High-fidelity earplugs are generally assumed to preserve the musical characteristics of attenuated sound reaching the eardrums better than general-purpose earplugs by having flatter spectral attenuation (or insertion loss) characteristics. However, as all earplugs display non-flat insertion loss characteristics, quantifying and comparing spectral distortion magnitude is non-trivial: a simple calculation of flatness doesn’t capture information about the relevance to musical perception of the different types of spectral distortions. In this paper, a method is proposed that compares earplug spectral distortion by their effects on commonly used spectral measures of timbre on a collection of audio files: centroid, spread, skewness, kurtosis, flatness, and brightness. This musical spectral distortion score is shown to have very little correlation to a simple metric evaluating insertion loss flatness, and moderate correlation to simple average insertion loss in decibels, while also showing that the a foam earplug is more distorting than any of the musician earplugs.
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