Chosen Solution

For no reason sound level from headset become very low - can hardly hear. Have to use speaker function to talk. Any ideas?

If you have been using the same headset, and the volume decreased substantially, and the volume settings are all the same, and you have set them to the max, then you have blown a transistor. This is a hardware problem, which requires a hardware solution. Go talk with an Apple Genius - I doubt anyone else can help you.

Try cleaning the contacts. -Me-