Possible Clues:

• Sound of soldier in pub
• Like the left brain, in pop psychology
• Sound from American serving in bar
• Reasonable person who serves in pub
• Sound made by entry: one short ring
• Sensible soldier visiting pub
• Man who's served in pub with good reason
• Serving US soldier in one's pub is only to be expected
• I go and call afresh, being reasonable
• Serving American in pub is making sense