"Audio does not sound correct"
I suspect I'm preaching to the converted on this forum, but if you have a complaint about the audio, please include a freewrite report, or come here to explain the problem. When all we get is a tickbox "audio does not sound correct" we don't know if it means:
a tile in one of the sentence-building exercises is silent when you click on it (it just means that no speaker has yet recorded that word individually)
the speaker is saying "test test test" or "De'wI'vam QIp vIQaw'rup" instead of the proper phrase (shouldn't happen, and is a priority to fix)
the audio is missing altogether - i.e. it hasn't been recorded yet, or only one of the M/F voices has been recorded, and Duo tried to play the other one
the speaker coughs or taps the microphone or mumbles while recording
the student can't believe that the sound Q or tlh is real, and thinks the speaker is coughing or mumbling
there is a mispronunciation
the phrase is voiced too slowly or too quickly
there is an audible microphone on/off click at the beginning or end of the recording. (Not ideal, but not a priority, as you can still hear the phrase. Think of it as subspace noise).
A freewrite comment or a post here on what you feel is wrong with the audio will help a lot.
Feel free to comment here on what your audio pet peeves are.
Theoretically, a diphthong should not form there. The y and the w should really only form diphthongs when they follow a vowel in the same syllable. When carefully pronouncing a word like bIyaj'a', proper pronunciation would be to maintain a clear and separate vowel and y.
In reality, when one is speaking normally, and y or w follows a syllable ending in a vowel, the distinction between the preceding vowel and the consonant is often relaxed and a slight diphthong can form.
An interesting additional note is that syllables ending in Ir and Ing also tend to cause the preceding I to close and sound more like the diphthong Iy.
This is not correct.
The Klingon diphthongs are:
aw, ay, ew, ey, Iw, Iy, o, oy, u, uy
Although the word diphthong does not appear in The Klingon Dictionary, he nevertheless describes diphthongs without using the word.
Because w and y are glides, they form diphthongs. You'll notice that I include o and u and not ow or uw: that's because ow and uw would sound exactly the same as o and u, so no Klingon words have ow or uw.
Be careful not to interpret these combinations as diphthongs across syllable boundaries. gho circle has the diphthong o in it. ghoyaj Understand us! does not have the diphthong oy in it, it has gho- plus yaj.
As for Ir or Ing sounding like Iyr or Iyng, you should avoid doing that. TKD says:
I As English i in misfit. Once in a while, it is pronounced like i in zucchini, but this is very rare and it is not yet known exactly what circumstances account for it.
Two of the biggest tells in a Terran accent is saying vee or bee instead of vI- or bI- and stressing a prefix syllable instead of the verb itself. But when the sound following a prefix is y, when does the I end and the y start? I'm listening to myself pretty hard for this. I don't want to artificially extend the IIIII, or stop it by saying bI'yaj. If I'm still voicing the I as I smile for the y sound, I guess that dipthong creeps in.
mayaj, reyaj, boyaj, Duyaj je don't turn the slightest but into ay, ey, oy, uy sounds, but I guess the articulators are closer to ee/Iy when saying I.
Listen to Okrand's descriptions and continue to hold the speakers to account.