Everything Science Grade 10

10.4 CHAPTER 10. SOUND

Chapter 10 | Summary

See the summary presentation ( Presentation: VPecu at http://www.everythingscience.co.za)

• Sound waves are longitudinal waves


• Thefrequencyof a sound is an indication of how high or low thepitchof the sound
  is.


• The human ear can hear frequencies from 20 to 20 000 Hz. Infrasoundwaves
  have frequencies lower than 20 Hz.Ultrasoundwaves have frequencies higher than
  20 000 Hz.


• Theamplitudeof a sound determines itsloudnessor volume.


• Thetoneis a measure of thequalityof a sound wave.


• The speed of sound in air is around 340 m·s−^1. It is dependent on the temperature,
  height above sea level and the phase of the medium through which it is travelling.


• Sound travels faster when the medium is hot.


• Sound travels faster in a solid than a liquid and faster in a liquid than in a gas.


• Sound travels faster at sea level where the air pressure is higher.


• The intensity of a sound is the energy transmitted over a certain area. Intensity is a
  measure of frequency.


• Ultrasound can be used to form pictures of things we cannot see, like unborn babies
  or tumours.


• Echolocation is used by animals such as dolphins and bats to “see” their surroundings
  by using ultrasound.


• Ships use sonar to determine how deep the ocean is or to locate shoals of fish.

Physical Quantities

Quantity Unit name Unit symbol

Velocity (v) metre per second m·s−^1

Wavelength (λ) metre m

Amplitude (A) metre m

Period (T) second s

Frequency (f) hertz Hz (s−^1 )

Table 10.6: Units used insound

180 Physics: Waves, Sound and Light