Electroacoustic Sensor Research Articles

Highly sensitive Fabry-Perot acoustic sensor based on optic fiber spherical end surface

This paper presents and experimentally validates a highly sensitive fiber-optic Fabry-Perot interferometer sound sensor based on a fiber-optic spherical structure. The Fabry-Perot interferometer comprises an aluminum foil diaphragm and a fused fiber-optic microsphere end face, both sealed in a structure made of a glass tube. An optical fiber microsphere structure is used for the first time in acoustic sensing. Based on the strong focusing capability of the microsphere, the high coupling efficiency to the reflected beam, and the extensive range of the focused convergent optical field formed, the focused convergent optical fields facilitate the sensing of an extensive range of motion or deformation of the cavity compared to the divergent optical field of a flat fiber end face, i.e., the acoustic signals at more minor sound pressures can also be well sensed, thus compared to a flat fiber end face fiber The acoustic sensor can monitor acoustic signals over a more extensive frequency range and a larger range of acoustic pressure variations, and the output voltage signal is of a larger amplitude at the same acoustic signal, which allows the monitoring of acoustic signals at acoustic frequencies within the hearing range of the human ear. Experimental results show that the sensor shows a flat frequency response in the range of 20 Hz–20 kHz, covering all frequency components of the human ear hearing range, and the signal-to-noise ratio of the proposed acoustic sensor in the range of 20 Hz–20 kHz is greater than that of the flat fiber end-surface based acoustic sensor and the reference electroacoustic sensor, especially The sensor has the advantages of good high sensitivity, excellent linearity, wide planar response range, and simple manufacturing process. It can potentially be used as a highly sensitive, high acoustic quality fiber optic microphone in practical applications.

Intracochlear noise-induced vibrations

When designing an engineered electroacoustic sensor, a key question is “what is the lowest level sound that can be sensed?” To answer this, we design to achieve a desired input referred noise. In the cochlea, there are many sources of internal noise, such as Johnson noise arising from membrane conductances, clatter noise in channels, and thermoviscous damping that will conspire to cause vibrational responses in the absence of external stimulus. Noise can dramatically affect our ability to sense desired sounds. Experimental and theoretical cochlear mechanics has focused on determining the sensitivity of the cochlea. However, to our knowledge, there is only one set of published measurements of the displacement response of the cochlea in quiet (the levels are low, below 1 atto-meter2 per Hz), and no simulations in a global cochlear model of the noise response. We introduce a method for predicting the global response to noise from electromotile outer hair cells in the cochlea for small fluctuations about equilibrium using our finite-element based numerical model. Furthermore, we show the relative contribution of different noise sources (in particular, channel noise versus conductance noise) and the spatial distribution of the response to these sources.

Calibration of a Hail-Impact Energy Electroacoustic Sensor

Calibration of a Hail-Impact Energy Electroacoustic Sensor

Energy harvesting and self-powered microphone application on multifunctional inorganic-organic hybrid nanogenerator

Piezoelectric nanogenerators are forthcoming alternative choices for scavenging different types of wasted mechanical energies. An inorganic-organic hybrid piezoelectric nanogenerator (HPNG) has been realized by incorporating zinc sulphide nanorods (ZnS-NRs) into electrospun poly(vinylidene fluoride) (PVDF) nanofibers for self-powered multifunctional sensing. As an acoustic energy harvester, the HPNG possesses a resonance frequency of 86 ± 3 Hz and an acoustic sensitivity of ∼3 V Pa−1. It can distinguish sound waves from low to mid frequency region that makes it suitable for noise detection. In addition, HPNG demonstrates the very high wind energy conversion efficiency of ∼58% that make it capable of detecting human exhalation. Apart from its noise detection and power generation capabilities, HPNG is possible to use as a self-powered microphone. This electromechanical coupling, integrated with their flexibility, makes it usable as a flexible electro-acoustic sensor for security purpose as well. These results establish the potential of hybrid piezoelectric structure, with their multi functionalities for several promising applications such as noise detection, wind energy harvesting, security monitoring and most promisingly to develop the self-powered system.

Electro-acoustic sensor for the real-time identification of the bacteriophages

The electro-acoustical sensor for the real-time identification of the bacteriophage FAl-SR65 is described. The polyclonal antibodies specific to the bacteriophage FAl-SR65 were for the first time obtained, and the possibility of their application to the bacteriophage detection by using the electro-acoustical method of analysis was also studied for the first time. The electro-acoustical sensor was based on the lateral electric field excited piezoelectric resonator. The frequency dependences of the real and imaginary parts of the electrical impedance of such a resonator, loaded with the virus-antibody suspension, significantly differed from those measured for the same resonator with the same virus suspension but without antibodies (control). The limit for the reliable bacteriophage detection during their interaction with the antibodies (sensitivity level) was determined to be 106 phages ml−1. The obtained results demonstrate the possibility to record the bacteriophage–antibody interactions and can be used as the basis for the development of the biological sensor for the quantitative virus detection.

