Waves and sound

• Vibration is a type of cyclical motion about an equilibrium point

  • One path traveled/ cycle. is calculated through $di=$$df$
• A medium is a material that can be either solid liquid or gas
• Mechanincal wave is the transmission of energy as particles vibrate.

  • Fastest in solid (densely packed), slowest in gas
• Transverse wave are particles that vibrate perpendicular to direction of flow

  • Particles move up and down
  • Energy moves left and right
  • E.g light; Doesn't need a medium
• A longitudinal wave are particles that move parallel to direction of flow

  • Particles move side to side
  • energy moves up and down
  • E.g sound; NEEDS A MEDIUM
• Compression is a region in longitude wave where particles are closely packed together
• Rarefaction is a region in longitudinal wave where particles are far apart
• Sound is a pressure wave; it pushes molecues in the air together (compression)
• A wave is a disturbance that travels through a medium
• A waveform is defined to be a waves shape when graphed
• Waves are presented as sinusoidal (starts from 0) or cosinusoidial (doesn't start at 0)
• • Amplitude is the maximum displacement of a wave from its equilibrium point
  • Crest is the location of the waves maximum point: Amax
  • Trough is the mimum point of wave from equilibrium: Amin
• Name the parts of the wave

  A) crest

  B) Amplitude

  C) wavelength

  D) Trough

  E) equilibrium

  
• The frequency and period of a wave are related by f=1/T
• Wavelength: the distance between 2 similar points on a wave form

  • Crest to crest
  • Trough to trough
• Phase= x coordinate of any unique point
• Phase Shift: horizontal shift of the ENTIRE wave along the x axis
• Label wither the grapgh is IN pase or OUT phase

  A) OUT

  B) IN

  
• Period (T)= time taken for one complete cycle
• Frequency(f)= number of cycles per second
• Frequency is measured in hertz or $S^-1$
• Frequency and period are reciprocols of one another: $f=$$1/T$
• An Increase in temperature in a medium increases the speed of wave
• Linear density

  • scalar
  • kg/m
  • mu
• As linear density of a string increases, the speed travelling along the wave decreases

  • String has more inertia; more energy required to vibrate the string
• The molecules of a string are pulled apart as force is exerted along the string

  • Causes it to restore the system back to equilibrium
• As tension Increases, the speed of traelling waves in a rope or string increase
• Force of Tenion

  • Newtons
  • Restoring force that attempts to bring the system back to equilibrium
• Humans can hear between 20 Hz to 20,000 hz
• Sounds with frequency below 20 Hz is called infrasonic waves
• Sound waves over the frequency f 20,000 Hz are called ultrasonic
• Ultrasound waves produce images

  • non-ionizing meaning they don't break chemical bons making it the very safe for mother and child
• Speed of sound depends on temperture
• Mach number; ratio of airspeed of an object to the local speed of sound

  • scalar
  • speed/speed
• Mach 1 is the speed of sound.
• Sound intentisy; amount of power pwer unit area

  unit is Watts / M^2
• Decibel scale: compares relative intensities of different sound waves

  • Units: dB
  • Decibel is a logarithmic scale; every step up is x 10
  • every increase in 10 dB represents an increase in sound intensity by a factor of 10
• Threshold of human hearing has an intesnity of 10^-12 w/m^2
• human sound threshold is 0 dB
• Interference: when two or more waves meet at the same region and generate a new wave