'Abbad bin Tamim narrated that his paternal uncle said:
"A complaint was made to the Prophet about a man who sensed something (some doubt about his ablution) during prayer. He said: 'No (he does not have to perform ablution) unless he notices a smell or hears a sound.'" (IT)
English reference (IT): Vol. 1, Book 1, Hadith 513 (IT)
Arabic reference (IT): Book 1, Hadith 553 (IT)