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SOUND - Coggle Diagram

- - - - Ultrasonic - above audible
      - Infrasonic - below audible
  - - - pressure amplitude is proportional to displacement amplitude
      - waves of shorter wavelengths have greater pressure variation for a given amplitude
    - - B = - P ( x,t ) / ( dV / V )
    - - dV / V = ∂y ( x,t ) / ∂x
      - p ( x,t ) = - B ∂y ( x,t ) / ∂x
      - p ( x,t ) = BkA sin ( kx -ωt )
      - p max = BkA pressure amplitude
- - - - inertia is related to mass which can be described as density or mass/volume
  - - - the quantity of fluid set in motion in time
    - - B = - pressure change / fractional vol change
      - ∆p / −Avyt/ Avt
    - - ∆pAt
      - B ( vy / v ) At
      - ( pvt A ) vy
      - v = √ ( B / ρ )
  - - - the reasoning is the same as in fluid
      - v = √ ( Y / ρ )
  - - - R : gas constant = 8.514 ( J / mol. K )
      - ɣ = ratio of heat capacities
      - M = molar mass
- - - - the intensity is the time average of
        p(x,t) vy(x,t) , thus
        
        I = 1/2 BωkA^2
        
        ω = vk
        
        v^2 = B / ρ
        
        I = 1/2 √ (ρB) ω^2 A^2
        
        the equation shows why in a stereo system, a low frequency woofer has to vibrate with much larger amplitude than a high frequency tweeter to produce the same sound intensity
      - Intensity and pressure amplitude, I :
        
        I = ωp max ^2 / 2Bk
        
        vp max^2 / 2B
        
        p max^2 / 2ρv
        
        p max^2 / 2 √ (ρB)
  - - - an architect’s job when designing an auditorium is to tailor sound reflections so that the intensity is uniform all around
        
        The decibel scale.
        The sound intensity level β is defined as β = (10 dB) log I / I 0
        it is expressed in decibel, dB
        
        Loudness
        
        psychological response to a sound. It depends on
        both the intensity and the frequency of sound
        
        there is no simple relation between physical measurement
        and psychological measurement.
- - - - when waves add up to make a larger amplitude
    - - when waves cancel each other out
- - - - as vs → v , λ approaches zero, wave crest pile up occurs
        
        large increase in the aerodynamic drag
        
        vs > v - supersonic
  - - - . The circular crests interfere constructively at points along the blue line
        
        this causes a very large amplitude crest – shock wave.
        
        sin a = vt / vst = v / vs
        
        v / vs is Mach Number