What sound is made by the suffix ed in missed spelled added?

The sound made by the suffix "-ed" in "missed", "spelled", and "added" is /t/ (as in "cat").

Here's why:

* Missed: The "-ed" makes a /t/ sound, as in "mit".

* Spelled: The "-ed" makes a /t/ sound, as in "spelt".

* Added: The "-ed" makes a /t/ sound, as in "add-it".

This is because the "-ed" suffix is pronounced as /t/ when the preceding sound is a voiceless consonant (like /s/, /p/, /k/, /t/, /f/, /th/).