If the 'old mini' sound is a bit like a barking dog in the hold then its the hydraulic power transfer unit, which transfers hydraulic pressure between the green and yellow hydraulic systems in the event of failure of one of the engine driven pumps. The noise is usually heard during engine start when the PTU performs a self test sequence.
Don't know the answer to part b, perhaps we're riding over the taxiway lights? I've done lots of sectors on the Airbus and haven't had the gear fall off yet, but there's a first time for everything.
