Feel of a surface marked by irregularities, protuberances, or ridges. Subjective characteristic employed as an element of a continuum to define the percepts created by amplitude-modulated noises. Deliberate, consistent amplitude variations which can be viewed as loudness modifications are identified as beats. Larger fluctuation rates , above around 15 Hz, are identified as flutter, while those above around 40 Hz are identified as being rough.
ROUGHNESS: "The grade of sandpaper denotes the roughness."