Subject: Band noise From: Yoshitaka Nakajima <nakajima(at)KYUSHU-ID.AC.JP> Date: Fri, 6 Jun 1997 15:38:47 +0900Dear Dr. Husain, I often employ a very primitive technique to generate noise, which might be criticized in the field of acoustic engineering. For people in the field of auditory psychology, however, the technique seems practical (People who are not studying practical things are sometimes practical.). 1. Divide the frequency band into N cells (= subbands). The cells are numbered from 1 to N according to their center frequencies. The cells must be small enough compared with critical bands (or auditory filters). 2. Choose a representative component, whose frequency and initial phase are determined randomly, from the cells 1 and 2. Choose a representative in the same way from the cells 2 and 3 (Notice that the cell 2 has two chances to offer a representative component.). --- Choose a representative from the cells N-1 and N. Choose a representative from the cells N and 1. Thus each cell had two chances to offer a representative, but each time there was a probabilistic competition between two neighboring or farthest cells. All the representative components have the same level. I use HP-BASIC to generate sound, and the above procedure is written as a simple FOR...NEXT loop with two random numbers. The probabilistic competition between cells seems necessary to avoid a perceptual impression of beats, which could be an interesting topic itself. This technique is convenient to control spectral patterns intuitively without difficult mathematics. The perceptual quality of the generated noises was really noise-like. One of my students dared to employ this technique even to synthesize simple Japanese speech. Of course I admit that we sometimes need more rigorous techniques. Best regards, Yoshitaka nakajima(at)kyushu-id.ac.jp