Sound - Volume

Objectives

To understand what steps are necessary to create louder and softer sounds.

To recognise that sound is measured in units called decibels (dB).

Resources

Lined paper | Variety of instruments to create loud and soft sounds | Smart phone or tablet with Decibel X: dB, dBA Noise Meter app downloaded

Today's Lesson

Main Activity

Before starting today’s lesson, you may wish to watch the following video which will introduce your student to the concept of volume.

Watch the video about the decibel scale and how the volume of sounds is measured.

A sound is louder when vibrations are bigger. Volume refers to how loud or soft a sound is. Sound volume is measured in decibels (dB) (named in honour of Alexander Graham Bell, who is credited with the invention of the telephone). A whisper measures around 15 decibels whereas a jet engine is around 150 decibels. Sounds louder than 85 dB can damage our ears.

Ask your child to think of how they could change the volumes of various sounds that they are able to create - for example, banging a drum harder or softer, shouting and whispering, increasing or decreasing the volume control on the TV or radio, and so on.

Ask your child to create a list of different sources of sound and of how to increase or decrease volumes of the same instrument.

For example:

human voice - can shout or whisper;
clapping - can pat hands gently or clap loudly;
drum - can be hit with hand or beater with varying intensity;
guitar or other musical instrument.

Think of some sounds you could make at home and measure e.g. clapping, blowing a whistle, running a tap. Predict which will be loudest or softest. How will you make the test fair? How will you record your results?

Download the app Decibel X: dB, dBA Noise Meter if you don’t already have it. This is a simple app to use, and it records sounds in decibels, displaying the recordings clearly on the screen. You can save the decibel recordings over time as line graphs (this is done automatically for you on the app as it records the sound).

Ask your child to experiment using the app and to get used to how it records sounds in decibels over time.

Then use the decibel scale below to discuss the different sounds and how many decibels they measure. It would be a good challenge to cover up three or four of the sounds, for example: rock band; normal conversation; whisper; and to ask your child to guess what the sounds are that are covered up, based on what sounds they can already see on the decibel scale.

Next, ask your child to measure some sounds using the decibel app.

Encourage them to draw up a chart of how they are going to measure the sounds, what sounds to measure, their predictions of decibel measurements and how to make the tests fair.

Ask your child to conduct the experiment and write up their findings.

Note: If you do not have a sound meter, your student could record the sounds as:

✔ = very soft

✔✔ = soft

✔✔✔ = loud

✔✔✔✔ = louder

✔✔✔✔✔ = loudest

Citations

[1] www.youtube-nocookie.com