Experimental design and voxel decomposition method. A: fifty examples from the original set of 165 natural sounds used in Ref. 7 and in the current study, ordered by how often participants reported hearing them in daily life. An additional 27 music stimuli were added to this set of 165 for the current experiment. B: scanning paradigm and task structure. Each 2-s sound stimulus was repeated three times consecutively, with one repetition (the second or third) being 12 dB quieter. Subjects were instructed to press a button when they detected this quieter sound. A sparse scanning sequence was used, in which one fMRI volume was acquired in the silent period between stimuli. C: diagram depicting the voxel decomposition method, reproduced from Ref. 7. The average response of each voxel to the 192 sounds is represented as a vector, and the response vector for every voxel from all 20 subjects is concatenated into a matrix (192 sounds × 26,792 voxels). This matrix is then factorized into a response profile matrix (192 sounds × N components) and a voxel weight matrix (N components × 26,792 voxels).