The use and role of the Ambulatory Phonation Monitor (APM) in voice assessment.

Vocal load plays a significant role in the aetiology of voice disorders and influences the response to treatment. For this reason, many researchers have focused their attention on how a voice is used, especially when vocal load is increased, during working hours for instance. The majority of studies in this regard have been performed by recording vocal parameters for brief periods with the aid of microphones. The first devices produced recorded only a few parameters and for relatively short periods of time, and since microphones were used there was a problem with both privacy and background noise such as the inclusion of voices from nearby people. Recently, microprocessors that can monitor a voice for an entire day have been developed; these use miniaturised accelerometers as vocal sensors. The latest commerciallyavailable version is the Ambulatory Phonation Monitor (APM) (KayPENTAX, Lincoln Park, NJ, USA) which can record several vocal parameters for over 18 hours and supply a series of graphic representations of the variations in these parameters during the recording period. In particular, the APM permits recording vocal load by measuring the cycle dose and distance dose, and evaluates vocal intensity (dB sound pressure level [SPL]), fundamental frequency and total phonation time. This report describes the APM, the use of an accelerometer as a vocal sensor, the importance of its calibration and the parameters it records. In particular, details are given on phonation time, variations in frequency, vocal intensity, phonation density and vocal dose. The role of the APM in voice studies is also described, in addition to its potential clinical applications as demonstrated by the few reports available in the literature. We also discuss our experience with the device in groups of euphonic and dysphonic elementary school teachers.