Figure 1. Schematic diagram illustrating the major steps involved in data acquisition of 7 smartphone tasks assessing voice, balance, gait, finger tapping, reaction time, rest tremor, and postural tremor.
For the voice task, using the inbuilt microphone, we recorded the sustained phonation “aaah”; the participants were instructed to “Hold the phone to your ear, take a deep breath, and say “aaah” at a comfortable and steady, tone and level, for as long as you can.” For the balance task, using the smartphone inertial measurement units (IMUs), we collected triaxial accelerometer sensor data; the participants were instructed to “Stand up straight and place the phone in your pocket. When the buzzer vibrates, stay standing until the buzzer vibrates again.” For the gait task, using the smartphone IMUs, we collected triaxial accelerometer sensor data; the participants were instructed to “Stand up and place the phone in your pocket. When the buzzer vibrates, walk forward 20 yards. Then, stop, turn around, and walk back again.” For the finger tapping task, using the touch screen sensors and timer, we recorded time and location (x-y screen coordinate position) of finger touch; the participants were instructed to “Tap the buttons below with the index and middle fingers of 1 hand alternatively, in a regular rhythm.” For the reaction time task, using the touch screen sensors and timer, we recorded the time of stimulus onset (appearance/disappearance of a screen button) and response (press/release the screen button) along with location (x-y screen coordinate position) of finger touch; the participants were instructed to “Press the screen button below as soon as it appears; release as soon as it disappears.” For the rest tremor task, using the smartphone IMUs, we collected triaxial accelerometer sensor data; the participants were instructed to “Sit upright, hold the phone in your tremor dominant hand and rest it lightly in your lap, and close your eyes and count backward from 100.” For the postural tremor task, using the smartphone IMUs, we collected triaxial accelerometer sensor data; the participants were instructed to “Sit upright and hold the phone in your tremor dominant hand, with the arm outstretched in front of you.”