Possible Clues:

• Soft vowel sound
• Neutral vowel symbol
• Upside-down 'e'
• Unstressed vowel symbol
• The "u" sound in "census"
• Vowel sound at either end of "America"
• Dictionary's upside-down "e"
• Either side of Alaska?
• It's not a sign of stress
• Sort of sound was weirdly going round church