The suffix ed means past tense. It is always spelled ed, but can be pronounced as either a t or d.
For spelling, listen to hear if a word is past tense (so is spelled ed ) or if it just ends in a d or t sound.
For reading, use the /t/ sound when the letter just before ed is unvoiced (dressed, asked, washed, stuffed). Use the /d/ sound when the sound just before it is voiced and neither t or d. (called, turned, crawled, snowed)
A simple explanation of voiced consonants is that they use the voice. This is easy to test by putting your finger on your throat. If you feel a vibration the consonant is voiced. Here is a list of some voiced consonants. Pronounce each consonant sound and feel the vibration of your vocal chords. b, d, th (as in then), v, l, r, z, j (as in Jane)
What is Voiceless?
Voiceless consonants do not use the voice. They are percussive and use hard sounds. Once again, you can test if a consonant is voiceless by putting your finger on your throat. You will feel no vibration in your throat, just a short explosion of air as you pronounce. Pronounce each of these consonant sounds and feel NO vibration in your throat. p, t, k, s, sh, ch, th (as in thing)