== The Airport card ''might'' be loose ==
'''There is no "sound card"''' only a DSP chip on the motherboard. This would tend to point toward a damaged logic board, or at least that chip.
With proper equipment the fault may be diagnosed but it' not really a DIY kind of repar.
Your call as to spend the money to repair a box that old, or sell laptop for parts and put that money towards a new laptop.
'''If this answer is acceptable please return and mark it.'''
Good Luck,
N.