pattern - What is a Sound Word™?

_{This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles.}

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If a word conforms to a certain rule, I call it a Sound Word™.

Use the examples below to find the rule.

For those unable to view images, here is a text version of the table:

$$\begin{array}{|c|c|} \hline \text{Sound Words™}&\text{Not Sound Words™}\\ \hline \text{DECAY}&\text{DECOMPOSE}\\ \hline \text{QUEUE}&\text{LINE}\\ \hline \text{EIGHTY}&\text{FOURSCORE}\\ \hline \text{ENEMY}&\text{FOE}\\ \hline \text{EXPEDIENCY}&\text{EFFICIENCY}\\ \hline \text{ESCAPEE}&\text{FUGITIVE}\\ \hline \text{TEDIOUS}&\text{BORING}\\ \hline \text{DEVIOUS}&\text{TRICKY}\\ \hline \text{EXCELLENCY}&\text{EMINENCE}\\ \hline \text{IVY}&\text{VINE}\\ \hline \end{array} $$

Answer

A Sound Word is a word whose every syllable sounds like a letter of the alphabet.

• Decay: DK


• Queue: Q


• Eighty: AT


• Enemy: NME


• Expediency: XPDNC


• Escapee: SKP


• Tedious: TDS



• Devious: DVS


• Excellency: XLNC


• Ivy: IV