The purpose of this study was to explore whether significant differences existed in mean amplitude and total phonation time between a group of older individuals with idiopathic Parkinson's disease (PD) and an age-and gender-matched control group (NO PD) in their natural environments, based on data collected by the ambulatory phonation monitor (APM; KayPENTAX). Method: In this prospective, between-groups study, 5 individuals with PD and 5 NO PD controls wore the APM on 3 typical 8-hr days. The dependent variables included mean amplitude and total phonation time as measured by the APM. All of the participants also completed a self-estimated talk time log and an APMuse questionnaire. Data analysis included descriptive P