Devoicing occurs when you drop the last sound in the word. The Speaking English Out Loud Youtube has a good description here: https://www.youtube.com/watch?v=S53LK9vu3D8
Encyclopedia.com provides the definition of devoicing here: https://www.encyclopedia.com/humanities/encyclopedias-almanacs-transcripts-and-maps/devoicing
“In PHONETICS, the process by which SPEECH sounds that are normally voiced are made voiceless immediately after a voiceless obstruent: for example, the /r/ in cream /kriːm/ and the /w/ in twin /twɪn/.
VOICE is slow to build up at the onset of speaking and fades at the end, so that voiced obstruents (stop and fricative consonants) are partly or wholly devoiced in initial and final position, as with the initial and final /d/ in dead /dɛd/ when spoken in isolation.”
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