Diesel clatter is definitely music to the ears. However, a true diesel ear must be tuned to subtlties. There is such a thing as 'nailing' which is a harder sound and is sometimes caused by dirty injectors. You should periodically run diesel purge thru the fuel system. My 85td definitely sounds different when it is running on pure purge and does sound different afterwards when things are cleaner.
The diesel forum will provide good info on how to run the purge through your engine. And, if you're really desperate, there is a thread in which someone put their laptop on top of their engine and recorded the sound.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13