Preliminary F0 statistics and forensic phonetics
Jonas Lindh · 2006
Fundamental frequency has been used for a long time in speaker identification (Braun, 1995; Rose, 2003). The within-speaker variation in F0 is affected by several factors. In Braun (1995), they are categorized as technical, physiological and psychological factors. Tape speed, which surprisingly still is an issue for forensic samples, and sample size are examples of technical factors. Smoking and age are examples of physiological factors, while emotional state and background noise are examples of psychological factors. However, fundamental frequency has been shown to be a successful forensic phonetic parameter (Nolan, 1983). To be able to study differences it is suggested to use long-term distribution measures such as arithmetical mean and standard deviation (Rose, 2002). The duration of the samples should be more than 60 seconds according to Nolan (1983), but Rose (1991) reports that F0 measurements for seven Chinese speakers stabilized much earlier, implying that the values may be language specific (Rose, 2002). Positive skewing of the F0 distribution for a speaker is typical (Jassem et al., 1973). When extracting fundamental frequency information for 109 young male Swedish speakers, it was discovered that octave jumps and other analysis errors were frequent. Manual examination of the results revealed that using median values instead of means was more reliable as it is less sensitive to