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The noisy reef takes us under the waves to the reefs of New Zealand to explore sound and noise under water. Using this unique habitat, we look at what sound is, how it travels, what changes under water and how animals use sound in their world. Find out more about studying sound under water.

A key idea is that animals can use the sounds of the reef to navigate. Fish and crab larvae floating in currents several kilometres from shore need to find their way back to the reef before they settle and metamorphose into the adult form. We know that smell and light are important in this process, but for the first time, New Zealand scientists Associate Professor Craig Radford and Dr Jenni Stanley have evidence that sound is also used as a navigation tool. Larval crabs are attracted to the sound of a healthy reef and will use this to find their way home.

We also explore what makes a reef such a noisy place. You can probably think of some factors – waves and wind – but the scientists we talk to also listen to kina, shrimp and fish such as John Dory. In the article New Zealand reef noise, learn more about phenomena such as the ‘evening chorus’ – the name for the cacophony of sounds that come from a reef around dusk. Kina make much of this noise, but how do they do it, and how does the sound travel?

Key science concepts

The concept of a noisy reef can be used to explore a range of physical concepts including the basics of sound. Scientists like Professor John Montgomery talk about how they use physics as a tool to understand a biological system. It is important that they understand the basics of sound waves, how sound travels through water, how animals hear sound and whether larval animals could actually hear the reef.

Additional science concept articles include measuring sound (along with an animated sound wave ripple pattern), hearing (in humans and in other animals) and why scientists use models.

More than just physics

While learning about the physics of sound, take some time to explore biological concepts like habitat and reef zones in Life on a reef. Then test your knowledge by building an ideal marine habitat with the interactive Home for a crab.

Take up the challenge

Using the idea of the reef and navigation, our resources explore some essential physics ideas relating to sound, but in a whole new way. Student activities include:

Modelling waves with slinkies – stay indoors and model how sound travels.

Catching worms using ground sounds – go outdoors and investigate whether there is any evidence that earthworms respond to vibrations in the ground.

Sound detectives – can you locate sounds while blindfolded?

How small is that? – fill a matchbox with tiny items to model the tiny size of a crab and the huge distances they navigate to find their way back to their reef.

Creating soundscapes – discover how background sound differs from one geographical setting to another.

Make and use a hydrophone – and listen to underwater sounds.

Sound on an oscilloscope – use oscilloscope software and your computer to make and watch a visual sound display.

Hearing sounds under water – go underwater yourselves to listen to sounds.

Question bank

The The noisy reef – question bank provides an initial list of questions about how underwater animals use sound in their world and indicates where their answers can be found. The questions support an inquiry approach.

Key terms

For explanations of key concepts, see The noisy reef – key terms.

Timeline

Explore the timeline and find out more about some important dates relating to key developments in underwater acoustics.

    Published 10 May 2011 Referencing Hub articles