Conducting smartphone surveys offers flexibility in collecting various types of responses. Among these various response modalities, voice responses stand out for their potential to facilitate deeper respondent engagement and expression. However, high item-nonresponse rates pose significant challenges to their large-scale use. Therefore, the objective of this study is to better understand whether and to what extent socio-demographic characteristics, technological skills, and survey-related aspects are associated with item-nonresponse. Our preliminary findings suggest that certain socio-demographic groups, including males and respondents with low to medium levels of education, as well as younger respondents (aged 19 to 30 years), exhibit lower item-nonresponse rates. Additionally, respondents with good smartphone skills and those expressing high levels of interest in the survey show lower rates of item-nonresponse. This similarly applies to respondents perceiving the survey as being easy, not long, and not intimate.