A novel microelectromechanical piezoelectric concentrated-mass bulk acoustic wave (BAW) resonator based on out-of-plane degenerate mode is proposed for detecting micro angles. A PZT resonator with a concentrated-mass is designed to enhance the driving and sensing efficiency. The device combines the bulk acoustic wave drive/sense with a rocking concentrated mass to increase the resonant frequency, the signal quality and the resolution of the sensor. A 10 × 10 mm device has been fabricated and assembled by the microelectromechanical system process and the traditional mechanical process. The test results measured by the impedance analyser in air show that the resonant frequency and the quality factor of this device are about 174 kHz and 110, respectively. Moreover, the frequency split is only about 200Hz without any tuning methods.

The series resistance method (SRM) is introduced to obtain an equivalent circuit of a piezoelectric micro resonator. This method uses two series resistances respectively connected to driving electrodes of the resonator, and then detects the voltage amplitudes at the terminals of the series resistances and phase difference between them. Compared with the results of the impedance analyser, the deviations of resonance frequency, motional capacitance (C 1 ), motional inductance (L 1 ) of the SRM are 0.213%, 7.48%, and 7.62%, respectively. The SRM is easy to be realised in the laboratory. To a certain extent, it can replace the impedance analyser to attain the equivalent parameters of the piezoelectric micro resonator.

The purpose of the study was to investigate the effect of the surgical masks and N95 masks on the acoustic and aerodynamic parameters of voice assessment during the coronavirus disease 2019 pandemic. The challenge of the study was to enable each inexperienced participant to perform a number of acoustic and aerodynamic voice assessment in a qualified and homogeneous manner without and with medical masks, and to minimize the individual differences. There were 32 healthy participants recruited in the study, including 16 males and 16 females. The acoustic parameters analyzed included fundamental frequency, standard deviation of fundamental frequency (fundamental frequency standard deviation), percentage of jitter (%), percentage of shimmer (%), glottal-to-noise excitation ratio (GNE), and the parameters of irregularity, noise and overall severity. The aerodynamic parameters included s time, z time, s/z ratio and maximum phonation time. When wearing surgical masks, the GNE ratio (P = .043) significantly increased, whereas noise (P = .039) and s time (P = .018) significantly decreased. When wearing N95 masks, the percentage of shimmer (P = .049), s time (P = .037) and s/z ratio (P = .048) significantly decrease. In general, performing voice assessment with a medical mask proved to be reliable for most of the acoustic and aerodynamic parameters. It is worth noting that the shimmer (%), could be slightly impacted when wearing N95 masks. Wearing surgical masks might slightly influence the measurement of noise and higher GNE ratio. The s/z ratio could be affected when wearing N95 masks. The contribution of the study is to explore acoustic and aerodynamic parameters that might be easily affected by wearing masks during the voice assessment, and provide references for clinical evaluation of voice disorders during the pandemic of coronavirus disease 2019.