Theory of phonetics

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[x] [a]
[aI] resembles Russian [a] between 2 palatalized consonants. For example, чай, пять.

[OI] During pronunciation of [O] the bulk of the tongue is in the back part of the mouth, the back of the tongue is slightly raised. The lips are slightly rounded. It is back low-narrow slightly rounded. While pronouncing [I] the tongue moves forward and upward, towards [I]. The opening between the jaws is wide for [a] and much narrower for [I].

Don’t replace [OI] by Russian [o]. [I] resembles a weak [e].

Diphthongs with [V]-glide

Diphthongs	Warning
[aV] The nucleus is pronounced with the bulk of the tongue in the front part of the mouth, but slightly retracted. The front of the tongue is slightly raised. [a] is front retracted low-broad unrounded. While pronouncing the glide the tongue moves higher and backward. The opening between the jaws is wide for the nucleus and much narrower for the glide.	Don’t replace [V] by [у] and [H]. Don’t protrude the lips.
[OV] The nucleus is pronounced with the central part of the tongue in the [E:] position. [O] is central mid-narrow unrounded. While pronouncing the glide the back of the tongue rises higher moving in the direction towards [V]. The lips are neutral at the beginning of the diphthong but during the glide they are almost as much rounded as for [V].	Don’t replace [OV] by Russian [oу] or [o]. Start [OV] with [E:]. [OV] resembles the sounds in this position: еще у нас.

Diphthongs with [q]-glide

Diphthongs	Warning
[Iq] During the nucleus the bulk of the tongue is in the front part of the mouth cavity. The front of the tongue is raised to the position of [I]. [I] is front-retracted high-broad unrounded. While pronounc-ing the glide the tongue moves back and down towards [q] (its articulation is fully accomplished). The lips are neutral.	Don’t replace [Iq] by [I] or [i:]. Don’t omit the glide [q]. [Iq] resembles the sounds in this position: Учи английский.