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Phonetic manifestations of voice disguise
Růžičková, Alžběta ; Skarnitzl, Radek (advisor) ; Šturm, Pavel (referee)
In forensic practice, when there is the need to identify a speaker using a recording of his speech, forensic voice identification is applied. If the perpetrator is aware of the option of their speech being recorded, for instance in cases such as abduction or blackmail, they can attempt voice disguise in order to thwart voice identification process. This thesis surveys strategies used by Czech speakers, when they attempt to disguise their voices using any means of their choice. Auditory analysis of 80 speakers' disguised voices was performed. 15 of them, who used more complex strategies for disguising their voices, acoustic analysis of fundamental frequency, formant values and speech and articulatory rate was performed. For those speakers, perceptual tests were carried out, to examine the degree of difficulty in uncovering modifications of one's speech and the effect of the used disguise strategies on speaker identifiability in a voice line-up.
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