What it shows
A funnel and a rubber tube can carry the sounds of the heart to your ear. You hear a steady lub-dub that is made as the heart valves close.
The science
The heart is a muscular pump with four chambers and valves. The first sound, lub, comes as the valves between the upper and lower chambers close when the lower chambers squeeze. The second, dub, comes as the valves leaving the heart close at the end of the squeeze. A funnel gathers the weak sounds, and the tube guides them to the ear instead of letting them spread in the air. The same idea is used in a doctor’s stethoscope.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A small plastic funnel
- About 50 cm of soft plastic or rubber tube that fits the funnel
- A balloon cut open for a thin membrane (optional)
- A rubber band
- A watch for counting
- Soapy water and a clean cloth
- A friend or family member
Safety
For this project: An adult must help to fit the tube. Keep the sounds soft, never blow into the tube, and clean the funnel with soapy water between users.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Stretch a piece of balloon rubber over the wide mouth of the funnel and hold it with a rubber band, if you want a thin membrane.
Push the narrow end of the funnel into one end of the tube and make it fit tightly.
Place the other end of the tube gently at the opening of your ear and sit quietly.
Press the funnel lightly on the left side of a friend’s chest, a little below the nipple line, over their clothes, and keep still.
Listen for the lub-dub sound and count the number of "lub" sounds in 30 seconds, then double it.
Try the funnel at other places on the chest and note where the sound is loudest.
Listen again after the friend has done 20 jumps and count the beats once more.
Draw the heart on a card, label the chambers and valves, and mark which valves make each sound.
What you should see
You hear a regular lub-dub, about 70 to 100 times a minute at rest, louder at the left side of the chest. The sound is faster after jumping.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What makes the lub-dub sound?
The closing of the heart valves.
2Why does the tube help hearing?
It guides the sound to the ear instead of letting it spread out.
3How many chambers does the human heart have?
Four.
4Why is the heartbeat faster after exercise?
The muscles need more oxygen, so the heart pumps faster.
Take it further
Record heartbeats per minute for several family members at rest and see how age and fitness relate to the rate.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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