Final answer:
When shouting across a lake, the phenomenon where your friend hears more than just the original sound is called superposition of sound waves. This effect leads to constructive and destructive interference, which can alter the amplitude and intensity of the resultant sound wave. An echo is a common example of this effect outdoors.
Step-by-step explanation:
When you shout across a lake at your friend, the friend hears more than your sound alone due to the superposition of sound waves. When sound waves overlap, they interfere with each other, creating varying loudness levels at different locations. This phenomenon, known as superposition, occurs because sound from different sources, like a stereo’s speakers or your voice echoing off a surface, can add together in patterns of constructive and destructive interference. This can lead to the sound being amplified or diminished, depending on the relative phase of the waves as they meet.
An example of this effect is an echo, which occurs when sound waves bounce off a large reflecting surface such as a mountain cliff or the surface of a lake. Similarly, when a car passes by with its stereo on, the sound waves emanating from its speakers may overlap with other sounds in the environment, thereby increasing or decreasing the resultant sound's amplitude and intensity.
Moreover, if the source of the sound exceeds the speed of sound, it can result in a shock wave, which is another fascinating effect of superposition. Superposition is a very useful property of waves, it underlines many acoustic phenomena we experience in daily life.