Sensitivity Of Microphone Research Articles

Vibration Sensitivity of One-Port and Two-Port MEMS Microphones

Vibration Sensitivity of One-Port and Two-Port MEMS Microphones

Piezoelectric Micromachined Microphone with High Acoustic Overload Point and with Electrically Controlled Sensitivity.

Currently, the most advanced micromachined microphones on the market are based on a capacitive coupling principle. Capacitive micro-electromechanical-system-based (MEMS) microphones resemble their millimetric counterparts, both in function and in performance. The most advanced MEMS microphones reached a competitive level compared to commonly used measuring microphones in most of the key performance parameters except the acoustic overload point (AOP). In an effort to find a solution for the measurement of high-level acoustic fields, microphones with the piezoelectric coupling principle have been proposed. These novel microphones exploit the piezoelectric effect of a thin layer of aluminum nitride, which is incorporated in their diaphragm structure. In these microphones fabricated with micromachining technology, no fixed electrode is necessary, in contrast to capacitive microphones. This specificity significantly simplifies both the design and the fabrication and opens the door for the improvement of the acoustic overload point, as well as harsh environmental applications. Several variations of piezoelectric structures together with an idea leading to electrically controlled sensitivity of MEMS piezoelectric microphones are discussed in this paper.

Simple in-system control of microphone sensitivities in an array

Abstract. A method to perform measurements of microphone responses directly in the array of a sensor system is described. It can be applied in reverberant environments and does not require high instrumentation effort. Due to the use of internal hardware of the sensor system, the whole signal chain of microphone–preamplifier–analogue-to-digital converter is characterized. The method was successfully tested for calibration of two types of planar arrays constructed with micro-electromechanical system (MEMS) microphones. Presented experimental results illustrate achieved performance, and possible application scenarios are discussed.

A behavioral nonlinear modeling implementation for MEMS capacitive microphones

We are highlighting the behavioral nonlinear system-level modeling approach for MEMS capacitive microphones. The combination of finite element modeling and large signal nonlinear circuit modeling provides a strong capability to predict electroacoustical performance for capacitive transductions. Circuit simulation tools such as Cadence Virtuoso have emerged as powerful aids in designing behavioral models in both linear and nonlinear regimes. Typical small signal lumped element models fail to capture the MEMS behavior which changes over pressure and electrical bias conditions. The models described herein capture diaphragm displacement and capacitance change over large pressure ranges for a simply supported circular plate. This can be coupled with the electrostatic force, due to the applied bias voltage, and converted back to pressure, thereby realizing a feedback loop in the circuit model. The nonlinear model capability is extended to predict capacitance-bias behavior and estimate pull-in of the MEMS device. The microphone sensitivity, signal-to-noise ratio, and harmonic distortions are accurately predicted using the nonlinear large signal model when compared to measured microphone data.

Fast Demodulated White-light Interferometry-based Measurement and Theoretical Verification of Mechanical Sensitivity of MEMS Biomimetic Microphone with Fiber-optic Fabry-Perot Interferometer

Fast Demodulated White-light Interferometry-based Measurement and Theoretical Verification of Mechanical Sensitivity of MEMS Biomimetic Microphone with Fiber-optic Fabry-Perot Interferometer

Fiber-Optic Hydraulic Sensor Based on an End-Face Fabry–Perot Interferometer with an Open Cavity

The paper describes the design and manufacturing process of a fiber optic microphone based on a macro cavity at the end face of an optical fiber. The study explores the step-by-step fabrication of a droplet-shaped macro cavity on the optical fiber’s end surface, derived from the formation of a quasi-periodic array of micro-cavities due to the fuse effect. Immersing the end face of an optical fiber with a macro cavity in liquid leads to the formation of a closed area of gas where interfacial surfaces act as Fabry–Perot mirrors. The study demonstrates that the macro cavity can act as a standard foundational element for diverse fiber optic sensors, using the droplet-shaped end-face cavity as a primary sensor element. An evaluation of the macro cavity interferometer’s sensitivity to length alterations is presented, highlighting its substantial promise for use in precise fiber optic measurements. However, potential limitations and further research directions include investigating the influence of external factors on microphone sensitivity and long-term stability. This approach not only significantly contributes to optical measurement techniques but also underscores the necessity for the continued exploration of the parameters influencing device performance.

Sound source direction-of-arrival estimation method for microphone array based on ultra-weak fiber Bragg grating distributed acoustic sensor.

