The Effect of Telephone Transmission on Voice Quality Perception

This study aims to analyze the effect of telephone transmission on the voice quality perception of subjects with dysphonia and seeks to contribute to the use of perceptual voice analysis in forensic context. The main hypothesis is that the auditory perception of voice quality differs according to the acoustic quality of the speech material.

Eight male speakers were simultaneously recorded directly by a digital recorder and over a mobile phone.

A perceptual experiment containing 21 speech samples was used. The samples were analyzed via an online adaptation of the Vocal Profile Analysis Scheme (VPAS) into Brazilian Portuguese by a group of six voice-specialized professionals. Data analysis included the relative frequency of the 10 most evaluated VPAS settings in both recording conditions, and the relative frequency of the VPAS groups of features. A multidimensional scaling technique was applied to investigate the perceptual distance between stimuli pairs from both recording conditions. This was followed by a nonparametric multiple linear regression analysis that aimed to comprehend the underlying variables that motivated the spatial arrangement of the stimuli.

The telephone transmission effect may have an influence on assessing correctly the supralaryngeal, laryngeal, prosodic, and temporal VPAS settings. The perceptual distance between stimuli pairs were mainly motivated by the rating of velopharyngeal system, respiratory support, laryngeal tension, speech rate, and creaky voice.

The auditory perception differences between the stimuli pairs with different acoustic qualities could be related to the mobile phone bandwidth and data compression, and to telephone interaction characteristics. A group of laryngeal, supralaryngeal, temporal, and respiratory settings was mainly related to the dissimilarities reported. In terms of the application of VPAS in forensic context, the protocol was considered a relevant scientific tool that enables standardizing and analysis comparison among different groups of forensic specialists.