Reducing noise & vibration has long been an aim for the development engineer, and in many cases, levels have been reduced so that many products report very similar results.
It's now becoming clear that it's not just level that counts, but also the quality of the sound from the machine. Is it rough? Does it sound tinny? Does it rattle?
These issues were identified by the automotive industry years ago, and now the sound of a car is as important as the trim level, or even performance. Driving a car is a combination of sensations, of which the sound quality is becoming more important. Are you going to buy a luxury car when the door goes 'clang' when you close it?