WOULU
E Jungle life is full of movements and sounds of animals and birds. Find as many words as you
can from the extract that relate to:
Sound:
Movement
Answers
Explanation:
Sound is all about vibration. To make a sound, something has to vibrate — whether that’s the string of a guitar, the larynx (voice box) of a person, or the loudspeakers of your radio. Sound waves consist of vibrating particles, which knock into other particles, causing those particles to vibrate and knock into more particles, and so on and so forth; this is how sound waves travel away from their source. We hear sounds because the vibrations in the air cause our ear drums to vibrate, and these vibrations are converted into nerve signals that are sent to our brains. Similarly, microphones detect vibrations in the air and convert them into electrical signals.
When you imagine a sound wave, you might think of something that looks a bit like a water wave:
A cosine wave
However, this isn’t really an accurate representation of a sound wave. The particles that vibrate as part of a sound wave move back and forth along the axis along which the sound wave is travelling. This movement creates areas where particles are more bunched up (areas of high pressure, or compressions) and areas where particles are more spread out (areas of low pressure, or rarefactions). This type of wave is called a longitudinal wave.
It’s not easy to visually represent a longitudinal wave; there are two types of graphs to do it:
A graph like the one below, where the x-axis indicates space, with the top of the wave representing areas of compression, and the bottom of the wave representing areas of rarefaction
A graph where the x-axis indicates time, so the graph represents a sound wave passing a particular point in space; this is the more commonly used type of graph
At the top, a set of dots representing particles. The concentration of these changes periodically from left to right. Below this is a graph with the x-axis labelled Distance and a y-axis labelled Pressure. The graph shows a sinusoidal wave with peaks aligned below the regions with the highest concentration of dots, and troughs aligned below the regions with the lowest concentration of dots.
Amplitude and frequency
Want to keep
learning?