How APM collects phonatory data
APM is worn in a waistpack by clients as they go about their normal daily routine. The transducer is a small accelerometer (contact microphone) which is adhered to the base of the client’s neck (just above the sternal notch); it can be hidden by the collar of a shirt or blouse. A cable runs from the accelerometer to the hardware module in the waistpack. The accelerometer senses the vibrations of the skin on the neck that are associated with phonation. In the clinic, the APM system is calibrated by the clinician prior to data collection. The client then leaves the clinic and pursues his daily activities. After wearing APM over a defined period, the unit is returned to the clinic and data is downloaded to a PC for analysis using APM software.
Data analysis includes both graphic and numeric displays of total phonation time, average fundamental frequency (Hz), and amplitude (dB SPL) values. A primary graphic-based display is a “Phonation Profile” that shows phonation times and amplitude levels across a selectable time span ranging from the entire day to various sub-intervals. Not only are values for phonation time and SPL reported, but the graphs also indicate when, during the data collection period, the vocalisations occurred. Additional graphical displays (e.g., histograms) reveal important characteristics of the client’s phonatory behaviour over many hours.It should be noted that APM only collects extracted voice parameters, not actual speech samples. Clients need not be concerned with the confidentiality of their conversations during the day.
How APM works as a vibrotactile feedback device
APM has an additional mode of operation as a feedback device for clients outside the clinic. This is accomplished by means of a vibrotactile unit (about the size of a pager) connected to the APM and worn on the client’s belt or placed in a pocket. The clinician, using APM software, customizes the unit for each client to elicit a vibrotactile sensation when a particular threshold, such as an amplitude value, is exceeded. It is believed that such real-time vibrotactile feedback during routine daily activity will help the client more quickly learn how to modify vocal behavior and achieve desired vocal function, as defined by the clinician.