{ Chapter 2: Sound Section 1: The Nature of Sound

1. Fill a bowl with water 2. Tap a tuning fork against the sole of your shoe. Place the tip of one of the prongs in the water. What do you see? 3. Tap the tuning fork again. Predict what will happen when you hold it near your ear. What do you hear? 4. Observations: How are your observations related to the sound you hear? What might change if you use a different tuning What might change if you use a different tuning fork? fork? Discover Activity: What is Sound

I. Sound Waves: A. Sound: A. Sound: is a disturbance that travels through a medium as a longitudinal wave. 1. Making Sound Waves: a. A sound wave begins with a vibration Ex: striking a gong, the vibrations disturb the surrounding air particles

2. How Sound Travels a. sound waves carry energy through a medium medium b. You hear sound when the disturbance b. You hear sound when the disturbance hits your ears hits your ears c. Air is the common medium for sound d. Solids and liquids act a mediums too Ex: Knocking on a wood door wKI

e. Sound is three dimensional II. Interactions of Sound waves A. Sound waves reflect off objects, diffract A. Sound waves reflect off objects, diffract through narrow openings and around barriers, through narrow openings and around barriers, and interfere with each other. and interfere with each other. 1. Reflection: Echo: a reflected sound wave a. Harder and smoother surfaces reflect stronger sounds waves Ex: clapping in a gym vs. living room

2. Diffraction: Ex: hearing classmates in a classroom before you Ex: hearing classmates in a classroom before you see them see them a. Sound waves can spread out after passing through a doorway, and can bend around a through a doorway, and can bend around a corner. corner. 3. Interference: a. sound waves have two types of interference a. sound waves have two types of interference 1. constructive 1. constructive 2. destructive 2. destructive

III. The Speed of Sound A. Sound waves travel at different speeds in A. Sound waves travel at different speeds in different mediums different mediums Ex: at 20 degrees C sound travels through Ex: at 20 degrees C sound travels through air at 343m/s air at 343m/s B. The speed of sound depends on the elasticity, B. The speed of sound depends on the elasticity, density, and temperature of the medium the density, and temperature of the medium the sound travels through sound travels through airplane reaches “supersonic” airplane reaches “supersonic” happens-when-an-airc/ happens-when-an-airc/

1. Elasticity: the ability of a material to bounce back after being disturbed bounce back after being disturbed a. The more elastic a material the faster sound travels in it sound travels in it 1. sounds travel better in solids that are more 1. sounds travel better in solids that are more elastic than liquids or gases elastic than liquids or gases

2. Density: 2. Density: A. Density A. Density- how much matter, or mass, there is in a given amount of space, or volume 1. sound travels more slowly in denser mediums Ex: silver and lead slower than iron or steel Ex: jewelry inspired by sound waves

3. Temperature: 3. Temperature: A. Sound travels more slowly at lower temperatures than at higher temperatures than at higher 1. due to particles moving more slowly at lower temp’s lower temp’s 2. higher altitudes = sound traveling slower slower a. This is why the early pilots flew their planes high to break the their planes high to break the speed of sound speed of sound