Schwa sound is a short and lax vowel. It substitutes for all vowels when they occur in unstressed syllables. To produce the sound, the lips are slightly parted and there is no tension at all. The tounge lies relaxedon the floor of the mouth; it's sides and tip do not touch and part of the mouth., e.g. utensil (wherein stress is in second syllable)

(hoping I help you for this idea of mine)