Random, unexplained auto playback on your computer can interrupt a video you're trying to watch or break your concentration while you're working. Sometimes an advertisement or media file will fire-up in a background program and leave you clueless as to where the sound is coming from. When people use computers, they typically run more than one program at a time and have a multitude of open Web browser windows left unattended, which creates a lot of possible sources for your troublesome music.
Check Web Browser
While it's not considered a best practice in the industry, some websites feature advertisements, videos and other audio content that automatically starts as soon as the page finishes loading. Try checking your Web browser windows and tabs for unsolicited media playback. You can stop the sound by closing the source tab. Some browsers, like Google Chrome, will display a speaker icon on any tabs with audio playback. According to the tech news site TheNextWeb, Google has not built-in tab muting for tabs because they do not believe they should police content. However, you can install program extensions like Mute Everything and MuteTab for Google Chrome and Muter Firefox to add tab-muting capabilities (links in Resources). The browser extensions add mute buttons to browser windows that toggle sound.
Rule Out Running Programs
Check your other running programs, if none of your open browser windows are responsible for the sound. You can bring up a list of all running programs in the Task Manager by pressing "Ctrl-Shift-Esc" and selecting the "Processes" tab. If the program doesn't feature a mute or pause option, you can stop the sound by closing it. Media editing and playback programs, like Windows Movie Maker and iTunes, are likely culprits, because of the constant sound sources they work with. Video games tend to have background music and frequent sound effects. Most other programs only use sound for event notifications and won't produce continuous sound. Additionally, a program that has crashed or encountered an error while playing back audio content can get stuck, leaving you with no way to close the program.
Disable Startup Programs
If the sound starts as soon as your computer logs in to Windows, or after rebooting the system, check your Startup programs list for programs that could produce background sound. You can view the Startup tab by pressing "Ctrl-Shift-Esc" and selecting the "Startup" tab. You can stop individual programs from launching on boot by selecting on the program on the list and clicking on "Disable."
Picking up Radio
If your computer speakers are playing back sound that can't be tied to a program, it's possible that your computer is picking up a radio signal. Poorly shielded speaker wiring can act like an antenna and playback audio through it, if it picks up a signal. The longer the wire, the more likely it will pick up radio signals. You may be able to stop the radio interference by moving the wiring, replacing the wiring or wrapping the wiring in a coil.