A workflow and digital filters for correcting speed and equalization errors on digitized audio open-reel magnetic tapes

This paper presents a workflow and digital filters for compensating speed and equalization errors that can impact digitized audio open-reel tapes. Thirty cases of mismatch between recording and reproducing speed (3.75, 7.5, 15, and 30 in/s) and equalization standards [National Association of Broadcasters (NAB), Consultative Committee for International Radio (CCIR) and Audio Engineering Society) were considered. For three frequent cases of mismatch (NAB 3.75 in/s-CCIR 7.5 in/s; NAB 3.75 in/s-CCIR 15 in/s; and NAB 7.5 in/s-CCIR 15 in/s) Multiple Stimuli with Hidden Reference and Anchor-inspired tests with ≥21 participants assessed the workflow and digital filters. using excerpts of music and voice. Two different corection filters were used, both of which provided promising results. Following this subsequent analyses examined predictive variables for correct and incorrect Multiple Stimuli with Hidden Reference and Anchor performance, as well as spectral and numerical differences between filters, which provide key insights and recommendations for further related work.