CHAPTER 15. SOUND 15.3
proportions. The harmonics are determined by the standing waves that are produced in the
instrument. Chapter 16will explain the physicsof music in greater detail.The quality (timbre) of the sound heard depends on the pattern of the incoming vibrations, i.e. the
shape of the sound wave. Themore irregular the vibrations, the more jagged is the shape of the
sound wave and the harsher is the sound heard.15.3 Speed of Sound ESBGS
The speed of sound depends on the medium thesound is travelling in. Sound travels faster in solids
than in liquids, and faster in liquids than in gases. This is because the density of solids is higher than
that of liquids which means that the particles arecloser together. Sound can be transmitted more
easily.The speed of sound alsodepends on the temperature of the medium. Thehotter the medium is, the
faster its particles moveand therefore the quicker the sound will travel through the medium. When
we heat a substance, theparticles in that substance have more kinetic energy and vibrate or move
faster. Sound can therefore be transmitted more easily and quickly in hotter substances.Sound waves are pressure waves. The speed ofsound will therefore beinfluenced by the pressure of
the medium through which it is travelling. At sealevel the air pressure is higher than high up on a
mountain. Sound will travel faster at sea level where the air pressure is higher than it would at places
high above sea level.DEFINITION: Speed of sound
The speed of sound inair, at sea level, at a temperature of 21◦C and under normal
atmospheric conditions,is 344 m·s−^1.Exercise 15 - 1
Study the following diagram representing a musi-
cal note. Redraw the diagram for a note- with a higher pitch
- that is louder
- that is softer
More practice video solutions or help at http://www.everythingscience.co.za(1.) 00sj (2.) 00sk (3.) 00sm
See video: VPkxq at http://www.everythingscience.co.za