45. The u sounds are clearly parallel to the i sounds. In both cases we have a laxly articulated short sound, and a diphthong in which the tongue rises towards the end.
The short sound in would, book, etc., is open, and the sign for it is [ᴜ]. Do you notice any difference in the length of the vowel sound in the words should and put, pull and cook? Observe others, if you are uncertain in your own case. (You will sometimes find it hard to determine what is your natural, instinctive way of pronouncing a word, when once you have grown accustomed to watching your own speech.)
When this [ᴜ] is unstressed it becomes [ü][58] or [ə], or is dropped altogether. Thus helpful becomes [helpfül, helpfəl], and should becomes [ʃüd, ʃəd, ʃd, ʃt].
The vowel sound in who is not uniform. (See what was said about the corresponding i sound in § 42). It may begin as close [59], in which case the further rising towards the end reduces the passage so much that we have [w]; who in this case is [huːw]. Or the vowel may begin fairly open and rise to the close position; then who is [hUːu]. When the diphthong is followed by a voiceless sound, it is somewhat shortened; hoot is [huwt] or [hᴜut]; compare root with rude. A half-long vowel is now generally heard in room; some speakers make it quite short.
In unstressed syllables the first element is shortened and often becomes [ü]; thus July is [dʒüw´lai].
Before [ə] the diphthong loses its second element; cruel is [kruəl]. When the [ə] represents a written r, the first element often changes to a vowel with lower tongue position. Thus poor is pronounced [pᴜə, poə], and some educated speakers of southern English even say [pɔː], riming with door, floor; but this can hardly be considered standard English. Notice also the various pronunciations of your, sure. Before spoken [r], as in poorest, enduring, the [ə] becomes very faint or disappears.
The so-called "long u" in such words as due, dew, dude consists of three parts. The second and third are the vowel sounds in do, which have just been discussed; the first is [j], which after voiceless sounds tends to become the voiceless [ç] and even [ʃ], as was mentioned in § 34. Thus tune is in ordinary speech [tjuwn], and often [tçuwn]; in careless speech it may even become [tʃuwn].