Sound Chapter 12 Lesson 2

Sound Stay quiet for 30 seconds. Write the sounds you hear. ___________________

How is sound produced? When an object makes sound, it vibrates back and forth. Define compression – regions of air that have many particles. Define rarefactions – regions of air that have few particles.

Sound Wave

How is sound produced? Define sound wave – a series of compressions and rarefactions traveling through a substance. Demonstration #1: Let’s model how a sound wave works.

How is sound produced?

ed.org/EducationResources/HighSchool/Sound /Popup/discussion002.htm C8 s/wavemotion.html

How is sound produced? Define medium – a substance through which a sound wave travels. When sound waves pass through a medium, which could be a solid, liquid or a gas the medium does not move, but the sound energy moves from one place to another.

On your Own Reading page 639 – Paragraph #2 In what direction do the sound waves vibrate the medium? Sound waves vibrate through the medium in the same direction the energy moves. Define longitudinal waves – waves that vibrate the medium in the same direction that the energy moves. When sound waves hits an object it can start vibrating. The object can move by the energy of the wave.

How does Sound Travel? Define vacuum – a region that contains few or no particles. Why can’t we hear a radio in space? Because there is no medium for sound to travel through

How does Sound Travel? Sound travels fastest in solids and slowest in gases. The difference in how fast sound travels through substances are due to how far apart the particles are. In solid substances the particles are very close together so they collide quickly and move sound rapidly.

Demonstration #2 Sound traveling through a solid. Ms. Roth taps on the outside wall. Could you hear clearly through this solid? How many times did she tap?

Demonstration #3 Listening to tapping through a solid. Students will put one ear on the table top and tap a pencil on the table. Then sit up and tap a pencil on the table top again. Which sound was louder, through the solid table or through the air? Sound travels better through a solid than through air, which is a gas because the particles in the solid are closer together.

Demonstration #4 Sound waves move through a liquid. Ms. Roth will hit a tuning fork and put it into a shallow pan of water. What did you see? What caused this?

Demonstration #5 Hearing sound through water. Hold the bag of water 5 inches from your partner’s ear. Tap on the bag. Now place the bag directly on your partner’s ear. Tap again.

Demonstration #5 Was the sound louder when bag was touching or not touching the ear? Through what medium did the sound travel when the bag was held away from the ear? Through what medium did the sound travel when the bag was against the ear? Conclusion: Sound travels best through a solid substance, second best through a liquid substance, and least through a gas substance.

How sound travels? Temperature of the medium affects the speed of sound. In warm air the particles collide more often so they transmit the sound faster.

How sound travels? When sound hits thick, soft, or uneven materials, the sound is absorbed by that substance. Name some substances in our classroom that absorb sound energy well. ___________________

How sound travels? When sound waves hit a flat, firm surface they reflect back causing an echo. – What area of the school creates the best echo? Gym – Why? No sound absorbers except the mats. Even though we hear an echo, some of the sound energy is absorbed, so even when sound waves reflect off a surface, some sound is absorbed.

What is pitch? Define frequency – the number of times a sound wave vibrates in one second. High frequency sounds have crests close together like this:

What is pitch? Low frequency sounds have crests farther apart like this:

What is pitch?

Define pitch – the high or low tone. A series of eight notes is called a(n) octave.

What is pitch? Math Link: The frequency doubles for every octave. The first “C” note on the piano is 55 Hz. The second “C” note on the piano will be ______Hz. The third “C” will be _________ Hz. The frequency doubles for each higher octave.

What is pitch? Solve: If the frequency for the 1 st “A” note is 33Hz, what is the frequency for the 6 th “A” note? ________________

Demonstration #6 Go to the back of the class to observe demonstration for today. Fill in the blanks for Demonstration #6 and numbers DO NOT GO PAST NUMBER 9!!

Doppler Effect Doppler Effect – it is a change in frequency due to moving away or toward a sound wave. An example of a Doppler Effect is the train whistle. As the train moves towards you, the sound is higher than normal. As the train moves away from you the sound is lower than normal.

Doppler Effect

What is volume? Define amplitude – the height of a sound wave. It is the strength of the wave. Scientists measure the volume of sound in decibels (dB). A 20 dB noise has 10 times more energy than a 10 dB noise. Any sound above 85 decibels will damage your hearing.

Decibel Level Decibel levelSound 180 dBRocket Engine from a 100 feet away 130 dBThreshold of pain, train horn 10 feet away 120 dBRock Concert 110 dBChain saw 3 feet away 100 dBJackhammer at 6 feet away 85 dBThreshold of damaging hearing 80 dBVacuum cleaner 3 feet away 60 dBNormal Conversation 50 dBRainfall 30 dBWhisper in a quiet library 10 dBHuman breathing 10 feet away 0 dBThreshold of human hearing with healthy ears.

What is volume oudness.html oudness.html

Sounds Adults Can’t hear

What is echolocation Define echolocation – finding an object by using reflected sound. Name three animals mentioned in the book that use echolocation to find food. Bats Whales Dolphins

What is echolocation? Bats make sounds. These sound bounce off an insect and back to the bat. The bat follows the path of the waves to locate the insect so it can eat it.

What is echolocation

What is echolocation? The SONAR system is used underwater by scientists. The SONAR sends out sound waves that reflect off an object. The amount of time it takes for the sound to return helps calculate the location of the object. SONAR could work on land too because sound travels through a solid. Ultrasounds work like SONAR and is a technology used in medicine.