Rumble noise over bumps

[Midg]

Hello, I have a clio mk2 1999 Alizé. Just recently I have been hearing a rumbling noise from the front. For example, if I was to drive down a dirt track with loads of bumps and holes (not deep), not driving fast, maybe 15-20 mph, the front end rumbles. We have had someone to look but can't say what it is. Hopefully someone on here can help with ideas.

Thanks