Hola mi gente ! I've been struggling with this for quite a long time and I thought I'd share with you this , some people may be interested in so without further ado words with ending voiced consonants are weak as a result they sound unvoiced let's take for example the word Flowers /ˈflaʊ.ɚrz/ the ending voiced consonant is the Z sound but Z at the end of the word fades almost immediately into an unvoiced s , a weak light S and not a very strong S. it doesn't sound like that FLOWERSSS or like this FLOWERZZZ
another example the word garage /gəˈrɑːʒ/ it doesn't sound like garaʒʒʒ or garaʃʃʃ but garaʃ , a weak light ʃ and not a very strong ʃ
Pronounciation of the word FLOWERS : http://vocaroo.com/i/s0kQDpAxXAiQ
Pronounciation of the word GARAGE : http://vocaroo.com/i/s1QHOMP4BHpw
Nice observation.
As far as I can tell, this issue is common to all accents. My non-expert take on the issue is that the sound is at the end of the word and so the mouth then has to release. The voice may stop slightly sooner than the pushing of the air through the mouth.
If you continued to another vowel sound (e.g. "flowers and.."), the /z/ sound would be cleaner and not tail off into an /s/
