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I Duration of sound in our brain (0.1s)

  1. Jan 13, 2017 #1
    a certain sound remains in our brain for 1/10 of a second. The phenomenon of echo can happen only if the distance is at least 17 meters: we say the letter A, which remains in our brain for 1/10s, and the reflection (echo) of A arrives to our ear after that 0.1s....If the distance is shorter than 17 meters we get reverberation.

    Aside from echo and reverberation, when we speak a whole word, like book, we clearly hear each single letter (b-o-o-k). Why doesn't the 0.1s memory of each letter play a factor? that would make each letter overlap in our brain...
  2. jcsd
  3. Jan 13, 2017 #2
    A brain is not like a digital computer which manipulates data according to a linear set of instructions which execute at 'n' amount of CPU ticks per second.
    It is a system which is good at recognizing patterns, and the more a pattern is re-inforced the faster a brain responds to it.
    Last edited: Jan 13, 2017
  4. Jan 14, 2017 #3


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    This is a very complicated subject. Our hearing does both frequency and time analysis on the sounds we receive. When a sound arrives at our ear via two different paths, There are two possible effects. A long relative delay can be distinguished as two separate sounds (an echo) and a short relative delay will result in a distinguishable change in the frequency spectrum of the sound which you can't resolve as a time difference. There is a good analogy with reception of analogue TV signals under 'multipath conditions'. Reflected signals from a distant building will produce identifiable low level delayed images, superimposed on the main picture which we actually call echos. (Football players running across a green field will each have faint a shadow, following them). Reflections from a nearby obstruction (short relative delay) are invisible (not resolved) but can cause the sound or colour information to be distorted because they sit in a part of the TV signal spectrum that's different from the coarse detail (main shapes in the picture).
    Your brain evolved to get the most information out of the sounds it receives for the 'cost' of running your hearing system. Your 'memory' of a situation is formed by a complicated signal processing system (different from the DSP that we can do with computers- see rootone's comments). Was your '1/10s' figure just a rough idea?
    Your example of the way the word 'book' is recognised is a bit too simplistic because that word is very familiar and you associate that sound pattern with all your other memories of books. The response to it is very different from hearing the (made up) word 'foons'. People say that 'we hear what we want to hear', and I agree. The total input of information into our brains is far too high to deal with so we have to condense it into understandable and familiar concepts. That process starts very early on in our processing systems. (The same thing happens with vision, with a lot of processing taking part on the actual surface of the retina.) No one 'designed' these systems.
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