A sound source direction-of-arrival (DOA) estimation method for microphone array based on ultra-weak fiber Bragg grating (UW-FBG) distributed acoustic sensor is proposed. The principle of acoustic signal demodulation is introduced, the sound pressure sensitivity and frequency response range of a single UW-FBG microphone are analyzed, and a series linear array with three UW-FBG microphones is designed. Combined with convolutional recurrent neural networks, the DOA estimation method is developed. Log-Mel spectral features and SCOT/PHAT joint weighting generalized cross correlation features are used for DOA estimation. The corresponding system is established and experimentally verified. Results show that the measured sound pressure sensitivity of the UW-FBG microphone is in the range of 0.1032-3.306 rad/Pa within the frequency range of 1000-3000 Hz, and the peak sound pressure sensitivity is about 3.306 rad/Pa. The estimated mean error of 2D DOA estimation is about 2.85°, and the error of 3D DOA estimation is about 5.465°. This method has good application prospects in distributed sound source localization.

Sensitivity-enhanced Fabry-Perot interferometric fiber-optic microphone using hollow cantilever.

Transducer components are crucial in optimizing the sensitivity of microphones. Cantilever structure is commonly used as a structural optimization technique. Here, we present a novel Fabry-Perot (F-P) interferometric fiber-optic microphone (FOM) using a hollow cantilever structure. The proposed hollow cantilever aims to reduce the effective mass and spring constant of the cantilever, thereby enhancing the sensitivity of the FOM. Experimental results demonstrate that the proposed structure outperforms the original cantilever design in terms of sensitivity. The sensitivity and minimum detectable acoustic pressure level (MDP) can reach 91.40 mV/Pa and 6.20 µPa/Hz at 1.7 kHz, respectively. Notably, the hollow cantilever provides an optimization framework for highly sensitive FOMs.

Performance enhancement of polyurethane foam applied to optical fiber microphones.

The application of polyurethane foam to optical fiber microphone sensitization is proposed. In this experiment, the Michelson interference system is used, and polyurethane foam is coated on the optical fiber of the signal arm. By changing the optical fiber material of the signal arm and the reference arm, four sets of comparative experiments are designed to test the sensitivity of the optical microphone. Through a scanning electron microscope (SEM) test and a pore size distribution test, the porous structure and non-closed cell structure characteristics, pore size range, etc., of the polyurethane foam were determined. The average sound absorption coefficient of the polyurethane foam is 0.66 through the sound absorption coefficient and sound insulation test. The sound absorption coefficient of each frequency band is above 0.2, the sound insulation is below 30 dB, and the overall sound insulation performance is poor, which can be regarded as an ideal sound absorption material. The sound-absorbing effect of polyurethane foam is better than that of nylon tight-packed materials in the frequency range of 500-2800 Hz, and it has a significant sensitization effect in this frequency band. In the frequency band above 2800 Hz, the sound-absorbing effect of nylon tight-packed optical fiber is better than that of polyurethane foam, and the optimal combination is determined by lateral comparison as signal arm (nylon tight-packed fiber + polyurethane foam) + reference arm (bare fiber). Finally, with different coating thicknesses as variables, the results show that the optical fiber microphone has the best sound collection effect when the coating thickness of polyurethane foam is 1.5 cm.

Simultaneous Primary Calibration on the Infrasonic Amplitude and Phase Sensitivities of Condenser Microphones and Comparison With Theoretical Results

Low frequency primary calibrations of condenser microphones are the basis of accurate measurement of low frequency sound and infrasound. Prior arts on the primary phase calibrations differ greatly, simultaneous primary amplitude and phase calibrations are rarely seen. Recently, two infrasonic sensitivity models of condenser microphones based on the pistonphone technique, for the vent immersed in sound field and outside are derived. The relevant models can explicitly characterize the influence of pistonphone, microphone and environment on the voltage output and sensitivity of the microphone. On this basis, simultaneous primary amplitude and phase calibration tests are evaluable. Based on adequate performance tests of the designed laser pistonphone, this paper carries out in-depth primary microphone calibrations. The calibrated infrasonic amplitude and phase sensitivities are in good agreement with theoretical results, thus proves their values to reveal and quantify the influence of various factors on the calibration results based on the pistonphone technique.

Acoustoelectric transducer based on electrokinetic phenomenon flow potential

A mathematical model of an acoustoelectric transducer based on the use of the electrokinetic phenomenon of the flow potential is proposed. It is shown theoretically that the flow potential increases in proportion to the strength of the constant electric pumping field, which is confirmed experimentally. The described converter has variable sensitivity. Rather large values of the sensitivity of an electrokinetic microphone have been obtained experimentally. The results of the work can be used in the design of acoustoelectric transducers. Keywords: Acoustoelectric conversion, Electrokinetic phenomena, Current potential, Flow potential hydrodynamics, Energy pumping. Electrokinetic microphone sensitivity.

