The voiced sound [v] is usually written v.
Sounds very like [f, v] can be produced with both lips. Though they do not ordinarily occur in English, it will be good practice for you to produce them.
When [v] is final, it is not voiced to the end, but passes into whispered [v] (symbol v̥), which sounds very much like voiceless [f]; in other words, the vocal chords cease to vibrate before the breath ceases to pass between the lower lip and the upper teeth. We may say: final [v] is devocalised.
Observe thief, but thieves and to thieve; loaf, but loaves; shelf, but shelves and to shelve.
The ph in nephew is pronounced [v], but [f] is heard in dialects.
28. Point continuants.—We have seen above (§ 24) that in English the tongue, as a matter of fact, rarely touches the teeth in the case of point stops. Similarly the narrowing of the passage which leads to the production of point continuants (except [θ,ð]) is not necessarily between the tongue and the teeth; in some cases it is indeed a good deal farther back.
The point continuants include:
1. The hushing, hissing,[30] and lisping sounds, and the r sounds, in which the place of articulation is along the middle line of the mouth (medial formation); and
2. The l sounds, the narrowing for which is between the side rim or rims of the tongue and the side teeth (lateral formation).