Letoa phonemes are drawn from natural languages across the planet Toa. A number of sounds are not used in Letoa which would be used in an auxiliary language here on Earth. Others are included which we might omit, but cultural factors play a role in designing auxiliary languages on both Toa and Earth.
Letoa has twenty phonemes. Five are vowels and fifteen are consonants. They are arranged in simple syllables. Their canonical sounds are given below along with some common variations licensed by the Letoa Academy. Variations are not normally reflected in writing.
Letoa is transcribed here in the Roman alphabet.
Vowels
Letoa uses the five classic vowel positions familiar on Earth. There is an oral vowel at each position.
| Front | Central | Back | |
| Close | i | u | |
| Middle | e | o | |
| Open | a |
Vowels should keep the same sound in all positions. All vowels are pronounced in full. So words like kai or kua have two syllables, not one. Diphthongs are sometimes heard in rapid speech but the practice is discouraged.
Where two identical vowels meet in compounding, one is deleted.
Three variations in vowel quality are licensed, though dispreferred:
In many areas, middle vowels are mid-close or mid-open for some or all of the time. So /e̞ , o̞/ become /e, o/ or /ɛ, ɔ/.
A few areas raise unstressed a to /ɐ/.
/i, u/ may reduce to /j, w / between two other vowels. This can still happen at word boundaries unless a pause intervenes. The Letoa Academy is currently considering a proposal to make this practice canonical.
Consonants
Letoa stops may be voiced or voiceless. There are also voiced sonorants, plus voiceless fricatives and affricates. The canonical sounds of Letoa consonants are as follows:
| Lab. | Alv. | Pal. | Vel. | Glot. | |
| Nas. | m | n | |||
| Stop | b, p | d, t | g, k | ||
| Affric. | z | c | |||
| Fric. | s | x | h | ||
| Trill | r | ||||
| Lat. | l |
Most of these phonemes have their IPA values at all times. The following points should be noted:
Voiced stops are fully voiced as in French. The onset of voicing is slightly delayed in English.
Z represents IPA /t͡s/. So it is pronounced as in pizza.
C and x are fully palatal. They are similar to their English counterparts but are made further back in the mouth, so approximately: /t͡ʃ/, /ʃ/. C is pronounced as in cello. X has the value it sometimes has in Portuguese, e.g. roxo (raven).
The Letoa Academy licenses the following variations:
An unwritten glottal stop /ʔ/ may be sounded between words where two identical vowels meet. Younger speakers though, tend to delete the first vowel instead, much to the annoyance of their seniors.
Speakers of languages that lack one of the stop series may replace it with ejectives, aspirates or doubled plain stops.
Any other lateral may replace l and any other rhotic may replace r.
H may be replaced by /x/, /ʔ/, or /ɸ/.
Suprasegmental Features
The language is syllable-timed.
Syllables must be (C)V(N) in shape(where V=any vowel, C=any consonant and N=any nasal). The stress in Letoa always falls on the penultimate vowel.
Overall, Letoa phonemes present few difficulties to speakers of most Rotoa languages. This helps ensure that Letoa is well-suited to its role as the global auxiliary language.