Performance Evaluation Framework for Contact Microphones: A Controlled Laboratory Study for Voice Research

Low-cost tools for voice monitoring are increasingly important in clinical and occupational settings, particularly where traditional air microphones are limited by ambient noise or hardware constraints. Accelerometer calibration commonly relies on shaker-plate systems that provide controlled, repeatable excitation; however, comparable procedures for contact microphones (CMs) are lacking. This study introduces a standardized shaker platform (SSP), a laboratory framework designed to evaluate and compare the vibratory performance of CMs under regulated excitation conditions.

Laboratory-based experimental design.

As proof of concept, the framework was applied to six commercially available low-cost CMs to demonstrate its analytic sensitivity and reproducibility. CMs were evaluated under identical conditions using a broadband logarithmic sweep (50 Hz-3 kHz) delivered through a custom steel-plate SSP. A calibrated accelerometer provided a reference for normalization across devices. Signal-to-noise ratio (SNR), spectral sensitivity, and response flatness were computed using standardized MATLAB routines.

The SSP demonstrated high repeatability across all tested devices under controlled mechanical excitation. Using this framework's stability and analytic sensitivity, all devices tested showed optimal sensitivity within the voice fundamental frequency range (80-300 Hz) and first harmonic region (300-1000 Hz), though spectral sensitivity varied substantially across the full bandwidth (-5.5 dB to +17.0 dB relative to reference), reflecting expected piezoelectric sensor characteristics. Further, distinct spectral and SNR patterns were captured for each CM, illustrating the system's ability to resolve fine performance differences under identical excitation conditions.

This proof-of-concept study demonstrates a standardized laboratory framework for quantitative CM evaluation under controlled mechanical excitation. The SSP provides a low-cost, reproducible alternative to conventional shaker rigs, enabling systematic cross-sensor benchmarking and supporting future research and clinical translation of affordable vibratory sensing tools.