Q: Thumping sounds while driving over sharp bumps

I have a high-mileage car with approximately 150,000 miles on it. It has an automatic transmission. It's been making some noises in the front end of the car on the left side. These thumping sounds occur when I hit a sharp bump during driving. Bumps are not the issue, but only sharp ones would cause the noise. At the shop, they had the struts replaced as they thought that was making the noise. It didn't help however. The noise can be heard only from the inside of the car. I went to the dealer and had the strut bushings and top links replaced, as they were bad. I had the alignment checked as well. It was fine. I checked every part I could, including bolts and lower ball joits as well as the exhaust. There are no loose parts either. The car steering is fine. The sound is still noticeable. Besides sharp bumps, the sound is also heard if I drive slowly over a sharp speed bump, making the noise at the end of the speed bump. It sounds like something heavy. Do you have any idea what could be making this thumping noise? Thanks.