Values:
RECORDING_DEVICE_TYPE_UNSPECIFIED (0):
The recording device is unknown.
SMARTPHONE (1):
Speech was recorded on a smartphone.
PC (2):
Speech was recorded using a personal computer
or tablet.
PHONE_LINE (3):
Speech was recorded over a phone line.
VEHICLE (4):
Speech was recorded in a vehicle.
OTHER_OUTDOOR_DEVICE (5):
Speech was recorded outdoors.
OTHER_INDOOR_DEVICE (6):
Speech was recorded indoors.