Can you hear the ocean when you hold a seashell to your ear?

Have you ever tried holding a seashell to your ear to bring back the beach you just left? It seems like no matter how far away the beach is, so long as you have that shell, you can put the seashell up to your ear and hear the roar of the waves rolling on the shore. The best shells for producing this sound are large spiral conch shells.

Some people suggest that the sound you hear in the seashell is the echo of your blood rushing through the blood vessels of your ear. If this were true, then the sound would get louder after exercising, since your blood flows faster after exercising; however, the sound is the same before and after exercise.

Others think that the wave sound inside the shell comes from air flowing through the shell. The air flowing in and out of the shell creates the sound. The sound is louder when you pull the shell away from your ear than when it is right up against your head. This theory does not hold true in a soundproof room. In a soundproof room, there is still air, but when you hold the shell to your ear, you no longer hear the ocean.

The most likely explanation for the wave sound is the background noise from around you. You may not even notice these background noises any other time, but the shape of the shell causes the sounds to be amplified (made louder). The shell “collects” the sounds from your surrounding, so what you hear when you hold the shell up to your ear are all the background noises bouncing back out of the shell.

You don’t even need the seashell to hear the noise. You can produce the same ocean sound using an empty cup or even by cupping your hand over your ear. Go ahead and try it, and vary the distance at which you place the cup near your ear. The level of the sound will vary depending on the angle and distance the cup is from your ear.

Noise from outside the shell can also change the intensity of the sound you hear inside the shell. You can look at the shell as an amplifying chamber. When sound from outside enters the shell, it bounces around, creating an audible noise. So, the louder the environment you are in, the louder the ocean sound will be.