An Experiment on Voice Identification by Visual Inspection of Spectrograms
Oscar Tosi, Herbert Oyer, Charles Pedrey, Brad Lashbrook, J. Nicol · The Journal of the Acoustical Society of America · 1971
An experiment aimed to test Kersta's claims on the reliability of speaker identification by visual inspection of spectrograms is being performed under a contract with the Michigan State Police, sponsored by the Federal Department of Justice. Thirty-eight examiners were selected, trained during approximately three weeks, and then employed to perform a total of approximately 32 000 trials of identification. Two hundred and fifty speakers, taken randomly from a homogeneous male student population of 25 000 twice recorded, one month apart, five utterances of nine clue words, spoken in three different conditions. Approximately 54 000 spectrograms (broad-band, 4-kHz, Voiceprint spectrograph) were obtained from these recordings and used in the trials of identification performed by the examiners. One-third of these trials were closed, one-third were open, including a matching spectrogram, and one-third were open trials not including a matching spectrogram. Several levels were tested in this experiment, involving 648 possible combinations, each combination defining a different type of trial. Each type of trial was repeated four times, by 18 examiners grouped into three panels and nine subpanels. The levels tested were: number of clue words (2 levels); number of utterances of each clue word (3 levels); phonetic boundaries of the clue words (3 levels); levels of transmission (3 levels); class of spectrograms (2 levels, contemporary and noncontemporary); number of known speakers (3 levels); and type of trials (3 levels). After the completion of this experiment, the data is analyzed through a computer.