Multiphysics Modeling and Material Selection Methods to Develop Optimal Piezoelectric Plate Actuators for Active Noise Cancellation

The performance of a piezoelectric actuator for active noise cancellation depends primarily on the quality of the actuator material and its design approach, i.e., single-layer or multi-layer actuators, stacks, benders, or amplified actuators. In this paper, material selection and multiphysics modeling were performed to develop an optimal piezoelectric plate actuator for active noise cancellation. The material selection process was analyzed using two multi-criteria decision making (MCDM) approaches for material selection, i.e., figure of merit (FOM) for actuators and the technique for order of performance by similarity to ideal solution (TOPSIS). Of the 12 state-of-the-art piezoelectric actuator materials considered in this article, PMN–28% PT is the best material according to TOPSIS analysis, while (PIN24%-PMN-PT) is the best material according to FOM analysis. The ranking of state-of-the-art piezoelectric material categories for actuators according to the two analysis is consistent and the category of monocrystalline piezoelectric materials has the highest actuation performance. The multiphysics modeling was performed using ANSYS Mechanical using two different approaches: one using Ansys Parametric Design Language (APDL) command fragments, the other installing the PiezoAndMEMS ACT extension in ANSYS. Static structure, modal, and harmonic response analyses were performed to determine an optimal pair of piezoelectric plates to be used as an actuator for active noise cancellation. A pair of plates of the same materials, but of different dimensions turns out to be the optimal piezoelectric plate actuator for active noise reduction, according to the two multiphysics modeling methods.

Noise Attenuation Effects on Speech Recognition of Cochlear Implant Users Inside Helicopters

BACKGROUND: The speech recognition levels of cochlear implant (CI) users are still incompatible with ICAO hearing requirements for civil aviation pilots testing in the noisy background condition of the helicopter cockpit. In this study, we evaluated noise attenuation effects on speech recognition in the same background condition.METHODS: The study involved the evaluation of 12 Portuguese-speaking CI users with post-lingual deafness and with a pure tone average up to 35 dB HL between 500 and 2000 Hz and up to 50 dB at 3000 Hz on at least one of the ears, and of three normal hearing pilots (controls). We performed speech recognition tests using sentences, numbers, and disyllables for all participants through the VHF radio. The assessment took place inside a helicopter with engine on, using three setups: 1) with headset without the active noise cancellation; 2) activating the noise cancellation system of the headset itself; and 3) connecting the speech processor directly to the helicopter radio system.RESULTS: The headset active noise-cancellation improved only the recognition of sentences. The direct connection system compared to the headset without anti-noise attenuation significantly improved all the recognition tests. The median for numbers was 90%, but the best score for disyllables recognition was 56%.DISCUSSION: The noise attenuation resources proposed in this study improved the CI users speech recognition when exposed to the noisy helicopter cockpit. However, speech recognition of CI users still did not meet the standards of ICAO, which requires at least 80% for understanding disyllables in the speech in noise test.Caldeira JMA, Goffi-Gomez MVS, Imamura R, Bento RF. Noise attenuation effects on speech recognition of cochlear implant users inside helicopters. Aerosp Med Hum Perform. 2021; 92(11):880-885.

Regularized spherical harmonics-domain spatial active noise cancellation in a reverberant room

Active Noise Cancellation (ANC) at a target area in an open space, as opposed to cancellation in the ears through headphones, can lead to future applications. For instance, a personal acoustic environment in an airplane seat or inside a car, or a quiet zone in a noisy shared workspace can be possible using such open-space ANC without any uncomfortable on-body audio equipment. Recent advancements reinforce the practicality of such systems. However, regularization of the cancellation signal has been a crucial challenge in open-space ANC as it causes amplification of noise at locations away from the target area. This work presents a spherical harmonics-domain feed-forward spatial ANC method with a room-wide global cost function to address this issue. This room-wide global cost function is used for optimizing the set of regularization hyperparameters, while at run time only local information captured by a microphone array surrounding the target listening zone is required. Numerical experiments applying the proposed method in a simulated reverberant room show the effectiveness of the proposed method in creating a specific zone of silence with low to moderate noise amplification in the rest of the room.