Directional Response of a subcutaneous hearing implant microphone

• The directional response of a fully-implantable microphone was measured in various typical microphone positions on the head. • The microphone position on the mastoid tip showed the best broadband sensitivity to the front, best DI and best SII-DI. • The DI and SII-DI were negative in all microphone positions. • The highest microphone sensitivity was measured towards the backside of the head. • Noise sources in the direction of the microphone may have a negative impact on the speech intelligibility in noise.

Study on Optimal Position and Covering Pressure of Wearable Neck Microphone for Continuous Voice Monitoring.

Vocal cord disorder is one of the important health problems, especially in noisy industrial sites where excessive voice is required. A convenient and reliable communication method is required in a noisy environment to prevent the related disorders. However, the signal sensitivity of previous neck microphones is still insufficient to accurately convey the voice. In this study, we developed a skin-attachable neck microphone with a lightweight and flexible form factor. Also, we optimized the attachment position and covering pressure to maximize the signal sensitivity. As a result, we obtained the optimal position near the thyroid cartilage and confirmed that the signal sensitivity is the highest when the covering pressure is approximately 4 mmHg.Clinical Relevance- People can measure the voice status using a wearable neck microphone at the optimal position and covering pressure. It provides a solution to keep the vocal cords in good health even in a noisy environment.

In-vivo characterisation of an implanted microphone and totally implantable active middle ear implant

Objective To objectively evaluate acoustic sensitivity of the implanted microphone, and maximum stable gain of a totally implantable active middle ear implant. Design Prospective, single centre evaluation. Study sample Fourteen adult patients. Results Microphone sensitivity is approx. 10 dB lower than an externally worn conventional hearing aid, at frequencies up to 4000 Hz, and substantially lower at higher frequencies. The masking level due to microphone noise, which determines the softest test tones that can be detected, is estimated at <20 to <30 dB HL up to 1000 Hz, and <40 dB HL at higher frequencies. Maximum stable effective gain is the maximum amplification achievable without causing feedback whistling. In sensorineural hearing loss (SNHL) cases, it is 30–40 dB at frequencies up to 2000 Hz, allowing to compensate for even the maximum recommended hearing loss (60–70 dB HL). In both SNHL and mixed hearing loss (MHL) cases, maximum stable effective gain is lower (+20 to −30 dB) around 3000–6000 Hz. Conclusions Microphone sensitivity is high enough to achieve aided thresholds of 20–40 dB HL. A strong correlation between actuator coupling efficiency and maximum stable effective gain implies that any effort to improve actuator efficiency should also increase the available gain.

К ВОПРОСУ О ЧУВСТВИТЕЛЬНОСТИ МИКРОФОНА НОВОГО ТИПА

A new type of microphone is proposed, one of the distinguishing features of which is a variable sensitivity, which depends on the magnitude of the constant electric pumping voltage. In addition, a matching device (mediator) has been created that allows to significantly increase the sensitivity of the microphone. In the course of experiments, a significant increase in sensitivity was confirmed, both due to a charge pump and the use of a mediator. In the course of the experiments, the microphone sensitivity was obtained equal to 1990.5 mV / Pa at 1000 V pumping.

О СРАВНЕНИИ КОНДЕНСАТОРНОГО И ЭЛЕКТРОКИНЕТИЧЕСКОГО МИКРОФОНОВ

Basing on the analysis of the physical features of the operation of the microphone on electrokinetic phenomena, it has been experimentally confirmed that this microphone works on a functional principle different from the principle of operation of a condenser microphone. It is shown that a microphone based on electrokinetic phenomena can increase its sensitivity by up to about 40 dB due to pumping. Comparison of two experimental studies shows that the sensitivity of an electrokinetic microphone can strongly depend on the size of the porosity of the dielectric placed between the electrodes of the microphone.

Limitations of acoustic monitoring at wind turbines to evaluate fatality risk of bats

