Designs, Experiments, and Applications of Multichannel Structures for Hearing Aids

The structures of common multichannel processing for hearing aids include equal bandwidth (BW) finite impulse response (FIR) filter bank, nonuniform BW FIR filter bank, and fast Fourier transform (FFT) plus inverse FFT (IFFT). This paper analyzes their operation principles, indicates the design methods by means of MATLAB R2018b resources, and describes the main characteristics: synthetical ripple, bank filters’ group delays, and individual filter sidelobe attenuation. Three schemes are proposed: equal BW sixteen-filter bank, logarithmic BW eight-filter bank, and 128-point FFT plus IFFT with overlap-add operation. To build the experimental modules, we introduce the settings of spectrum scopes, the acquirement of realistic speech and noises, and the gain enhancing/reducing needs of hearing aid features; the characteristics of synthetical outputs confirm precise control ability of the multichannel modules and differences between the three schemes. Subsequently, this paper illustrates two applications of the multichannel structures in hearing aids, the equal BW sixteen-filter bank with spectral subtraction (SS) for an artificial intelligence (AI) noise reduction (NR) and 128-point FFT plus IFFT spectral distortion removal for a directional microphone (DM). In Amy’s speech mixed with ringing, milk steamer, and strong wind noises separately, the SS processor improves signal-noise-ratio (SNR) by 6.5 to 15.9 dB. By measuring waveforms and spectra at the DM input and output, the DM system seamlessly removes the spectral distortion.

Increasing the Effectiveness of Hearing Aid Directional Microphones

Directionality is the only hearing aid technology — in addition to amplification — proven to help hearing aid users hear better in noise. Hearing aid directionality has been documented to improve speech intelligibility in multiple laboratory studies. In contrast, real-world studies have shown a disconnect between the potential of the technology and what hearing aid users experience in their daily life. This article describes the real-world studies that inspired ReSound to take a different approach to applying directional microphone technology. This approach is based on the idea that hearing aid directionality can leverage natural binaural hearing and inherent listening strategies. The directional strategy includes three listening modes that will be explained. These are the Spatial Cue Preservation mode, the Binaural Listening mode, and the Speech Intelligibility mode. The strategy and the advantages it provides in terms of sound quality, spatial hearing, and improved signal-to-noise ratio with maintained awareness of surroundings are explained.

Coupled D33 Mode-Based High Performing Bio-Inspired Piezoelectric MEMS Directional Microphone

Microelectromechanical system (MEMS) directional microphones have been identified as having use in multi-projected virtual reality applications such as virtual meetings for projecting cameras. In these applications, the acoustic sensitivity plays a vital role as it biases the directional sensing, signal-to-noise ratio (SNR) and self-noise. The acoustic sensitivity is the multiplied outcome of the mechanical sensitivity and the electrical sensitivity. As the dimensions are limited in MEMS technology, the improvement of the acoustic sensitivity by reflecting the mechanical as well as electrical domains is a challenge. This paper reports on a new formation of the D33 mode, the coupled D33 mode, based on piezoelectric sensing to improve the acoustic functionalities. The unique advancement of the proposed D33 mode is that it allows multiple spans of the regular D33 mode to perform together, despite this increasing the diaphragm’s dimensions. At a reduced diaphragm size, the orientation of the coupled D33 mode realizes the maximum conversion of the mechanical deflection into electrical sensitivity. The significance of the proposed D33 mode in comparison to the regular D33 mode is simulated using COMSOL Multiphysics. Then, for a proof–of–concept, the experimental validation is carried out using a piezoelectric MEMS directional microphone inspired by the ears of the fly Ormia ochracea. In both ways, the results are found to be substantially improved in comparison with the regular approach of the D33 mode, showing the novelty of this work.

Contactless diagnostics of the technical state of the valve mechanism of the internal combustion engine

The aim of the study is to analyze the possibilities of developing a contactless diagnostics system of the technical state of the valve mechanism, which excludes mounting sensors on the body of the diagnosed equipment, by using a directional microphone as a sensitive element. In order to test the proposed hypothesis, a directional microphone designed to measure the level of acoustic noise, sound pressure level and to obtain amplitude-frequency characteristics in the range of 10-10 kHz has been used. In the work, an experimental determination of the spectrum of the valve mechanism acoustic vibration and its comparison with the spectrum obtained from an accelerometer has been carried out; the principle of building an automated diagnostic system using a directional microphone has been formulated.