It's probably coming from the front,I thought my noise was at back at first, but it proved to be n/s compression("banana") arm.
Very common, there are loads of threads about it,do a seach.
Get a passenger to listen for you,leaning forward towards the footwell,to see if the noise really is from the front.
Because the wear in the ball joint only needs to be very little for a rattle/knock to appear,garages find it hard to find with just a quick look underneath.