Ambulatory Phonation Monitor (APM)


The Ambulatory Phonation Monitor (APM), Model 3200, is a portable device worn by a client in order to extract important parameters of vocal behaviour over an entire day of normal activities.

Developed collaboratively by KayPENTAX, Sensimetrics Corporation, and clinicians at Massachusetts General Hospital, APM is based on years of research and addresses the important issue of how individuals use their voices throughout the day. APM can also help clients with carryover of therapy goals outside the clinical environment via the use of real-time vibrotactile feedback.

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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.

APM is an important addition to the instrumentation tools available to clinicians and researchers interested in voice because it provides objective data on the vocal behavior of clients outside the clinic during normal dailyactivity. This information has previously been provided by clients themselves in qualitative self-reports which were highly subjective and prone to be unreliable. With actual data, clinicians can more effectively manage their patients presenting with vocal disorders.

The information provided by APM may also be of interest to a wide variety of researchers interested in the speech patterns of different clients and occupational groups. In addition to the important objective data the APM provides, the vibrotactile component is a potentially powerful feedback tool to help remind patients, in real time, of abusive vocal behaviors. This feature of APM may enhance therapy carryover and potentially expedite the rehabilitation process of clients with vocal problems