Chapter 1 Summery Notes - Posted on 2017-06-17 by April Stephenson

1. Sound is made possible through the vibrations of an object displacing the air molecules around it. (Water Ripple Effect)
2. Compression: the displacing of air molecules around the source of noise, pushing them forward into the other air molecules.
3. Rarefaction: When the original air molecules tranfer their energy and then re-adjust leaving space behind their original position
4. Atmospheric pressure: The natural air pressure around us at all times
5. Waveform: the graphic representation of the amplitude of a sound pressure wave over a period of time.
   1. ?Graphic representation of a sound wave almost always uses the vertical axis to represent amplitude, and the horizontal axis to represent time.
6. Amplitude :the measure of increasing or decreasing pressure, or amount of displacement from the normal amount of air pressure
   1. ??? related to what you could call loudness or volume level. 
7. Decibels: the unit of measurement for amplitude.
   1. ?The optimal mixing level for engineers is 85-95 dB SPL
8. ?Frequency: the number of occurrences of a repeating event per unit of time.
9. ?Hertz (Hz): The measurment for Frequency
   1. ?One cycle per second is equal to one Hz. 
   2. Human beings have a frequency range of 20Hz to 20,000Hz or 20kHz 
10. ?Fundamental Frequency: is the most present frequency heard when an instrument plays a note.
11. Phase: a waveforms position in time.
12. Phase Shift: what happens when one waveform is delayed from another and then mixed together. ?
    1. When reverse to 180 degrees and played at the same time, two wave forms will cancel each other out.
13. ?Simple waveforms: waveforms that have some type of uniform shape that is repeated.
    1. ?There are 4 types of simple wave forms:
       1. ??Sine
       2. Triangle
       3. Square
       4. Saw
14. ??Complex waveforms: waveforsm that don’t adhere to a uniform pattern most of the time because the variables going into creating those waveforms are constantly changing.
15. Envelope of a waveform: variations in amplitude that occur in a period of time over the duration of a note (ADSR):
    1. ?Attack
    2. Decay
    3. Sustain
    4. Release?

??Ear Development:

1. Pinna (Outer Ear): The outer ear helps localize sound and filters out certain frequencies because of its shape. 
   1. the shape of our outer ear is especially designed to produce phase cancelations in certain circumstances.
   2. phase cancelations and the amplitude of a sound can tell us where a sound source is located
2. Tympanic Membrane (eardrum): The ear drum is a small flap of skin that vibrates back and forth along with the sound wave vibrations.?
3. Malleus (Hammer), Incus (Anvil), Stapes (Stirrup)
   1. :The malleus is connected to the tympanic membrane and rotates back and forth with the vibrations the ear canal is receiving. 
   2.  the malleus causes the incus to push on the stapes which is connected to the cochlea.
4. Golden Ration: 2k-7k Hz | 85-90 db 

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