Reference: Sharh ‘Umdatil-Fiqh – Tape No.4, Question No.39
Question: Sometimes a person hears a sound emanating from the stomach, like the sound of passing wind; so is the wudhoo nullified by that?
Response: No; [have] you heard the hadeeth? Sound emanating from the stomach does not invalidate the wudhoo, so long as you are certain nothing has passed – for certain, and not something you are unsure about.
 The Prophet (sal-Allaahu ‘alayhi wa sallam) was asked about a man who felt something during his prayer – should he stop praying? He said: