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Sound - Volume
Objectives
To learn how to block sounds.
To recognise that sound is measured in units called decibels (dB).
Resources
Lined paper | Device to play music | Box to contain the musical device | Packing materials | Range of materials to try to soundproof the box e.g. egg trays, Styrofoam chips, rice, dried peas, newspaper, fabrics | Smart phone or tablet with Decibel X: dB, dBA Noise Meter app
Today's Lesson
Main Activity
Many sounds are extremely harmful to our ears.
Watch the video How to Muffle Sound.
The man in the video tried his best to block out the noises from his neighbours as he tries to get to sleep. ‘Muffle’ means to make sounds quieter. It is necessary to muffle sounds in lots of situations. People who work in noisy places often need to wear ear defenders e.g pilots of aeroplanes. Silencers are fitted to motor vehicles to silence the sound of their engines. Walls in houses and buildings are filled with material to minimise noise.
See if you can find out which material muffles sound best. Choose some materials. Items such as cardboard egg trays would be interesting to try, as well as Styrofoam chips, rice, or dried peas, newspaper, fabrics, and so on. Encourage your child to try to find some obscure and unusual materials to test!
Place a source of sound in the box (radio, phone playing music). Pack one of your chosen materials around the source of sound and close the lid. Stand 1m away and listen. Is the sound loud or soft? You could use the decibel recording app (downloaded in the previous lesson) to measure the sound volume and record it. Repeat the activity with more materials and present your results in a table.
Answer the scientific question: What is the best material to use to create soundproofing?
Elements of the investigation to make a fair test:
- Explain to your child that whenever a scientific investigation is set up and carried out in order to answer a question, you need to consider the variables that will make a difference to the results or data.
- In this case, the different materials that are used are predicted to make a difference to the volume of the sound that we will hear.
- Therefore, all other variables that could make a difference must stay the same - draw this out of your child’s understanding through discussion.
- Keep these variables the same: the volume the sound is set at whilst playing; the box the device is in; the distance the sound recorder (app on phone) is from the sound source; background sounds (ideally none).
- You may think of other, less important, variables with your child that could also make a difference.
Encourage your child to write up the experiment independently, explaining how to make the tests fair, and which materials muffled the sound well.