Even if one disagrees with what I have said about the application of the IPA to English, these remarks should be accepted as unquestionably true as regards Nuu, since the pronunciation of Nuu, rather than English, is the real subject of this article.
Nuu's Vowels (Handwritten Version)
Nuu's original alphabet was designed before the rise of Internet, and no regard was paid to high-speed online transfer. Further below, a Romanization is provided.
Nuu has 288 vowels. There are 24 basic vowels, 12 unrounded and 12 rounded, none nasalized and all toneless. Each of these 24 has a nasalized toneless counterpart. Moreover each of the 48 unnasalized and nasalized toneless vowels has five tone-bearing counterparts,
Below, I have presented the International Phonetic Alphabet's famous vowel trapezoid as well as Nuu's vowel trapezoid, derived largely from it.
Nuu has no central or centralized vowels. So three vowels in the second row of the IPA trapezoid have been moved in Nuu to align with front and back vowels. This does not constitute a disagreement with the IPA's selection of the point of articulation of these vowels, as much as a matter of symmetry. Actually, the implied difference in pronunciation is so slight that it doesn't matter.
Three vowels have been added in the fifth row, and various minor changes have been made elsewhere, all reflecting the comments made above.
Here the words round and unround have been substituted for rounded and unrounded. An unnasalized vowel, like any of the vowels of English, Spanish or Russian, is called an oral vowel. Nasalized vowels, like some of those in French, Polish and Hindi, are called nasal vowels. Nuu has five tones, four as in Chinese, level, rising, falling-rising and falling. The fifth tone is rising-falling. A vowel in any of these tones is called a tonic vowel. A vowel carrying no tone is called an atonic vowel. In Figure 2, the vowels in the leftmost diagonal line and in the vertical line second from the right are unround vowels. The vowel with which each unround vowel is paired is the round counterpart, pronounced in exactly the same position but with distinct labialization. All the vowels in Nuu's trapezoid are atonic and oral, as indicated.
With the qualifications made above as regards IPA and IPAE, the vowels in the leftmost diagonal line in Figure 2, proceeding from top to bottom, are pronounced as in the following General American English words:
BEAT, BIT, BAIT, BET, BAT, BOT
The upper 5 vowels in the vertical line second from the right are pronounced as in these words:
BOOT, PUT, BOAT, BUTT, BOUGHT
The sixth vowel is a low back vowel whose pronunciation is to be inferred from comments above.
Figure 3 shows the diacritic marks that are used to denote vowel nasality and tone.
1...Tilde (Nasality)
2...Macron (Level tone)
3...Acute (Rising tone)
4...Caron (Falling-rising tone)
5...Grave (Falling tone)
6...Circumflex (Rising-falling tone)

Figure 3: Nuu's Diacritic Marks for Vowels
Each of the 24 atonic oral vowels has an atonic nasal counterpart, which is shown by placing a tilde over the vowel. Atonic vowels, both oral and nasal, therefore are 48 in number. For each of these 48 atonic vowels, there are 5 tonic counterparts, and these tonic vowels are denoted by placing appropriate diacritic marks numbers 2 through 6 in Figure 3, over the letters denoting atonic vowels. If a vowel is both nasal and tonic, the tone-diacritic is written over the tilde. By this procedure, Nuu's entire vowel schema, shown in Figure 4, is produced.
Figure 4: Nuu's Complete Vowel Schema
(Handwritten Version)
Figure 5 is a specimen of handwritten Nuu and contains many of the vowels tabulated in Figure 4.

Figure 5: A Specimen of Handwritten Nuu
Nuu's Vowels (Romanized Version)
Figure 6 shows the Romanizations of the handwritten vowels of Nuu, each in the same relative position in the table as in the diagram in Figure 2.

Figure 6: Nuu's Atonic Oral Vowels
(Round and Unround) (Romanized Version)
Instead of superposed diacritic marks, postposed numerals and punctuation marks are used with the Romanizations of Nuu's vowels.
If an atonic vowels does not have an apostrophe ('), nasality is indicated by suffixing a semicolon (;). If it bears an apostrophe, the apostrophe is changed to a quotation mark (") to indicate nasality. This can be seen in the first two columns in Figure 8. Tonic vowels, oral and nasal, are rendered by adding numerals 1,2,3,4,5,6,7,8,9 or 0 to the vowels in the first column of Figure 8, in accordance with the following table.

Figure 7: Romanized Nuu's Vowel Suffixes
By application of the numerals and punctuation marks used as diacritics, the whole schema of Nuu's vowels as displayed in Figure 4, may be Romanized. The Romanizations are tabulated in below in Figure 8. Note however that, because of limitations in space, Figure 8 is transposed matrixwise with respect to Figure 4, that is, rows 1 through 12 have become columns 1 through 12, and columns 1 through 24 have become rows 1 through 24.
Figure 8: Nuu's Complete Vowel Schema
(Romanized Version)
Figure 9 is a specimen of Romanized Nuu and contains many of the vowels tabulated in Figure 8. Figures 5 and 9 contain entirely unrelated passages.
Figure 9: A Specimen of Romanized Nuu