Sound What is sound? Waves at boundaries Standing waves Harmonics The Doppler Effect Bow waves Shock waves

Thought to ponder: What causes a wave? Minute physics JOsiI

Hearing Test EsOI EsOI Mosquito Noise Test W1OhI00&feature=fvwp Another M

Sound – Wave Refresher Longitudinal Wave (Compression) Mechanical Wave – must have a medium Waves carry ENERGY st2d.html st2d.html st_hear.html st_hear.html

When do we use the term “Pitch” versus “frequency”? The highness or lowness of a sound wave – depends on frequency of vibration

Vocab review from yesterday As a team, using your whiteboard… Define, Illustrate and explain a real world application of the Doppler Effect?

The Doppler Effect The apparent change in frequency due to the motion of the source (or receiver) is called the Doppler effect. The faster the source moves, the greater the Doppler effect.

* Police measure a car’s speed by measuring the Doppler effect of radar waves.

unsw.edu.au/waves- sound/Doppler/index.html

In the pictures below, a bug makes ripples in the water. When the bug is moving, a receiver at point A would observe lower frequency. A receiver at point B would observe higher frequency.

The Doppler effect also occurs for light. An increase in frequency is called a blue shift, because the increase is toward the high-frequency, or blue, end of the spectrum. (light source approaching) A decrease in frequency is called a red shift, referring to the low-frequency, or red, end of the color spectrum. (light source receding)

Shock waves of Sound in Air

Bow Waves A bow wave is the v-shaped wave produced by an object moving faster than the wave being produced. A boat traveling faster than the speed of the waves it creates produces a bow wave. A bow wave is V-shaped and forms out to the side of the boat and continues until it strikes the shore.

Shock Waves A shock wave is a cone-shaped wave produced by an object moving at supersonic speed through a fluid (liquid or gas). A supersonic aircraft travels faster than the speed of sound, creating a shock wave behind it. When this layer of compressed air hits listeners on the ground, a sharp crack is heard called a sonic boom.

Shock waves of Sound in Air

Shock Wave AAYdbbc

Let’s Review: White boards and teams Tickets

What do you call a disturbance that can carry energy through matter?

What are the two categories or classifications of waves?

Which one does energy travel perpendicular to the medium?

Draw and label the parts of a transverse wave.

As wavelength increases what happens to the frequency?

Explain the difference between frequency and period. Include an illustration of each.

What is the relationship between frequency and period?

How do you determine the velocity of a wave? Include the equation and the definition (write out the words)

What is the unit for frequency?

What do you call a wave that transmits energy in the same direction as the wave or medium travels?

How high or low of a sound is called what? BE SPECIFIC.

Define the doppler effect and 1. Illustrate a source moving to the right 2. What would it look like if you were about to (but have not) broken the sound barrier?

What is the term to describe when two waves meet?

If a wave has a wavelength of 3 meters and it is traveling at 300 m/s, what is its velocity? Show work and include units

Illustrate the law of reflection Provide a definition

The image below is an example of what wave property?

What does the image below represent?

Battle of the Vocab! 2 minute limit

Sound Transmission Tuning Fork Demo Sound needs a medium: Medium can be: Gas (air), liquid, or solid Which would sound travel fastest through? Why?

Resonance Form of simple harmonic motion Occurs when small force is applied at regular intervals to an oscillating object and the amplitude of the vibration continues Examples: transfer of vibration to tuning fork; trampoline jumping; damage to stadium balconies; bridges collapsing

Tacoma Bridge Collapse

What happens when a wave changes mediums? When a wave pulse (the incident wave) reaches a boundary, it is partly reflected and partly transmitted. a) Part of the wave crosses the boundary as the “transmitted wave”. - same frequency - amplitude, wavelength, and speed change b) Part of the wave bounces off of the boundary as the “reflected wave”. - inverted if the second medium is more dense

Standing Waves A standing wave is the result of interference between the incident wave and its reflected wave.

In a standing wave certain parts of the wave, called nodes, remain stationary. The positions on a standing wave with the largest amplitude are called antinodes.

Harmonics: are waves that are whole number multiples of the fundamental. Have nodes at boundaries

Fundamental Lowest frequency of sound that will resonate

All other harmonics… Odd numbered multiple of the fundamental frequency. 50 Hz 2 nd harmonic = 100 hz 3 rd harmonic = 150 hz

The graphic below depicts the standing wave patterns for the lowest three harmonics or frequencies of a guitar string. A guitar string has a number of frequencies at which it will naturally vibrate. These natural frequencies are known as the harmonics of the guitar string.

Visualization of Harmonics VISUALIZING RESONANCE ml ml

Harmonics or Overtones

Pitch and frequency Qualitatively we have related wavelength on a string to a speed of string oscillation or frequency Qualitatively we have related the pitch we perceive to a frequency. PitchFrequencyWavelength Mode of oscillation