Make a homemade hearing aid
Everything that moves makes a sound by causing vibrations or movement of air. If you don’t believe this, next time Dad is kicked back in his easy chair watching TV, sneak up behind him with two metal pots and bang them together real hard. Now listen carefully to the whooshing sound as Dad flies out of his chair and runs at you. By the way, if Dad offers no reaction and instead lies incredibly still, throw some water on him…
The vibration or movement of air is the basis for sound. Our ears collect these air movements and change them to nerve signals that are sent to our brains. Our brain interprets these signals as sound.
What if we could collect more sound waves than usual? Would we have super-human hearing? You bet. In this experiment, we’ll construct a sound collector that will allow us to hear a whisper from across the room. If you conducted the mini-assessment discussed above, you can also use this device to check Dad for a pulse…
- Take a large sheet of paper and roll it into a cone shape. One end should be as large as possible. The smaller end should have a hole about the size of a dime.
- Tape the paper so the cone does not come unraveled.
- Hold the narrow end of the cone to your ear.
We interrupt this experiment for a special safety note: Do NOT stick the narrow end of the cone in your ear (it can damage your ears). We once had a friend named Carl Maloney who once did this. The cone got stuck! Sure, Carl could hear really well after this incident (you couldn’t sneak up on him no matter how hard you tried), but he forever found it rather difficult to pass through narrow doors.
- Now, turn around the room carefully noting the sounds that you hear.
Our homemade hearing aid works by collecting sound waves in the large end of the cone and funneling them through the narrow end of the cone into our ears. Since more sound waves are gathered than would typically be possible, you should find that you can hear quiet sounds much more clearly. You may notice that the shape of our ears naturally works the same way – they gather sound waves for us!
Additional notes about the homemade hearing aid experiment
An ear trumpet is a tubular or funnel-shaped device, often made of sheet metal, silver, wood, snail shells or animal horns. It collects sound waves and leads them into the ear.
The use of ear trumpets for the partially deaf dates back to the 17th century. The earliest description of an ear trumpet was given by the French Jesuit priest and mathematician Jean Leurechon in his work Recreations mathématiques (1634). Polymath Athanasius Kircher also described a similar device in 1650.
Ear trumpets were used as hearing aids, strengthening the sound energy impact on the eardrum and thus improving hearing for a deaf or hard-of-hearing individual.
Note that a sound trumpet does not “amplify” sound. It takes the sound power received over a large area and concentrates it into a smaller area. The received sound is louder, but no power has been created in the process.
There are two different types of hearing aids
There are two types of hearing aids, air-conduction aids, and bone-conduction aids. An air-conduction aid amplifies sound and brings it directly into the ear. Most people who use hearing aids have this type of aid. However, in some people, sound cannot be transmitted through the outer or middle ear. These people often use a bone-conduction aid, which brings sound waves to the bony part of the head behind the ear. The bone transmits vibrations to the auditory nerves of the cochlea. Hearing is possible when these nerves are stimulated.
Experiment supplies for the homemade hearing aid experiment
Supplies: Tape, Paper
In-Article Image CreditsOld hearing aid ear trumpet device via Unknown with usage type - Public Domain
Old hearing aid ear trumpet device via Unknown with usage type - Public Domain
Madame de Meuron using an ear trumpet via Wikimedia Commons with usage type - Public Domain
Featured Image CreditOld hearing aid ear trumpet device via Unknown with usage type - Public Domain