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The Average Direct Current Offset Values for Small Digital Audio Recorders in an Acoustically Consistent Environment
Author(s) -
Koenig Bruce E.,
Lacey Douglas S.
Publication year - 2014
Publication title -
journal of forensic sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.715
H-Index - 96
eISSN - 1556-4029
pISSN - 0022-1198
DOI - 10.1111/1556-4029.12452
Subject(s) - microphone , standard deviation , offset (computer science) , digital audio , acoustics , sound recording and reproduction , dc bias , computer science , mathematics , speech recognition , physics , sound pressure , audio signal , statistics , electrical engineering , engineering , voltage , speech coding , programming language
In this research project, nine small digital audio recorders were tested using five sets of 30‐min recordings at all available recording modes, with consistent audio material, identical source and microphone locations, and identical acoustic environments. The averaged direct current ( DC ) offset values and standard deviations were measured for 30‐sec and 1‐, 2‐, 3‐, 6‐, 10‐, 15‐, and 30‐min segments. The research found an inverse association between segment lengths and the standard deviation values and that lengths beyond 30 min may not meaningfully reduce the standard deviation values. This research supports previous studies indicating that measured averaged DC offsets should only be used for exclusionary purposes in authenticity analyses and exhibit consistent values when the general acoustic environment and microphone/recorder configurations were held constant. Measured average DC offset values from exemplar recorders may not be directly comparable to those of submitted digital audio recordings without exactly duplicating the acoustic environment and microphone/recorder configurations.