What it shows
Sound from the heart is passed through the chest and can be gathered by a cup, which makes it louder in your ear. Counting the beats gives the heart rate.
The science
The heart makes a "lub-dub" sound when its valves close. The sound travels through the body as small vibrations. The cup funnels these vibrations into the tube and so into the ear, instead of letting them spread in all directions. A hollow tube keeps the sound from fading.
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 paper cup or a funnel
- A rubber tube or a 30 cm piece of clean plastic tubing
- Tape
- A stopwatch
- A cloth for cleaning
- A friend
Safety
For this project: Use quiet, gentle pressure on the chest. Wipe the funnel with a clean cloth between users. This model is not a medical tool and cannot be used to check health.
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.
Cut the bottom of the paper cup if needed so that the narrow end fits the tube.
Tape the tube firmly to the cup narrow end so that no sound leaks out.
Place the open end of the cup on a friend’s chest on the left side, over their clothes.
Hold the end of the tube close to your ear and keep very quiet.
Listen for the repeated "lub-dub" sound and count the beats for 30 seconds.
Double the count to get beats per minute, and compare with the wrist pulse count.
Listen again after your friend hops for one minute and note the change.
Draw a picture of the heart and write what makes the lub and what makes the dub.
What you should see
A cup stethoscope that makes heart sounds easier to hear, with a beat count that matches the pulse at the wrist, and a faster rate after hopping.
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?
Heart valves closing as blood moves.
2Why does the cup help?
It gathers the vibrations and guides them to the ear.
3How is heart rate counted?
By counting beats for a minute.
4Can this tell if someone’s heart is healthy?
No, only a doctor can do that.
Take it further
Try cups of different sizes and tubing lengths and see which gives the loudest sound.
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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