Muhammad bin Amr bin Ata' said: I saw Sayyiduna al-Sa'ib bin Khabbab (may Allah be pleased with him) smelling his garment, so I asked him: "May Allah have mercy on you, why is this?" He said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Ablution is only broken by passing wind or hearing a sound."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6592