Acoustic telegraph

HOW

1. Two people are needed to perform this experiment.
2. Stand by the two ends of the instrument and try to talk to each other through the device. As one person speaks into the funnel tip, the other person listens by putting their ear to the receiver tip. Try to whisper.
3. Then try to talk directly (without using the telegraph) while remaining in your seats.

WHY

In an unlimited space, the sound wave propagates in all directions and its intensity decreases rapidly with distance. The tube is an enclosed space – a waveguide that directs the sound wave to the receiver, i.e., the ear.