The most common voice disorders are chronic or recurring conditions that are likely to result from faulty and/or abusive vocal behavior patterns. Such behaviorally based disorders are difficult to accurately assess, and effectively rehabilitate, because of a lack of capability to perform long-term monitoring and provide meaningful feedback outside of the clinical voice-therapy situation. To address this need, we propose to develop an ambulatory monitoring and feedback system for evaluating and treating voice disorders that can: (1) reliably and unobtrusively provide long-term, continuous tracking of important parameters of vocal function, and (2) provide feedback to the user when voice parameters exceed 'safe' limits and/or target phonatory behaviors are not maintained. The proposed project will focus on further developing an already existing prototype instrument, referred to as the Portable Vocal Accumulator (PVA), into a clinically useful system by following two parallel, related lines of development. One aim will be to initiate group-based clinical trials of the PVA to: (a) develop sampling strategies for reliably estimating "typical" voice use for future clinical and research applications; (b) determine mechanical reliability and subject tolerance of the device; (c) assess the ability of the device to reliably track vocal function in patients with common voice disorders; (d) begin to evaluate the clinical validity of ambulatory monitoring of voice use with the PVA device by comparing results between normal and voice-disordered groups. The second main aim is to implement and test new features, including: (a) improved biofeedback capabilities, (b) a software interface that will improve data downloading and interpretation for clinicians; (c) development of digital signal processing algorithms to extract additional relevant information from the accelerometer signal. In the long-term, clinical use of the PVA is expected to improve the diagnosis and treatment of the most common types of voice disorders in which the identification of harmful patterns of voice use and/or compliance with vocal retraining regimens are considered critical elements to effective management. It is also expected that the PVA will provide unprecedented research capability to directly investigate and test basic theories about the etiology and treatment of many common voice disorders.