White noise after playback

Dear all,

Linaro Linux image is used on my SD410C board. I followed the instruction to solder out the stereo jack on J7 analog expansion. I tried to use both aplay and vlc to play a wave file, the symptom is the same. After the playback completes, a few seconds white noise always follows subsequently that output from the headset. Can anybody advise how to solve it? Your help is appreciated!

Thanks & Regards,