There is a wide variation in how patients hear (or don't hear) their mechanical valves. Body position and environment (bathrooms with tile walls vs. carpeted rooms with drapes, etc.) can create widely different levels from non-detectable to a 'soft thump'. Some (rare) people experience levels that are irritating or disturbing all of the time.
Body Acoustics play a major role. IF your heart has been pumping against a stenotic aortic valve for some time, it may have become enlarged as the muscle developed to pump blood through an ever decreasing opening. After surgery, those heart muscles can continue to 'pump hard' until they eventually remodel to the new valve with a lower pressure gradient, assuming your heart has not reached the permanent damage stage. Remodeling can take several months.
I couldn't help but notice your reference to "THE mechanical valve".
Actually there are 4 major Mechanical Valve Manufacturers commonly used in the USA.
These are ATS, Carbomedics, On-X, and St. Jude, ALL designed at least in part by Jack Bokros, Ph.D. who is credited with discovering Pyrolytic Carbon (for an application in the Nuclear Power Industry) which is the material used in the Leaflets of the modern Bi-Leaflet Mechanical Valve Designs. I wrote a post recently outlining the History of the modern BiLeaflet Mechanical Valves under the thread name of MECHANICAL VALVES - History of .........etc.
If you want to learn more about the differences in those valves, read through the Valve Selection Forum and check out the websites of the manufacturers. I confess, as an engineer, I am impressed by the technological advancements offered by the On-X Valves (see
www.heartvalvechoice.com and
www.onxvalves.com) The St. Jude Master's Series Valves have the longest track record for durability, going back to their introduction over 30 years ago.
'AL Capshaw'