I just met a guy whose thing is acoustic engineering. Builds speakers, amps, etc, consults on room layouts, and a bunch of stuff, based in Pretoria. I got a test CD from him that has a wide range of individual frequencies, white brown and pink noise, etc. I recall someone was looking for a test CD a while back. If anyone is interested, his name is Eben, number 0823265044.
(It was fascinating moving around my room, changing speaker toe and separation, and finding loud spots/dead spots/bad image spots!)
Also interesting to hear 40Hz as sound, but 31.5Hz just as the driver thudding. For the record, I can't pick up the 16KHz signal with both ears, and even the 12.5KHz sounds extremely high-pitched, far higher than the base frequency of any instrument except maybe King Crimson in a weird moment.
(It was fascinating moving around my room, changing speaker toe and separation, and finding loud spots/dead spots/bad image spots!)
Also interesting to hear 40Hz as sound, but 31.5Hz just as the driver thudding. For the record, I can't pick up the 16KHz signal with both ears, and even the 12.5KHz sounds extremely high-pitched, far higher than the base frequency of any instrument except maybe King Crimson in a weird moment.