The older and higher mileage your engine is, the noisier it will be on two counts; 1. The most obvious thing is wear and increased clearances in mating parts. Keep those valve clearances to spec. 2. As noise standards have tightened over the years, the OEMs have made effort to quiet mechanical noise by various methods; thicker case covers, noise absorbing material added to parts and panels and engineering strategies such as cam profiles, valve train geometries and noise deadening materials on sliding surfaces such as cam chain tensioners. Change the oil regularly, do the routine maintenance and ignore the little rattles because they'll drive you nuts if you're a worrier.
It may be a pig, but it's a pig with a rocket in it's ass!