Why can I hear warbling when listening to a DAB tuner?

DAB in the UK is transmitted in MPEG2 format using a perceptual coder system which removes information on the basis of 'least audible first' and most of the time it regards information above 17kHz as inaudible. The warbling sound many people complain of when listening to DAB is when the MPEG2 system (which is a compression format) decides on a moment-by-moment basis on how much audio bandwidth to allow through and the higher frequency information varies quite quickly resulting in a 'warbling'