Waves and Sound - PowerPoint PPT Presentation

Loading...

PPT – Waves and Sound PowerPoint presentation | free to download - id: 7ad985-OGYzM



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Waves and Sound

Description:

Waves and Sound Honors Physics Chapter 14 – PowerPoint PPT presentation

Number of Views:55
Avg rating:3.0/5.0
Slides: 37
Provided by: miss1150
Category:
Tags: sound | wave | waves

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Waves and Sound


1
Waves and Sound
  • Honors Physics
  • Chapter 14

2
Definition of a wave
  • A disturbance that propagates from 1 place to
    another.
  • Characterized by a large transfer of energy
    without a large transfer of medium

3
Types of waves
  • Mechanical waves require a medium (air, water,
    ropes) to travel
  • Electromagnetic waves do not require a medium to
    travel (light, radio)
  • Matter waves produced by electrons and particles

4
Mechanical Waves
  • Transverse the displacement of the individual
    particles is perpendicular to the direction of
    propagation.

5
Mechanical Waves
  • Longitudinal The displacement of the individual
    particles is parallel to the direction of
    propagation.

6
Mechanical Waves
  • Surface waves the displacement of individual
    particles is circular (result of both transverse
    and longitudinal motion)

7
Waves in motion
  • Longitudinal and Transverse Wave Motion

8
Properties of waves
  1. Amplitude (A) the maximum displacement from
    equilibrium position, measured in meters.
  2. Wavelength ( ?) the distance between 2 particles
    that are in phase with each other, measured in
    meters.

9
Wave diagram (link)
10
Properties of waves
  • 3. Frequency (f) number of complete waves that
    pass a point in one second, measured in 1/seconds
    or Hertz (Hz)
  • 4. Period (T) the time it takes for one complete
    wave to pass a given point, measured in seconds.

11
Properties of waves
  • Velocity of propagation (v) horizontal speed of
    a point on a wave as it propagates, measured in
    m/s.

12
Relationships/equations
  • T 1/ f
  • or f 1/T
  • v f ?

13
Phase
  • In-phase when waves are synchronized (crest
    meets crest)
  • Out-of-phase waves are not synchronized
  • Opposite phase (180º out-of-phase) crest meets
    trough

14
Reflections
  • Fixed End
  • Explanation
  • Animation
  • Open End
  • Explanation
  • Animation
  • Between different mediums scroll down (What do
    you notice about the phases? Transmitted?
    Reflected?)

15
Principle of Superposition
  • Occurs when two waves travel through the same
    medium at the same time.
  • Each wave affects the medium independently.
  • The displacement of the medium is the algebraic
    sum of the displacements.
  • Animation

16
Interference
  • Constructive occurs when wave displacements are
    in the same direction (in-phase)
  • Destructive occurs when wave displacement are in
    different directions (out-of-phase)
  • Animation(try at home)

17
What is Sound?
  • Longitudinal
  • Mechanical (link)
  • Rarefaction low air pressure
  • Compression high air pressure
  • module (sources of sound)

18
Speed of sound
  • Depends on
  • Temperature
  • V air 331m/s (0.6 m/s/ºC)T
  • Density/kind of medium
  • Gases ltliquidsltsolids
  • Chart of speeds

19
Speed of sound
20
Pitch
  • How we perceive variations in frequency
  • Audible range 20-20,000 Hz (listen)
  • Infrasonic vs. ultrasonic
  • Most sensitive to 1,000 to 5,000Hz
  • Loudness can distort our perception of pitch
    (listen tape)
  • Module (pitch)

21
Doppler Effect
  • Variation in the frequency of sound due to the
    relative motion of the sound source or the
    listener.
  • Animation1 (try at home)
  • Picture of a sonic boom
  • Video of sonic boom
  • mythbuster

22
Doppler Effect Results
  • As an moving sound source approaches a listener
    the frequency (pitch) increase.
  • As a moving sound source passes by a listener the
    frequency (pitch) decreases.
  • Same effect if sound source is stationary and
    listener is moving.

23
Calculating Frequency change
  • f f (v vR / v vs)
  • f new frequency
  • f original frequency of source sound
  • v velocity of sound
  • vR velocity of receiver
  • vs velocity of source

24
Loudness
  • How we perceive variations in amplitude and
    intensity.
  • Module (loundness)
  • In general, sound waves of higher intensity sound
    louder but we are not equally sensitive to all
    frequencies.

25
Sound Intensity
  • The amount of energy that passes through a given
    area in a given time.
  • IP/A
  • Ppower (watts)
  • A area (m2)
  • I intensity (W / m2)
  • Directly proportional to the square of the
    amplitude.
  • Inversely proportional to the square of the
    distance from the source.

26
Relative Intensity
  • Logarithmic scale used to indicate the intensity
    level of a sound.
  • Measured in decibels or dB
  • ß 10 log (I / Io)
  • Io 110-12 W/m2 (intensity of the faintest sound
    that can be heard)
  • I intensity of sound in W/m2

27
How loud is a decibel?
  • Threshold of hearing( Io ) 0dB (air pressure
    210-5 Pa)
  • Threshold of pain 120 dB (air pressure 20 Pa)
  • We perceive a 10 dB increase as twice as loud.
  • Every 20 decibels air pressure increases 10 times
  • Table of sound levels

28
Resonance
  • Causing the vibration of an object by the
    influence of another vibrating body.
  • Must match the natural frequency of vibration of
    the object
  • Whole-number multiple of the natural frequency
    work too.
  • Breaking a glass with resonance

29
Standing waves
  • Caused by the interference of reflected waves
    with incident waves from the source.
  • Nodes pts of no displacement
  • Antinodes pts of maximum displacement
  • Applet (try at home)

30
Vibrating Columns of Air
  • Column will emit a sound when the air inside
    achieves resonance.
  • DEMO (cardboard moose call)
  • Frequency of vibration depend on
  • Length of column
  • Type of column
  • Open end
  • Closed end

31
Fundamentals and Harmonics
  • Fundamental Frequency lowest frequency of
    vibration
  • Harmonics whole number multiples of the
    fundamental
  • Note the fundamental frequency is the 1st
    harmonic.
  • Animation

32
Calculations for closed pipe
  • Fundamental frequency
  • f1 v /4L (Llength of air column)
  • Harmonics
  • fn nf1 (n1,3,5,)
  • ? 4L/n
  • Note only ODD harmonics are produced
  • Animation

33
Closed (at one end) pipe
  • The standing wave created has
  • Node at closed-end
  • Antinode at open-end

A
N
34
Open pipe
  • The standing wave created has
  • Antinode at both ends

A
A
35
Calculations for open pipe
  • Fundamental frequency
  • f1 v /2L (Llength of air column)
  • Harmonics
  • fn nf1 (n1,2,3,)
  • ? 2L/n
  • Note ALL harmonics are produced
  • animation

36
Frequency
  • Light
  • Sound (listen)
  • BACK
About PowerShow.com