English Phonetic Changes

st, sk, sp

When stressed, st, sk, and sp undergo sound changes;
At the beginning of words, st, sk, and sp change their sound, but at the end of words, they do not change their sound;
Sound changes: skate, skill, square, stand, sport, speak, study
No sound change: interesting, inspiring

Voicing Correspondence

When a voiced consonant follows an unvoiced consonant (S + unvoiced consonants), it only changes to the corresponding voiced consonant when it must be stressed.

Unvoiced consonants: /p/ /t/ /k/
Voiced consonants: /b/ /d/ /ɡ/