On the use of the TIMIT, QuickSIN, NU-6, and other widely used bandlimited speech materials for speech perception experiments

The use of spectrally degraded speech signals deprives listeners of acoustic information that is useful for speech perception. Several popular speech corpora, recorded decades ago, have spectral degradations, including limited extended high-frequency (EHF) (>8 kHz) content. Although frequency content above 8 kHz is often assumed to play little or no role in speech perception, recent research suggests that EHF content in speech can have a significant beneficial impact on speech perception under a wide range of natural listening conditions. This paper provides an analysis of the spectral content of popular speech corpora used for speech perception research to highlight the potential shortcomings of using bandlimited speech materials. Two corpora analyzed here, the TIMIT and NU-6, have substantial low-frequency spectral degradation (<500 Hz) in addition to EHF degradation. We provide an overview of the phenomena potentially missed by using bandlimited speech signals, and the factors to consider when selecting stimuli that are sensitive to these effects.