Sound (continued)
Overview
Thunder rolls in seconds after the lightning flash, a shout returns as an echo from a cliff, and an unborn baby is imaged with sound too high-pitched to hear. Sound is a wave that travels through matter, and by timing it, reflecting it and pushing its frequency above hearing we can measure distances, find flaws and see inside the body.
In this lesson you will measure the speed of sound in air from a distance and a time, describe how amplitude and frequency set the loudness and pitch of a note, define an echo and ultrasound, and use ultrasound in sonar and scanning, including calculating depth or distance from the travel time and the wave speed.
Objectives
- Describe a method involving a measurement of distance and time for determining the speed of sound in air
- Describe how changes in amplitude and frequency affect the loudness and pitch of sound waves
- Describe an echo as the reflection of sound waves
- Define ultrasound as sound with a frequency higher than 20 kHz
- [Supplement] Describe the uses of ultrasound in non- destructive testing of materials, medical scanning of soft tissue and sonar including calculation of depth or distance from time and wave speed
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Lesson Evaluation
Congratulations on completing the lesson on Sound (continued). 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.
- The approximate speed of sound in air is A. 3 m/s B. 34 m/s C. 340 m/s D. 3 x 10^8 m/s Answer: C
- Increasing the amplitude of a sound wave increases its A. pitch B. frequency C. loudness D. speed Answer: C
- Ultrasound is defined as sound with a frequency higher than A. 20 Hz B. 200 Hz C. 2 kHz D. 20 kHz Answer: D
- An echo returns from a wall 1.0 s after a clap. The wall is 170 m away. The speed of sound is A. 85 m/s B. 170 m/s C. 340 m/s D. 680 m/s Answer: C
- A sonar pulse takes 0.4 s to return from the seabed (speed 1500 m/s). The depth is A. 150 m B. 300 m C. 600 m D. 1200 m Answer: B
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Recommended Books
Further learning from open sources
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Textbook section
Ultrasound
Any sound with a frequency above 20,000 Hz (or 20 kHz)—that is, above the highest audible frequency—is defined to be ultrasound. In practice, it is possible to create ultrasound frequencies up to more than a gigahertz. (Higher frequencies are difficult to create; furthermore, they propagate poorly b
"College Physics: Ultrasound" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/17-7-ultrasound. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
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Textbook section
Sound Intensity and Sound Level
Relate amplitude of a wave to loudness and energy of a sound wave
"Physics: Sound Intensity and Sound Level" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/physics/pages/14-2-sound-intensity-and-sound-level. Access for free at https://openstax.org/books/physics/pages/1-introduction
Published by other organisations under open licences, credited as they ask. Links open their websites.
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