Science - Combined - 0653 CIE

Sound

Overview

Pluck a guitar string, hit a drum or speak, and something vibrates. That vibration pushes on the air, and a wave of squeezes and stretches travels outward until it reaches your ear. Sound is a wave you can hear, but only within a certain range of frequencies and only when there is material for it to travel through.

In this topic you will describe how sound is produced by vibrating sources, learn that sound is a longitudinal wave made of compressions and rarefactions, and meet the range of frequencies humans can hear. You will also learn why sound needs a medium, how fast it travels in air, and why it travels faster in solids than in liquids or gases.

Objectives

[Core] Describe the production of sound by vibrating sources
[Core] State the approximate range of frequencies audible to humans as 20 Hz to 20 kHz
[Core] Know that a medium is needed to transmit sound waves
[Core] Determine the speed of sound in air using a method involving a measurement of distance and time
[Core] Describe how changes in amplitude and frequency affect the loudness and pitch of sound waves
[Core] Describe an echo as the reflection of sound waves
[Core] Define ultrasound as sound with a frequency higher than 20 kHz
[Supplement] Describe the longitudinal nature of sound waves in air as a series of compressions and rarefactions
[Supplement] Describe, qualitatively, compressions as regions of higher pressure due to particles being closer together and rarefactions as regions of lower pressure due to particles being spread further apart
[Supplement] Know that, in general, sound travels faster in solids than in liquids and faster in liquids than in gases

Lesson Note

Sound underlies speech, music, sonar, ultrasound scans and noise control. Understanding that it is a longitudinal wave that needs a medium explains why there is silence in space and why you hear an approaching train through the rail before the air. Exam questions test the production, nature, speed and audible range of sound.

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Lesson Evaluation

Congratulations on completing the lesson on Sound. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

A sound wave is best described as: A. a transverse wave B. a longitudinal wave C. an electromagnetic wave D. a stationary wave Answer: B
The approximate range of frequencies audible to humans is: A. 2 Hz to 2000 Hz B. 20 Hz to 20 000 Hz C. 200 Hz to 200 000 Hz D. 0 Hz to 100 Hz Answer: B
Sound travels fastest in: A. a gas B. a liquid C. a solid D. a vacuum Answer: C
An echo returns from a wall 510 m away in 3.0 s. The speed of sound is: A. 170 m/s B. 340 m/s C. 1530 m/s D. 255 m/s Answer: B
A region of a sound wave where particles are pushed together is a: A. rarefaction B. crest C. compression D. trough Answer: C