An acoustic method for the analysis of bacterial cells

The application of a biological electroacoustic sensor based on a lateral electric-field-excited piezoelectric resonator for the study of bacterial cells that interact with specific bacteriophages, mini-antibodies, and polyclonal antibodies was successfully demonstrated. The determined lower limit of microbialcell detection was approximately of 103 to 104 cells/mL for the duration of the assay of 10 min. The possibility of bacterial-cell detection via interaction with specific agents in the presence of extraneous microbiota was shown. The method allowed us to determine the spectrum of lytic activity of bacteriophages and the sensitivity of microbial cells to bacteriophages. The results of the study showed that application of a sensor piezoelectric lateral-field resonator is a promising technique for the detection and identification of microbial cells and determination of their phage resistance in microbiology, medicine, and veterinary medicine. Furthermore, the results of the experiments made it possible to understand the mechanisms of the processes that occur in a suspension of bacterial cells in the presence of various biological agents. The method also may provide useful information regarding biophysical mechanisms of interactions that occur in microbial populations.

Obtaining phage mini-antibodies and using them for detection of microbial cells with an electroacoustic sensor

Phage mini-antibodies to bacterial cells of strain Azospirillum brasilense Sp245 were obtained, and the possibility of using them for detection of microbial cells with a lateral field excited piezoelectric resonator was studied. It has been found that the frequency dependences of the real and imaginary parts of electrical impedance of such a resonator loaded with a suspension of A. brasilense Sp245 cells with the mini-antibodies differ significantly from the dependences of the resonator with a control cell suspension without mini-anti-bodies. The limit of possible determination of the concentration of microbial cells is found to be 103 cells/mL upon interaction with mini-antibodies. It has been ascertained that detection of A. brasilense Sp245 cells with the aid of mini-antibodies is possible even in the presence of other cultures, for example, E. coli BL-Ril and A. brasilense Sp7. Therefore, it has been shown for the first time that detection of microbial cells with an electroacoustic sensor is feasible.

Estimation of the lactate threshold using an electro acoustic sensor system analysing the respiratory air

The lactate threshold is used by athletes to optimise the intensity during exercise. It is of interest to measure the threshold on the very day and during the present sport activity. Steady state ergometer tests have been performed on 40 individuals to compare the threshold found by an electro acoustic sensor system to the lactate threshold established by blood analyses evaluated with the Dmax method. The correlation coefficient between the threshold found by the sensor system and the one established by blood analyses regarding workload (Watt), heart rate (beats/min), and lactate level (mmol lactate/l blood) at the thresholds were 0.87 (p < 0.001), 0.74 (p < 0.001), and 0.65 (p < 0.001), respectively. The findings in this study indicates that the thresholds of individuals measured by the sensor system show good correlations to the threshold established with the Dmax method from lactate levels in blood samples.

A new capnograph based on an electro acoustic sensor

End tidal carbon dioxide measurements with an electro acoustic capnograph prototype have been demonstrated. The aim of this study was to verify that it is possible to obtain an adequate capnogram using the prototype and to investigate the influence of ambient temperature and humidity variations. By simultaneous measurements with a reference capnograph, on subjects performing exercise, hypo- and hyperventilation, P(ET)CO(2) readings from the reference were compared with the output signal from the prototype. The capnogram from the prototype correlated well with the reference in terms of breath time. The first parts of the expiration and inspiration phases were steeper for the reference than the prototype. The output signal from the prototype correlated well with the reference P(ET)CO(2) readings with a correlation coefficient of 0.93 at varied temperature and relative humidity.

Determination of optimum response requrements for underwater fiber-optic and electroacoustic transducers

To aid in the design of new sensors the methodology of determining the optimum sensitivity, linearity, and dynamic range requirements of underwater acoustic sensors is described. The relationships between the commonly specified ‘‘rated’’ sensitivity and its ‘‘absolute’’ detectability are explored in terms of the required minimum and maximum detectable signal levels and background noise in the operating environment and signal conditioning equipment. Performance limitations of fiber-optic and electroacoustic sensor designs and cost tradeoffs between the sensor and signal conditioning equipment are compared.