You are right. Both, the sound events database and an SPL at known
distances database can be sufficient. However I'm not sure if it is
easy to access to this two databases and adapt each data or making
myself the (calibrated) recordings.
I think that I will need more than 100 sound events.
How did you solved the problem of the ground traffic? Did you had to
measure yourself the typical SPL at known distances?
Surely what you really need is a database of typical SPL levels for certain
sound sources at known distances?
I work for a company producing Level D certifiable sound systems for use in
the highest fidelity sound systems, and reproduction must EXACTLY match the
source aircraft, but once you accept general sounds (as opposed to SPECIFIC
ones) there is no reference SPL only representative levels - I face this
problem when representing the ground traffic around the aircraft while on
the ground (push-back trucks, luggage carts, etc)