In May 2019 I wrote about the "-(e)s" suffix in plural nouns, the 3rd person singular form in the Present Simple tense as well as the "-'s" or "-s'" in so-called Saxon Genitive. The rules concerning the pronunciation of the "-ed" suffix of the Past Simple and Past Participle of regular verbs are quite similar: the suffix is voiceless after a voiceless sound, voiced after a voiced one and an additional vowel appears when the consonant is similar to the one in the suffix.
1. After a voiceless consonant "-ed" is pronounced /t/, e.g. walked /wɔːkt/, passed /pɑːst/.
2. After a voiced consonant, semi-vowel, vowel or diphthong "-ed" is pronounced /d/, e.g. bored /bɔːd/, played /pleɪd/.
3. After /t/ or /d/ "-ed" is pronounced /ɪd/ (some sources say it is /əd/), e.g. waited /'weɪtɪd/, faded /'feɪdɪd/.
The error that is the most typical of Polish learners of English is devoicing, namely pronouncing final /d/ as /t/ and /ɪd/ as /ɛt/, /ɛ/ being a Polish vowel represented by the letter "e".
Before a pause /d/ is actually devoiced but not the same as /t/. The details will be explained in a separate post.
Ex.
Put the following verb forms in categories depending on the pronunciation of the "-ed" suffix.
baked, wasted, leaked, amazed, melted, smirked, highlighted, tired, greeted, marked, hated, expired, scoffed, grazed, camped, smiled, raised, jumped, booked, helped, watched, skied, surveyed, regretted, considered, added, missed, fainted
1. /t/ 2. /d/ 3. /ɪd/
KEY
1. /t/ baked, leaked, smirked, marked, scoffed, camped, jumped, booked, helped, watched, missed
2. /d/ amazed, tired, expired, grazed, smiled, raised, skied, surveyed, considered
3. /ɪd/ wasted, melted, highlighted, greeted, hated, regretted, added, fainted