The effects of speaker individuality on voice disguise and speaker recognition in application to forensic speech science

人类的声音被广泛认为是身份的重要标志，将一个人固定在他们的身体上。个人声音的假设独特性是法医言语科学研究的基础，这是一个致力于在刑事调查中使用声音证据的应用言语科学领域。典型的法医案例包括确定两个录音是否可能来自同一个说话者，或者它们是否可能由不同的说话者产生（诺兰，1991）。对这项任务提出重大挑战的一个领域是声音伪装，即一个人有目的地修改他们的声音，以便听起来像其他人，从而逃避识别。这在检测身份欺诈案件的背景下尤其重要（特别是在银行和其他大型组织实施语音识别技术的当前环境下），过去一年欺诈案件总数增加了15%（国家统计局，2019年）。令人担忧的是，过去的研究发现，有些人可以高度准确地模仿他人的讲话（Leemann & Kolly，2015）。尽管如此，迄今为止的研究还没有全面解决语音伪装的精确机制，以及即使是最好的伪装是否包含可以识别说话者的特征。因此，很难就伪装的声音是否可能是嫌疑人提供一个强有力的结论，因为必须提出来自语音信号的具体证据，才能在法庭上证明这种说法是正确的。

The human voice is widely viewed as an important marker of identity, anchoring an individual to their body. The hypothesised uniqueness of individual voices lies at the foundation of research in forensic speech science, which is an area of applied speech science dedicated to the use of voice evidence in criminal investigations. Typical forensic casework involves establishing whether or not two voice recordings are likely to be from the same speaker, or whether they could have been produced by different speakers (Nolan, 1991). One area that provides a significant challenge to this task is vocal disguise, whereby an individual has purposefully modified their voice in order to sound like somebody else and, therefore, evade identification. This is particularly relevant in the context of3detecting instances of identity fraud (especially in the current climate of voice identification technologies implemented by banks and other large organisations), with an increase of 15% in the past year of overall fraud cases (Office of National Statistics, 2019). Worryingly, past research has found that some individuals can imitate the speech of others to a high degree of accuracy (Leemann & Kolly, 2015). Despite this, research to date has not comprehensively addressed the precise mechanisms of voice disguise and whether even the best disguises contain features that could identify the speaker. As a consequence, it can be extremely difficult to provide a robust conclusion on whether a disguised voice is likely to be the suspect or not, as specific evidence from the speech signal must be presented in order to justify such claims in court.