What you’ll learn12 learning objectivesChoose one objective for a focused lesson, or study the complete topic.3.4.1Production of sound by vibrating• Describe the production of sound by vibrating sourcesSyllabus objective3.4.2Longitudinal nature of sound waves• Describe the longitudinal nature of sound wavesSyllabus objective3.4.3Approximate range of frequencies• State the approximate range of frequencies audible to humans as 20 Hz to 20 000 HzSyllabus objective3.4.4A medium is needed to transmit sound• Know: a medium is needed to transmit sound wavesSyllabus objective3.4.5Speed of sound in air is approximately• Know: the speed of sound in air is approximately 330–350 m/sSyllabus objective3.4.6Method involving a measurement of• Describe a method involving a measurement of distance and time for determining the speed of sound in airSyllabus objective3.4.7Changes in amplitude and frequency• Describe how changes in amplitude and frequency affect the loudness and pitch of sound wavesSyllabus objective3.4.8An echo as the reflection of sound• Describe an echo as the reflection of sound wavesSyllabus objective3.4.9Ultrasound as sound with a frequency• Define ultrasound as sound with a frequency higher than 20 kHzSyllabus objective3.4.10Compression and rarefaction• Describe compression and rarefactionSyllabus objective3.4.11That, in general, sound travels faster• Know that, in general, sound travels faster in solids than in liquids and faster in liquids than in gasesSyllabus objective3.4.12Uses of ultrasound in non- destructive• 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 speedSyllabus objective