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Objective Quality and Intelligibility Measures
Published in Philipos C. Loizou, Speech Enhancement, 2013
A series of studies [82] were published validating the AI culminating with the creation of the ANSI S3.5-1969 standard [69]. These studies investigated among other things the impact of low-pass, high-pass, and bandpass filtering of speech in various noise masking conditions [82]. The standard was later revised in 1997. In the ANSI S3.5-1997 standard [70], the name of the measure changed from AI to SII. The computation of the audibility function (SNR) was modified to take into account the effects of spread of masking and vocal effort. Masking becomes an issue when higher energy vowels make lower energy consonants inaudible. The revised standard takes into consideration the fact that SI can decrease at extremely high sound pressure levels, something known as “roll-over” effect [68,83]. In the presence of high background noise levels, a talker is likely to raise the voice level (vocal effort) due to the Lombard effect. Increased vocal effort is associated with variation in the amplitude spectrum causing possible changes to intelligibility. The audibility function was also modified in the revised standard to accommodate individuals with conductive hearing loss. Hearing threshold levels may be used as additional input to the SII computation.
A study of human vocal effort in response to the architectural auditory environment
Published in Architectural Science Review, 2020
Pantea Alambeigi, Jane Burry, Sipei Zhao, Eva Cheng
Since the main aims of this study are to objectively quantify and subjectively self-express the vocal effort in two different acoustic environments, measuring speech pressure level during the experiment was performed for each participant in both spaces. The procedure with the following described instrumentation was repeated 40 times, twice per subject, each lasting for two minutes’ duration.