Forensic analysis of auditorily similar voices

ABSTRACT Purpose: to verify contributions of acoustic spectrographic analysis in the forensic identification of speakers with auditorily similar voices, considering the distinctive behavior of acoustic parameters: formants of vowel “é”, of connected speech, mean fundamental frequency in Hz, linear prediction curve of vowel “é” and linear prediction curve area; and to propose an objective method to use the analyzed parameters. Methods: a quantitative, qualitative and descriptive study, conducted in Pernambuco on 16 pairs of male siblings, aged 18-60 years. The subjects recorded videos from which the audios were extracted, numbered and sent to three examiners, in two groups: older brothers and younger brothers, for perceptual-auditory pairing. The correct pairings, indicated by at least two examiners, were submitted to acoustic analysis. The statistical tests included Wilcoxon, Kruskal-Wallis and Bonferroni, with p&lt;0.05. Results: the results of analyses of formants and the mean fundamental frequency were not enough to distinguish similar voices. Unprecedentedly, in the measurements of areas generated by the linear prediction curve graphs, a distinctive statistical significance was observed. Conclusion: it was concluded that, among the parameters studied, the measurements of areas of the linear prediction curve objectively indicated effectiveness in distinguishing speakers with auditorily similar voices.摘要 目的：验证声学频谱分析（acoustic spectrographic analysis）在听觉相似嗓音说话者法医同一认定中的应用贡献，同时考量各声学参数的特异性表现：元音“é”的共振峰（formants）、连续语音、以赫兹（Hz）为单位的平均基频（fundamental frequency）、元音“é”的线性预测曲线（linear prediction curve）以及线性预测曲线面积；并提出一套可依托上述分析参数的客观鉴定方法。 方法：本研究为定量、定性与描述性研究，于巴西伯南布哥州开展，共招募16对年龄介于18~60岁的男性同胞作为受试对象。受试者录制视频后从中提取音频，将音频编号并分为两组——兄长组与弟弟组，交由3名鉴定人员开展感知听觉配对甄别。经至少2名鉴定人员确认的正确配对样本，将进入声学分析流程。本研究采用的统计检验方法包括威尔科克森检验（Wilcoxon）、克鲁斯卡尔-沃利斯检验（Kruskal-Wallis）与邦费罗尼校正检验（Bonferroni），检验显著性水准设定为p<0.05。 结果：共振峰与平均基频的分析结果无法有效区分听觉相似的嗓音。本研究首次观测到，在线性预测曲线图形生成的面积测量中，呈现出具有统计学意义的区分效果。 结论：综合本次研究考察的各项参数，线性预测曲线面积测量可客观且有效地实现听觉相似嗓音说话者的区分鉴定。