the best solution for that is do the following.
- In Pidgin, select Preferences from the Tools menu (or simply press Ctrl+P)
- Click on the Sounds tab
- In the Method drop down list, select Command
- In the Sound command text box, enter the following: aplay %s
- Select an event with an assigned sound from the Sound Events list
- Click the Test button. You should now hear the notification sound
- Click the Close button.