Loud Hum Sound in Audio Applications

amy

I get a loud beep or hum sound whenever I hit the pause button on a number of applications, including XMMX, Rhythmbox Music Player, Sound Juicer and even Movie Player.

In most cases, the beep lasts for about 2 seconds, but with XMMX, it continues until I hit the stop button.

I get the same sound with speakers or headphones, even when the headphones are connected to the sound card and the speakers are switched off.

I don't have the problem with Amarok.

I have my Dell Inspiron 9300 laptop connected to an external sound card - Tascam US-122. This probably has something to do with the problem as the sound does not happen with the Dell's internal card.

I would welcome any advice.

Jay