Chapter 10 Lesson 2, "Different Sounds"

Materials:

• Worksheet, 10-02, "Different Sounds"

Objective:

• Students will explain what intensity and volume of sound are.
• Students will explain how the frequency of a sound wave affects its pitch.

Anticipatory Set:* Students will be asked to describe 5 different sounds. moose, bear, chicken, cow, elephant, raccoon. The teacher will jot down key words in the descriptions for use later in the lesson.

Teacher Input:* Sound can be describe in two different ways the first is by how much energy sound has. This is called intensity. Define intensity and how it can be described by the sound wave. Show a man on a surfboard on a very high wave. Then show a man on a little wave. The man on the high wave has much more energy so you can think of this as INTENSE! when we measure the intensity of sound we measure the height of the sound wave. This can also be referred to as the amplitude of the wave. We measure the intensity on a scale we call decibels.

• Standard threshold of human hearing starts at zero,
• a whisper or a distance wind may have a level of about 10 decibels.
• A normal conversation is around 65 decibels.
• Driving a snow machinemy have 85-100 decibels. (Noise levels over 85 decibels can cause hearing loss)
• Shooting a gun can be as high as 120-150 decibels. Standing in front of the speaker system during a dance in the hall might get as high as 115 decibels.

The common name for the way intensity is measure by your brain is "Volume". Define Volume. Loudness of sound is not always a bad thing. Fire alarms need to be loud so they are heard by everyone. The alarm on the washeteria needs to be loud so that someone comes to see what is wrong, car alarms should be loud enough to scare off a would be thief.This by the way is a redneck's version of a car alarm. However, loud sounds can harm our hearing. any sounds over 90 decibels can cause us pain and sounds over 130 decibels can cause hearing loss some chainsaws reach this stage. Especially if they last for a long period of time.

The second way a sound can be measured is by pitch. Here is three different pitches. A piccolo can have the same intensity as a tuba but the tuba can play very low notes and a piccolo can play very high notes. To understand the difference we look at the sign curve of the sound wave. Both waves have the same amplitude but a high pitched sound has many more waves per inch of air than a low pitched sound so our ear drum is being vibrated much more quickly. The measure of the number of vibrations per second of a sound is the Frequency of sound. Define Frequency. The units of Frequency is the Hertz. This describes how many periods of compression are traveling through the air per second. From one period to the next is one cycle then we count how many cycles pass by a given point per second to get our Hertz. Define Hertz an Cycle.

Show a gong. Ask if you hit this softly and then hit it as hard as you can will the pitch be higher or lower the second time. The pitch of every object is based on the structure and size of the object. In this case you are only changing the intensity of the sound. It doesn't matter how hard you ring a bell, it always has the same pitch. Because of this there are limitations to how an object can be vibrated. If cycles are too close together or too far apart for instance they will not vibrate our ear drum no matter how intense they are. This is the same for all objects and animals. Look at this chart. You see that the eardrum of all these animals responds differently to different sounds.

Discuss the doppler effect using this picture and this sound.

Guided Practice:* Have the students answer the questions on Page 279 in class together.

Independent Practice:* Students will read lesson 2, Pages 275-278 and complete the worksheet, 10-02, "Different Sounds"

Check for Understanding:* Students will take the quiz, 10-02, "Different Sounds"

Duration:

30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).

Alaska Content Standards Addressed in this lesson:

• SCI A-1 Students will understand models describing the nature of molecules, atoms, and sub-atomic particles and the relation of the models to the structure and behavior of matter (Structure of Matter);
• SCI A-8 Students will understand the scientific principles and models that
  describe the nature of physical, chemical, and nuclear reactions;
  state that whenever energy is reduced in one place, it is increased somewhere else by the same amount; and
  state that whenever there is a transformation of energy, some energy is spent in ways that make it unavailable for use (Energy Transformations);
• SCI A-9 Students will understand the transfers and transformations of matter and energy that link living things and their physical

• SCI A-15 Students will use science to understand and describe the local environment (Local Knowledge); and: