f (t); wherein x is the displacement of the part of the diaphragm, and gamma
αFor the active excitation coefficient, the adjustable parameter B is the electrostrictive coefficient, and the adjustable parameter x0 is the diaphragm balance position offset compensation.
Still further, the active excitation module includes: one end of the piezoelectric ceramic is connected to the output end of the modulation circuit, one end of the elastic fiber is connected to the other end of the piezoelectric ceramic, and the other end of the elastic fiber is connected with the vibrating diaphragm; the piezoelectric ceramic stretches and retracts according to the signal of the modulation circuit and drives the elastic fiber to move, and therefore vibration of the vibrating diaphragm is modulated.
Furthermore, the piezoelectric ceramic generates electrostrictive effect according to the modulation signal s (t) to drive the elastic fiber to vibrate, thereby applying active excitation F (t) to the diaphragm.
Still further, the acoustic sensor further comprises: and the input end of the signal processing module is connected with the output end of the displacement detection module and is used for processing the modulated response signal to obtain an acoustic sensing signal y (t).
Compared with a passive acoustic sensor, the invention has obvious amplification effect on signals with smaller sound pressure level, thereby being capable of obviously improving the response of the sensor to weak signals and further improving the sensitivity.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In order to improve the sensitivity of the existing passive acoustic sensor, the invention simulates the active amplification effect of cochlear capillary cells on a basement membrane, and combines the traditional vibrating diaphragm acoustic sensor, such as a capacitor microphone and a vibrating diaphragm optical fiber microphone, so as to construct a novel active acoustic sensor with active mechanism participation. Analysis shows that the active acoustic sensor has high sensitivity and good detection capability on weak periodic signals with specific frequency in noise, and the adopted specific technical scheme is as follows:
(1) for acoustic sensors that respond to vibration as an acoustic stimulus, the active stimulus makes them an active vibrator rather than the passive vibrator of conventional acoustic sensors.
(2) Active excitation makes the sensor a Hopf element that stays at the bifurcation point.
(3) The generation of the active excitation may employ the following scheme.
Based on the results of the cochlear related physiological experiments, we propose a velocity-dependent adaptive force f regulated by the electrostriction of outer hair cells and ciliary movement
a. Its simplified expression form is as follows:
wherein z is the displacement of this part of the basement membrane, γ
βIs the adaptive force coefficient, C is the outer hair cell electrostrictive coefficient, z
0The primary length of the outer hair cells. The invention builds active excitation for modulating diaphragm vibration in acoustic sensing by analogy with the form of adaptive force in cochlea
Wherein x is the displacement of the part of the acoustic sensing diaphragm, and gamma
αFor the active excitation coefficient, the adjustable parameter B is the electrostrictive coefficient, and the adjustable parameter x0 is the diaphragm balance position offset compensation. And adjusting the parameters according to the actual condition to obtain the required active excitation. For example, adjusting the parameters x0, B can change the trend of the active excitation f (t) along with the vibration response x of the diaphragm, thereby generating different sensing response results. See fig. 4, 5 for details.
(4) Active modulation module design
The active modulation module comprises a modulation circuit and an active excitation module. The modulation circuit generates a modulation signal according to the active force expression form in the step (3) by using the signal fed back by the diaphragm in real time; the active excitation module generates active acting force to modulate vibration of the diaphragm according to the modulation signal. (e.g., an active excitation module comprising a piezoelectric ceramic and an elastic fiber, wherein two ends of the elastic fiber are connected to the piezoelectric ceramic and the diaphragm, respectively. A novel active acoustic sensor can be obtained by adding an active modulation module design on the basis of the traditional acoustic sensor.
The present invention will be described in further detail with reference to the accompanying drawings and specific examples.
On the basis of understanding of the mechanism of active force generation of hair cells in the cochlea, the invention establishes an active dynamic model for cochlear signal processing, and designs a novel active acoustic sensor based on the mechanism of active amplification of the hair cells by utilizing the model principle. The sensor simulates the active amplification regulation and control effect of capillary cells on a basement membrane, and modulates the vibrating membrane of the acoustic sensor by introducing an active amplification regulation and control module to compensate air resistance, so that the vibrating membrane is similar to the basement membrane in a cochlea and becomes a Hopf oscillator, and the acoustic sensing sensitivity is improved. Meanwhile, the sensor also has good detection effect on periodic signals with specific frequency in noise, so that the sensor can be used for detecting weak signals in noise in the fields of underwater sound, military affairs and the like.
