I agree with mcparadise.
Your tie rods might make noise, but this noise would not be emanating from underneath the driver’s seat. This could be something as simple as a disconnected exhaust system hanger. Or it could be something more serious, like a motor or transmission mount.
Since your mechanic seems to have no clue, why not ask for the refund that he offered, and then take it to a different mechanic? Just be sure that you DON’T take the car to Midas, Meineke, Monro, Sears, or any other chain operation.