AbstractWind turbines (WTs) frequently kill bats worldwide. During environmental impact assessments, consultant ecologists often use automated ultrasonic detectors (AUDs) to estimate the activity and identity of bats in the zone of highest mortality risk at WTs in order to formulate mitigation schemes, such as increased curtailment speeds to prevent casualties. While acknowledging the potential of acoustic monitoring, we evaluate the limitations of AUDs for monitoring bats at WTs and highlight directions for future research. We show that geometric attenuation and atmospheric attenuation of ultrasonic echolocation calls, in conjunction with limited sensitivity of ultrasonic microphones, severely constrain detection distances of bats at WTs. Taking into account the acoustic shadow produced by the nacelle, AUDs cover only approximately 23% of the risk zone for a bat calling at 20 kHz and 4% for a bat calling at 40 kHz, assuming a 60 m blade length. This percentage will further decrease with increasing blade lengths in modern WTs. Additionally, the directionality of echolocation calls and the dynamic flight behaviour of bats constrain the detectability of bats. If a call can be detected, the low interspecific and high intraspecific variation of echolocation call characteristics may impair species identification, limiting the power to predict population‐level effects of fatalities. We conclude that technical, physical, and biological factors severely constrain acoustic monitoring in its current form. We suggest the use of several AUDs, installed at complementary sites at WTs, and the testing of other techniques, such as radar, cameras, and thermal imaging, to inform stakeholders on the mortality risk of bats at WTs.

The Role of Autosensitivity Control (ASC) in Cochlear Implant Recipients.

The purpose of the study was to examine the subjective and objective potential advantage for speech understanding in noise achieved by cochlear implant (CI) recipients when using the autosensitivity control (ASC) input signal processing in combination with the adaptive dynamic range optimization (ADRO). Eighteen subjects (8 females, 10 males, mean age 17.7 ± 6.7) were enrolled in a prospective open blinded comparative study between the ASC + ADRO condition vs. the ADRO alone; 16 were sequential binaural and 2 were monoaural CI recipients. All patients had been wearing their CI for at least 3 years, had no additional disabilities, had an age-appropriate receptive and expressive language. Word recognition performances in noise (at signal-to-noise ratio +5 dB HL) were significantly better in the ADRO-alone condition than in the ADRO + ASC condition. (p = 0.03) These objective outcomes were in agreement with the subjective reports. No significant difference was found in quiet. Our results, apparently in contrast with other reports in the literature, suggest that the decision of adding the slow-acting automatic reduction in microphone sensitivity provided by ASC should be limited to selected CI recipients.

Measuring implanted patient response to tone pips

BackgroundAn electrical potential not previously reported—electrical cochlear response (ECR)—observed only in implanted patients is described. Its amplitude and growth slope are a measurement of the stimulation achieved by a tone pip on the auditory nerve. The stimulation and recording system constructed for this purpose, the features of this potential obtained in a group of 43 children, and its possible clinical use are described. The ECR is obtained by averaging the EEG epochs acquired each time the cochlear implant (CI) processes a tone pip of known frequency and intensity when the patient is sleeping and using the CI in everyday mode. The ECR is sensitive to tone pip intensity level, microphone sensitivity, sound processor gain, dynamic range of electrical current, and responsiveness to electrical current of the auditory nerve portion involved with the electrode under test. It allows individual evaluation of intracochlear electrodes by choosing, one at the time, the central frequency of the electrode as the test tone pip frequency, so the ECR measurement due to a variable intensity tone pip allows to establish the suitability of the dynamic range of the electrode current.ResultsThere is a difference in ECR measurements when patients are grouped based on their auditory behavior. The ECR slope and amplitude for the Sensitive group is 0.2 μV/dBHL and 10 μV at 50 dBHL compared with 0.04 μV/dBHL and 3 μV at 50dBHL for the Inconsistent group. The clinical cases show that adjusting the dynamic range of current based on the ECR improved the patient’s auditory behavior.ConclusionsECR can be recorded regardless of the artifact due to the electromyographic activity of the patient and the functioning of the CI. Its amplitude and growth slope versus the intensity of the stimulus differs between electrodes. The relationship between minimum ECR detection intensity level and auditory threshold suggests the possibility of estimating patient auditory thresholds this way. ECR does not depend on the subject’s age, cooperation, or health status. It can be obtained at any time after implant surgery and the test procedure is the same regardless of device manufacturer.

Numerical study on the low frequency sensitivity variation of the microphone in laser-pistonphone based primary calibrations

The low frequency sensitivity of microphone is crucial for monitoring large-scale natural and artificial activities, but is acoustically controlled by the disturbing pressure leakage and heat conduction effects in its back-chamber. This issue has been partly studied by theoretical and experimental means, and is further studied here through numerical simulations on the laser-pistonphone based primary calibration of the microphone. Firstly, the frequency response of the calibrating sound-field, affected by the disturbing pressure leakage and heat conduction effects, is studied. Independent and coupling correction values for two effects are obtained based on the proposed model comparison method. Then, joint simulations on the primary calibration process are proposed for both the vent located in the calibrating sound-field and out. Simulation results verified previous studies, and more details about the parameter adjustment of both the pistonphone and microphone affecting the diaphragm deformation and sensitivity output of the microphone are elaborated here.