Last week there was an article about Regular Verbs and Their Spelling.  The main spelling rule is that the past tense of all regular verbs ends with -ed.

However, the -ed ending is pronounced differently in different words…

 worked – sounds like workt   (just one syllable)
 cleaned – sounds like cleand  (just one syllable)
 started – sounds like startid  (2 syllables)

How do you know which sound to use?
Feel your throat while you say a sound.

For some sounds (‘voiced’ sounds like n, d, and m) you will feel vibration ().  For other sounds (‘unvoiced’ sounds like t, k, and p) you will not feel vibration.
Now feel your throat while you pronounce a regular verb (like work, clean, start) and notice the last sound of the word (work, clean, start)

1. If the last sound was unvoiced (as in work), pronounce the -ed sound as a t
   worked > /workt/; stopped > /stopt/
2. If the last sound was voiced (as in clean), pronounce the -ed as a d
   cleaned > /cleand/; called > /calld/
3. But – if the last sound was a t or d sound, pronounce the -ed as id (which adds a syllable)
   started > /startid/; loaded > /loadid/