What type waves are produced by the noise from a tuning fork?

Warm-UP: Complete KWL chart on Sound What do you know? What do you want to know? What do you want to learn?

• are waves produced by vibrating objects that travels through a gas, liquid, or solid.

• Are compression waves• Travel as vibrations moving through

the air as a compression wave• Travel through air, but travel through

other materials.• Slinky – example of compression

waves.

• What is an example of an animal that sends out sound waves under water?

• Whales communicate through long distances by producing sounds under water

2.1 Facts about Sound C-37- (P13IN)

Sound :• is a mechanical wave• is a vibration that travels through

gas, liquid, or solid p. C 40-41• is a longitudinal wave• transfers energy through a medium • speed depends on its medium p.C-42

How Sound Waves are Produced? C38

• Sound waves are produced by vibration that are usually too small to see.

• Vibrations push and pull on the medium around them

• Vibrations send waves out in all directions

• Vocal cords are sound making instruments in the body.

When are your vocal cords tensed up and when are they relaxed? P. C 39

• Vocal cords are tense when you are about to speak or sing.

• Vocal cords are relaxed when you are breathing to allow air to pass in and out of your windpipe.

• End of notes for 2.1

2.2 Frequency Determines PitchDescription of Pitch ( write on page 15)• the quality of highness or lowness• Is determined by frequency• A low-frequency makes a low pitch• A high frequency makes a high-pitch• Rapidly vibrating object makes a high

sound• Slowly vibrating object makes a low

sound

Which diagram represents:1. High Pitch? 2. Low PitchWasher (larger, small), ball, cork

A.

B.

Activity - Hit several objects against a tuning fork and try to identify the objects by sound [large and small washer, ping pong ball,& cork]

High and Low Frequencies

• Most humans with good hearing can hear in a range of 20 hertz to 20,000 hertz

• Elephants may use infrasound – sound that travels through the ground , hearing another elephant 20 miles away.

• Ultrasound is above 20,000 hertz and can be used for communication, find food, image internal body parts and detect objects

Natural Frequencies• A tuning fork has a natural

frequency and can be used to tune a piano

• Each musical instrument and each human voice has it own particular sound called sound quality or timbre

The Doppler Effect • Motion causes the sound you hear from

a passing vehicle such as a train to seemingly change its pitch (highness or lowness of sound).

• Frequency and Pitch• The sound from a fire truck that is far

away reaches you ear at a low frequency. When the vehicle is S, the frequency is greater and the pitch is higher.

End Notes for 2.2

15.2 The Doppler effect

• The shift in frequency caused by motion is called the Doppler effect.

• It occurs when a sound source is moving at speeds less than the speed of sound.

What is Resonance?

Many objects have a natural frequency – vibrates in a regular pattern. (swings and pendulums)

What is Resonance?

Many objects have a natural frequency – vibrates in a regular pattern. (see saw and pendulum)

Resonance occurs whenever a sound wave has the same frequency as the natural frequency of an object. The sound will cause the object with the same natural frequency to vibrate.

What is Resonance?

Many objects have a natural frequency – vibrates in a regular pattern. (see saw and pendulum)

Resonance occurs whenever a sound wave has the same frequency as the natural frequency of an object. The sound will cause the object with the same natural frequency to vibrate.

End Notes for 2.2

Sonic Boom

Read the caption on page C 44

The Look of SoundDigital Sampling of frequency from

sound waves

2.3 Intensity Determines Loudness

• Intensity Depends on the amplitude of a sound wave

• . As the amplitude of a sound decreases, the frequency stays the same.

• When you take away energy or add energy to a sound wave, you change its intensity without changing its quality

2.3 Facts about Amplification

• Amplification• Increases the strength of an electrical signal• Is often used to increase the intensity of a

sound wave• Is experienced when you listen to a TV, radio

or stereo

As an amplifier increases the sound, the amplitude of the wave increases.

One String Guitar

One String Guitar

Activity

Construct a single stranded guitar to determine which pitch is higher.Number each distance 1-3 using 1 =lowest , 2= medium 3 = highest?

________10 cm, _______ 15 cm or ______20 cm

Observe the vibration of the rubber band. At what distances are vibrations faster?

________10 cm, _______ 15 cm or ______20 cm

2.3 Main Idea about Acoustics

• Acoustics is the scientific study of sound• Acoustics

Involves how sound is producedInvolves how sound is received and heardRefers to the way sound waves behave

inside a place

2.3 Intense Sound Can Damage Hearing

• Intense sounds can damage and destroy hair cells inside the inner ear called the cochlear.• Hairs cells make hearing possible• Ear damage can be lessened by wearing ear plugs or covering the ear

Operation of the Cochlea

When vibrations form, sound waves enter the outer ear and then passes to the eardrum. The eardrum vibrates against the middle ear bones (hammer, anvil and stirrup) and is then transferred to the cochlear. Within the inner ear, there are tiny hairs that vibrate back and for with in the cochlear transmitting tiny electric signals to the braid.

Common Sounds and their Loudness

Using SoundWhat is Acoustics?

Acoustics is the study of sound and ways to optimize the hearing of sound inside various structures.

UCSD: Physics 8; 2006 29Spring 2006

Example Sound SpeedsMedium sound speed (m/s)

air (20C) 343

water 1497

gold 3240

brick 3650

wood 3800–4600

glass 5100

steel 5790

aluminum 6420

http://hypertextbook.com/physics/waves/sound/

Resources - http://www.proteacher.org/c/657_Light_and_Sound.html

Sound Waves

A sound wave is the result of vibrations producing alternating high-pressure and low-pressure regions of air.

A vibrating turning fork produces longitudinal waves.

OSHA Regulation – Exposure

140

120

100

80

Decibel 60

- Noise Control Program 40 - Hearing Conservation 20

0 2 4 6 8 Exposure Duration (Hours) End 2.3

notes

2.4 What is Echolocation?

When organisms send out ultrasound waves and then interpret the returning echo, it is called echolocation.

Uses of echolocation?

Dolphins and bats use echolocation to:

•hunt for food•Locate objects•Locate offspring and other like organisms

•Bats send out a chirp•Dolphins, toothed whales and porpoises send out ultrasound clicks or squeaks

What is sonar? Man uses the principle of echolocation called sonar.

Sonar is a system that uses the reflection of underwater sound waves to detect objects. This has been used to find sunken ships and schools of fish.

15.1 Recording sound

5. The electrical signal is amplified until it is powerful enough to move the coil in a speaker and reproduce the sound.

Sound waves are longitudinal Waves have compression (high) and rarefaction (low) areas of air pressure

Waves such as light, x-rays, and other forms of radiation do not require a medium.

Review

What are mechanical waves?

Mechanical waves are waves which require a medium. A medium is a form of matter through which the wave travels (such as water, air, glass, etc.)

Sound is a mechanical wave