Tin can telephones

Foundation of Communication > Tin can telephones

Sound Waves are Longitudinal Waves that consist of a series of Compressions followed by Rarefactions, they propagate through Media such as air, water or solids. Sound Waves propagate much better and faster in solid material than in air.

When someone speaks or makes a sound, the air ripples or vibrates. Our ears collect the sound vibration, or sound waves and send them to our brains. Then we hear the sound.

When you pull the string tight and talk into one of the cans of the tin can telephone, the sound vibrates across the taut string to the other can. The person at the other end of the telephone hears your message after his or her ears collect the sound vibrations and send them to the brain to be processed.

The physical characteristics of sound are Frequency, Wavelength, Amplitude and Velocity.

Frequency and Wavelength: The frequency f is the number of waves that pass through a point in a second, measured in Hertz. The wavelength λ is the distance between two successive wave crests. The frequency and wavelength are related to the Velocity of sound v by the equation:

λ x f = v

The Amplitude is the difference between the maximum and minimum pressures within the waves.

The Velocity depends on the medium and its temperature and pressure. In dry air at 20°C the speed of sound is approximately 343 m/s. The speed is faster in denser or solid materials, such as water, steel or a taut string.

Foundation of Communication > Tin can telephones