There is only one file type that uses the .VAP extension:
Dialogic Indexed Voice Audio File
Voice recording file created in Dialogic's VAP file format; contains an indexed, or annotated, collection of .VOX or .WAV files, which use ADPCM (Adaptive Differential Pulse Code Modulation) encoding and specific sampling frequencies.
VAP files are used for storing multiple voice recordings in a single file and navigating them in software or hardware.
Updated: November 10, 2017