Ebook Sound

Physical Science by Timothy Sandow Genre Nonfiction Comprehension Skill Compare and Contrast Text Features · Captions · Labels · Diagram · Glossary Science Content Sound Scott Foresman Science 3.14 ì<(sk$m)=bdieha< +^-Ä-U-Ä-U Vocabulary compression wave pitch Sound by Timothy Sandow vibration Illustrations: 7, 14 Jeff Mangiat Photographs: Every effort has been made to secure permission and provide appropriate credit for photographic material. The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions. Unless otherwise acknowledged, all photographs are the property of Scott Foresman, a division of Pearson Education. Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R) Background (Bkgd) Opener: ©Jake Rajs/Getty Images; Title Page: ©DK Images; ©Lynn Stone/Index Stock Imagery; 2 ©Joseph Sohm/ChromoSohm Inc./Corbis; 4 (CL, BR) ©DK Images; 5 Getty Images; 6 Getty Images, 8 Getty Images; 9 (CL, CC, BL) Getty Images; 11 ©Robert Brenner/PhotoEdit; 12 ©P. Freytag/Zefa/ Masterfile Corporation; 13 ©Scott Tysick/Masterfile Corporation; 15 (CL) ©Mark Tomalty/Masterfile Corporation, (CC) ©Christiana Carvalho-Frank Lane Picture Agency/Corbis, (BR) ©DK Images, (BL) Stone/Getty Images ISBN: 0-328-13847-9 Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. This publication is protected by Copyright and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permissions, write to: Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025. 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05 What causes sounds? Take a walk in the city. Cities are noisy. Car horns honk. Buses and garbage trucks roar by. People talk on the street. It is much quieter in the country. Birds chirp. Cows moo. Water trickles in a creek. Sounds are everywhere. Some sounds you hear may hurt your ears. You may like other sounds. Each sound you hear is different. Sounds are also alike in some ways. Noisemakers are sometimes used on New Year’s Eve. Do you like the sounds they make? 2 3 The Causes of Sound Sound happens when matter moves back and forth very quickly. This movement is called a vibration. There must be movement to make sound. The instruments pictured make sounds. They can make high sounds. They can make low sounds. Pitch is how high or low a sound is. Objects that vibrate slowly make a low-pitched sound. Objects that vibrate quickly make sounds that have a higher pitch. You must hit or shake a tambourine to make a sound. Hitting or Plucking to Make Sound Some instruments make sounds when you hit them. They are called percussion instruments. Drums are percussion instruments. Drums are played with rubber hammers, wooden sticks, brushes, or your hands. If you tap a drum lightly, you hear a soft sound. Hitting the drum harder makes a stronger vibration. This makes a louder sound. The blocks on this instrument vibrate when they are hit with a rubber hammer. These drums are different shapes and sizes. Each one makes a sound with a different pitch when struck. 4 5 Stringed instruments are played in two ways. You can pluck the strings. Or you can rub a bow across them. Both ways make sounds. The strings are different sizes. They can be long or short and thick or thin. Some are stretched tighter than others. Long, thick strings make a lower-pitched sound. Short, thin, tight strings make faster vibrations. They make higher-pitched sounds. Using Air to Make Sound The sound of your voice is made by vibrations in your windpipes. When air from your lungs passes between your vocal cords, they vibrate. You can speak and sing because your vocal cords vibrate. When you speak, your cords tighten. The tighter they get, the higher the pitch of your voice. Your vocal cords are two pairs of thin tissue in your windpipe. Have you ever heard a harp before? The strings of this harp must be plucked to vibrate. 6 7 ... - tailieumienphi.vn