I can play .wav files on my Raspberry Pi thru the HDMI montor's speakers using both 'aplay' and 'ffplay'. When I download these sound files then unzip them, they don't play. With 'ffplay', the waveform of the sound file is non-existent. Tried downloading twice, tried unzipping with 2 different utilities, same result. I suspect these files are all empty files. Or am I doing somethng wrong?