Issue link: https://digital.copcomm.com/i/713016
C A S Q U A R T E R L Y S U M M E R 2 0 1 6 9 Long before your mind has had a chance to ponder any of this, your auditory system will already have analyzed the sound-pressure wave pattern to extract the following useful pieces of information: "that the fallen objects are indeed made of metal, not wood or plastic; that there is quite a large number of them, certainly more than one or two; that the fallen metal objects do not weigh more than a hundred grams or so each … as well as that their impact occurred in our kitchen, not more than 10 meters away, slightly to the left, and not in the kitchen of our next-door neighbors or in a flat overhead." We are introduced to sinusoidal motion of the mass-spring system which translates to everything which vibrates and, depending on the frequency and amplitude, everything we hear. Then, on to Fourier's description of any function consisting of a mixture of sine waves, and the following Fourier analysis. It's interesting to note that "the workings of the ear only vaguely resemble the calculation of a Fourier spec- trum," but it's still a critical part of understanding and working with sound. There is some impulse analysis and the introduction of using windows of time to estimate the frequency of a sound and calculating the spectrum within the window. One factor is that frequency analysis, in the ear or machines, depends on the length of the sample you get, and how suddenly you open and close the window, if you will. If you want frequency resolu- tion to be high, you need a longer window to do the evaluation, but it will be harder to determine when the sound begins, sort of like Heisenberg's uncer- tainty principle for subatomic particles! Your brain has an advantage over windowed spectrograms in that we can do multi-resolution analysis. In a given time window, the higher the frequency, the greater your pitch resolution. The authors go into a discussion of linear proportionality in resonant systems and filters, which basically is about how, when a filter is tuned to the resonant frequency of the input, it creates an output. If you think of your cochlea as a series of linear mechanical filters, you can start to see where this is going. Next time, we'll get into anatomy, and how all this math and resonance and linearity wind up exciting a pair of stunningly elegant and complex electro- mechanical transducers that bring so much of the world to us—telepathically. D������, I��. 25209 Avenue Tibbitts Valencia, CA 91355 Phone (661) 607‐0206 Fax (661) 257‐2236 www.denecke.com Email: info@denecke.com D������, I��. Makers of the original SyncBox ® Introduces the SB‐4! More features and higher stability than before.