Three Kinds of pronunciation

/t/ /d/ / ɪd/

/t/

1) verbs ending in -ed preceded by a voiceless consonant /p, k, f, ʃ, ʧ, s, θ/ -> pronounce /t/.

Example: I stop - I stopped /stɒpt/

/d/

2) verbs ending in -ed preceded by a voiced consonant /b, g, v, ʒ, ʤ, z, ð, l, m, n/ or a vowel -> pronounce /d/

Example: I clean - I cleaned /kli:nd/

/ɪd/

3) verbs ending in -ed preceded by /t/ or /d/-> pronounce /ɪd/

Example: I visit - I visited /vɪzɪtɪd/

Work Site http://www.englisch-hilfen.de/en/grammar/s

imple_past_pronunciation_ed.htm