ASSESSMENT OF LOUDNESS PERCEPTION IN MICE

In the human audiogram, hearing thresholds depend on sound frequency. Similarly, the subjective perception of sound loudness is frequency-dependent, such that a 20 dB sound at 1 kHz can be perceived as equally intense as an 80 dB sound at 20 Hz. In hyperacusis, the perceived loudness of a sound is disproportionately higher than its physical intensity, rendering otherwise normal intensity sounds uncomfortable. Studying hyperacusis in animal models has proven challenging, as assessing hearing discomfort in animals is difficult. While auditory thresholds can be readily measured in mice, measures of hearing discomfort, and thus loudness perception curves, have not yet been established. Here, we demonstrate that hearing discomfort in mice can be assessed using behavioral measures with no conditioning, enabling the construction of frequency-dependent loudness curves. In passive exposure experiments, mice spent less time adjacent to a sound source when they perceived the sound as louder. By exposing mice to sounds of varying intensities and frequencies, and measuring the mean time spent near the sound source, we established perceived loudness curves across frequencies in a C57BL/6 cohort. We further assessed the relationship between these loudness curves and auditory thresholds using auditory brainstem responses. Our results establish a baseline for frequency and intensity dependent loudness perception in mice. Time spent near the sound source emerges as a robust and repeatable measure of hearing discomfort without task learning. We anticipate that this paradigm will serve as a foundation for future studies investigating hyperacusis-related behaviors in mouse models.