Accent and Pronunciation - the sound of "ed"

The past form of regular verbs ends with "ed". Pronouncing "ed" incorrectly is something that contributes to an “accent”. However, with some understanding and practice, this is something anyone can correct.

If the last sound of a regular verb is "p, f, k, sh, ch, s, or "θ th unvoiced", then "ed" sounds like "t". These sounds, "p, f, k, sh, ch, s and "θ th unvoiced"", are called unvoiced sounds. They are called unvoiced because there is no vibration of the vocal cords when we make them. We pronounce "ed" as a "t" sound when the last sound of a regular verb is unvoiced, or not voiced. For example, in the words "stopped", "watched", "walked", "faxed", "priced", "finished", "worked", "produced", and "washed", "ed" sounds like "t".

The remaining sounds in English are voiced. These sounds are called voiced because there is a vibration of the vocal cords when we make them. If a verb ends with a voiced sound, then "ed" sounds like "d". For example, in the words "stayed", "emailed", "compared", "cared", "pleased", "discovered", "played", and "considered", "ed" sounds like "d".

If the last sound of a verb is "t" or "d", then "ed" is pronounced like this "əd". For example, "ed" has this sound in the words "quoted", "decided", "ended", "contrasted", "needed", and "wanted".

voiced - Longman Dictionary of Contemporary English

unvoiced - Longman Dictionary of Contemporary English