So, lately I've been really interested in devoicing voiced consonants to their counterparts. I've been studying painstakingly, so I would like to share it with you, and you can tell me if you agree with me or not.
So, I'll start:
1. I have two bookshelves. In this case the word 'have' is pronounced with /v/ sound. However, due to the fact that the next word starts with /t/ sound, it becomes /f/ sound.
'Bookshelves' is pronounced with /v/ sound and ends with /z/ sound, however, due to the fact that it is at the end of a sentence, the /v/ and the /z/ sounds will transform into a very but very ultra week /f/ and /s/ sound.
So the sentence /aɪ hæv tu ˈbʊkˌʃɛlvz/ actually becomes /aɪ hæf tu ˈˈbʊkˌʃɛlfs/ (It's how Google translator pronounces it)
2. Vegetable -> /ˈvɛʤtəbəl/ pronounced with /ʤ/, however, if you try to pronounce 'vegetable' with /ʤ/ sound, it is possible but it's hard, and not only that, but it sounds unnatural.
So, due to the fact that the next sound is /t/ sound, it means that the word 'vegetable' will actually become /vɛʧtəbəl/. The /ʤ/ sound will convert into its voiceless counterpart /ʧ/. Google translate
3. The phrase you've changed a lot. The /ʧ/ sound is actually a mix between the /t/ sound and the /ʧ/ sound. So it means that the preceding sound (/v/) will be devoiced and will become a weak /f/ sound rather than a hard /v/ sound.
Not only that, but it seems like the /ʤ/ sound in 'changed' will become a very weak /ʧ/. So you've changed a lot (/juv ʧeɪnʤd ə lɑt/) becomes /juf ʧeɪnʧt ə lɑt/. Not only that, but it seems like the /d/ in 'changed' will become more of a /t/ sound. Keep in mind, they're becoming very weak counterparts. Here is the audio.
4. He's trying. The same will happen here. He's is normally pronounced with /z/ sound, however, due to the fact that the next word starts with /t/ sound, it will actually become more of a /s/ sound. And it's more common to pronounce the /tr/ cluster as /ʧ/ sound, so /hiz ˈtraɪɪŋ/ will become more like /hisˈtraɪɪŋ/. Audio
5. I moved, same thing happens here. 'Moved' is at the end of a sentence, so it means that the /v/ sound in 'moved' will become a very ultra light /f/ sound.
The /t/ and /ʧ/ sounds seem to devoixe many sounds.
'You move to me', 'I have to go', 'I've been engaged twice' (the /ʤ/ sound will become more of a /ʧ/ sound)
It also happens at the end of words. Never in my wildest dreams -> The /z/ in dreams will actually be a very ultra light /s/ sound, so light that it will sound like a little whispery /s/ sound.
Same happens with 'I have a page' -> the /ʤ/ sound will become very ultra /ʧ/ sound, since it's at the end.
However, if you say 'In my dreams I see you', then the /z/ sound will be strong.
If you say 'I'm gonna change my name', then the /ʤ/ sound in 'change' will be strong.
'I'm gonna move again', in this sentence the /v/ sound will remain and it won't change to /f/ sound.
One last more: It won't change to /f/ sound. In change to, the /ʤ/ sound will actually change to /ʧ/ since the /t/ sound devoices it.
Same with, I have a garage, when it's at the end it seems it becomes a very ultra light /ʧ/ sound instead of the /ʒ/ sound. But if you say 'my garage is big', then /ʒ/ will not change to /ʧ/ and will remain strong.