Letoa phonemes are drawn from natural languages across the planet Toa. All are common there. Some would not appear in an auxiliary language here on Earth but cultural factors play a role in designing auxiliary languages on both Toa and Earth.
Letoa has twenty-five phonemes. Ten 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 plus a nasal vowel.
| Front | Central | Back | |
| Close | i, ĩ | u,ũ | |
| Middle | e, ẽ | o, õ | |
| Open | a, ã |
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.
Adjacent vowels should share the same orality. If one of the pair is nasal the other should be nasal too.
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 , ẽ̞, õ̞ / become /e, o, ẽ, õ/ or /ɛ, ɔ, ɛ̃, ɔ̃/.
A few areas raise unstressed a, ã to /ɐ, ɐ̃/.
/i, u, ĩ, ũ/ often reduce to /j, w, ɲ, w̃ / between vowels including at word boundaries unless a pause intervenes. The Letoa Academy is currently considering a proposal to make this practice canonical.
Consonants
Letoa stops and affricates may be voiced or voiceless. In addition, there are sonorants, fricatives and affricates. The canonical sounds of Letoa consonants are shown in the table below.
| Lab. | Alv. | Pal. | Vel. | Glott. | |
| Nas. | m | n | |||
| Stop | b, p | d, t | g, k | ||
| Affric. | ts | ch | |||
| Fric. | s | sh | 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.
Ch and sh are fully palatal. They are similar to English ch and sh but are made further back in the mouth.
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.
The unwritten glottal stop is also used where oral and nasal vowels meet across word boundaries.
Speakers of languages that lack voiced stops may replace them with ejectives.
Some speakers replace the plain series with aspirates.
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 in shape (where V=any vowel and C=any consonant). The stress in Letoa always falls on the penultimate vowel.
Overall, Letoa phonemes present few difficulties to speakers of Rotoa languages. This helps ensure that Letoa is well-suited to its role as the global auxiliary language.