Evaluating the Audible Contrast Threshold test as a language-independent tool for assessing speech perception with hearing protection devices

Hearing protection devices (HPDs), such as earplugs and earmuffs, are essential for reducing the risk of noise-induced hearing loss; however, they also attenuate speech signals and may hinder communication in noisy environments. While HPD performance is typically assessed using attenuation-based metrics such as the Noise Reduction Rating (NRR), these do not account for speech perception. Including speech perception assessments in fit-testing protocols could enhance evaluation of real-world performance. The Audible Contrast Threshold (ACT) is an adaptive, language-independent hearing-in-noise test used by audiologists to estimate the contrast-level ratio required to detect spectro-temporal modulation (STM) against static noise. The test involves identifying modulated target stimuli among unmodulated reference stimuli (noise). The ACT reflects the minimum STM a person can detect, which is proposed to correlate with the ability to understand speech in background noise. The presented work will demonstrate findings from a comparative pilot study examining ACT performance alongside a widely used adaptive hearing-in-noise test, under hearing protection conditions. The discussion will include methodological considerations, practical implementation, and the potential benefits of integrating ACT into HPD fit-testing protocols, particularly in military and multilingual settings where language-neutral evaluation is advantageous and reduced listening effort is desired.