phonetics- assimilation of voice

ASSIMILATION
ESTABLISHED PROGRESSIVE ASSIMILATION OF VOICE

Due to economy of effort all sounds are affected by their environment to some extent. This economy of effort may occur at the vocal bands or result from the accomodation between two articulations.
Most nouns add an orthographic s to make their plural form: book- books, dog-dogs. However, the pronunciation of the plural morpheme varies according to the noun to which it is added.
The general rule is that the plural morpheme must agree in voicing with the last sound of the noun. book / buk/ books / buks/ dog /dQg / dogs /dQgz/
Assimilation is a phonological process due to economy of effort by which sounds are influenced by neighbouring sounds and come to share some or all of their phonetic characteristics.
In this case the process is also established, which means it is obligatory.
It is progressive because one sound carries its influence forward to the sound that follows.
It is assimilation of voice or voice assimilation because the economy of effort is at the vocal cords
1. Established progresive assimilation of voice
When does this process take place?
1. In the realisation of the plural morpheme cups / kVps/ dogs /dQgz/ brushes /brVSIz/ /brVS@z/ necks /neks/ tables/teIblz/ roses /"r@uzIz/ /"r@uz@z/ rats /r{ts/ cows/kauz/ churches /"tS3:tSIz/ "tS3:tS@z/
The plural morpheme is realised as a voiceless /s/when the noun ends in............................
The plural morpheme is realised as a voiced /z/ when the noun ends in…………………………………
The plural morpheme is realised as an extra syllable / Iz/or / @z/ when…………………….
Remember that NOT ALL PLURAL MORPHEMES ARE REALISED BY THIS PROCESS OF ASSIMILATION
2. In the realisation of the third person singular morpheme
He