There is a definite difference in the engine sound between the IAE V2500 on the CEO and the P&W on the NEO. The P&W is geared which may have something to do with it.
When performing single engine taxi, the right engine is shutdown and the yellow (right) hydraulic system electric pump is then switched on, which wakes up the dog as the pressure drops. When parked, opening the hold doors uses yellow system pressure which may also disturb the dog.