The term 'Sound of Disbelief' is often used to describe the various sounds people make when they are surprised or shocked. The crossword solutions for this term are 'HUMPH' (5 letters), 'GASP' (4 letters), 'Heh' (3 letters) and 'Hah' (3 letters). HUMPH is a sound made to express disapproval, while GASP is a sharp intake of breath usually made in surprise. Heh and Hah are both sounds of laughter, but Heh is usually used to express mild amusement while Hah is used to express disbelief or surprise.