As shown in fig. 1, the acoustic sensor based on the active amplification mechanism includes: a diaphragm for responding to sound field changes, a displacement detection module (such as a capacitance or optical fiber displacement detection module), an active modulation module, and a subsequent signal processing module. One end of the displacement detection module is connected with the vibrating diaphragm to detect the displacement response x (t) of the vibrating diaphragm in a sound field, and the other end of the displacement detection module is connected with the active modulation module and the signal processing module and used for transmitting the detected response information. The active modulation module is respectively connected with the displacement detection module and the vibrating diaphragm and generates active excitation F (t) to modulate the vibration of the vibrating diaphragm according to the response signal received from the displacement detection module. The signal processing module is used for performing corresponding signal processing (such as filtering) on the modulated response signal to obtain a required acoustic sensing signal y (t).
The active modulation module includes: a modulation circuit and an active excitation module. The modulation circuit is used for generating a modulation signal s (t) for controlling the active excitation module to generate a magnitude of
Active excitation f (t). The active excitation module can be composed of piezoelectric ceramics and elastic fibers. The piezoelectric ceramic generates electrostrictive effect according to the modulation signal s (t) to drive the elastic fiber to vibrate, so that active excitation F (t) is applied to the vibrating diaphragm.
The concrete working flow of the acoustic sensor based on the active amplification mechanism is as follows: the real-time vibration signal x (t) of the diaphragm in the sound field is first detected by conventional acoustic detection means (e.g. capacitive or fiber optic detection). Then, a modulation circuit in the active modulation module generates a modulation signal s (t) according to the real-time response signal x (t) of the diaphragm to control an active force action device to generate active excitation F (t) (for example, to generate a corresponding electrical signal to cause the piezoelectric ceramic to deform in a stretching manner) to actively modulate the vibration of the diaphragm in real time. And finally, obtaining a sensing signal y (t) after the processing of the signal processing module. The magnitude of the active excitation f (t) increases as the response amplitude of the diaphragm decreases as shown in figure 4 (a). Analysis shows that when the external acoustic signal is small, the active modulation module generates large active excitation, effective damping of the system is reduced, amplification of small signals is achieved, and sensitivity of acoustic sensing is improved.
FIG. 2 is a graph of response of active and passive systems as a function of sound intensity. As shown in the figure, compared with a passive acoustic sensor, the acoustic sensor based on the active amplification mechanism has a significant amplification effect on a signal with a small sound pressure level, so that the response of the sensor to a weak signal can be significantly improved, and the sensitivity can be improved.
Fig. 3 is a comparative image of the single-frequency signal extraction function of the active acoustic sensor and the passive system, in which a solid line with cross marks represents a curve of a response value of the active system at 425hz as a function of a sinusoidal signal amplitude, and a solid line with cross marks represents a curve of a response value of the passive system at 425hz as a function of a sinusoidal signal amplitude. The external sound field is represented by the following formula Fw(t) ═ Asin (2 pi ft) + wgn, which contains a sinusoidal signal and constant white gaussian noise. And the amplitude of the sinusoidal signal is gradually increased, and the sinusoidal signal is extracted by comparing the active system with the passive system. It can be seen from the figure that the active system can extract the sine signal when the amplitude of the sine signal is 100dB, and the passive system can extract the sine signal when the amplitude of the sine signal is 300dB, so that the active acoustic sensing has a good amplification effect on the periodic signal with a specific frequency.
FIG. 4(a) is a graph of the relationship between the active excitation F (t) and the diaphragm response x when the parameter x0 takes different values; FIG. 4(b) is a graph showing the relationship between the diaphragm response and the sound pressure level of the external acoustic signal under the active excitation when the parameter x0 has different values; as can be seen from fig. 4(a), changing the parameter x0 changes the magnitude of the active excitation f (t), thereby affecting the sense response. It can be seen from fig. 4(b) that the larger x0, the greater the active amplification range of the sound pressure level of the acoustic signal by the transducer.
FIG. 5(a) is a graph showing the relationship between the active excitation F (t) and the diaphragm response x when the parameter B takes different values; FIG. 5(B) is a graph showing the relationship between the response of the diaphragm and the sound pressure level of the external sound signal under the action of the active excitation when the parameter B has different values; as can be seen from fig. 5(a), changing the parameter B can change the magnitude of the active excitation f (t), thereby affecting the sense response. It can be seen from fig. 5(B) that the smaller B, the larger the active amplification range of the sound pressure level of the acoustic signal by the sensor.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.