Toward accessible hearing care: A systematic review of low-cost portable otoacoustic emission devices and measurement advances.

Otoacoustic emissions (OAEs) are essential for non-invasive assessment of cochlear function but remain inaccessible in many low-resource settings because conventional systems are expensive, insufficiently portable, and largely supplied through proprietary platforms from a limited number of manufacturers. This systematic review characterized portable and low-cost OAE systems, focusing on their hardware architectures, measurement platforms, OAE modalities, performance, and technical or clinical validation. Studies directly evaluating portable, low-cost, mobile, smartphone-integrated, or consumer-grade OAE systems were eligible. IEEE Xplore, PubMed, and the ACM Digital Library were searched through 24 November 2025, identifying 1551 records. Risk of bias in studies reporting diagnostic accuracy was assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool and findings were synthesized narratively because of methodological and outcome heterogeneity. Seven studies met the eligibility criteria and evaluated smartphone-connected probes, wireless earbuds, single-transducer prototypes, and other portable platforms. Three studies assessing diagnostic classification against clinical hearing-status information reported sensitivities of 100% and specificities of 88.0%-89.7%, while several systems were supported only by small feasibility studies, normal-hearing samples, simulations, or artificial-ear testing and lacked independent clinical diagnostic validation. Portable and low-cost OAE technologies show promise for expanding access to cochlear assessment; however, standardized calibration and noise characterization, larger clinical studies, and validation against appropriate reference standards are required before they can serve as reliable alternatives to established clinical systems. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 framework and was prospectively registered in the International Prospective Register of Systematic Reviews (PROSPERO; CRD420251250576). This work was supported by the Ralph W. and Grace M. Showalter Research Trust (No. 41001449), the Clifford B. Kinley Trust, and Purdue University's Health of the Forces initiative.