Voice quality is an important component of effective communication in call center conversations. A qualitative research methodology was used in the present study to examine how Filipino customer service representatives (CSRs) and American customers use voice quality features in call center discourse. A precise evaluation of voice quality features can aid in the development of effective communication strategies. Through interrater agreement, the present study aimed to validate the reliability of voice quality feature assessment. In this study, how Filipino CSRs and American customers’ call center telephone conversations differed in terms of voice quality characteristics such as volume (Loud/Soft), pitch (High/Low), tension (Tense/Lax), and rhythm (Fast/Slow) was investigated. The conversation transcripts were examined using the aforementioned voice quality features. The transcriptions were then evaluated by three independent raters to determine interrater agreement. The findings revealed a high level of interrater agreement between the three raters of all voice quality features, with up to 0.8 in identifying voice quality changes in generic stages. In particular, a higher agreement was found in the assessment of specific voice quality features such as loudness, high pitch, and tension. Praat software was also used to aid in the analysis of some voice recordings to validate the interrater agreement reliability. The approach taken in the present study for assessing voice quality using interrater agreement and Praat software can improve service quality in the call center industry and provides a reliable and valid framework for future qualitative research in applied linguistics.