Sound and Hearing

What is Sound?

What is sound and what does it look like?

Sound is a vibration. When one object strikes another, a vibration is created. A good example is when a hand or drumstick strikes a drum, causing it to vibrate. The vibration moves the surrounding air molecules away from the drum. As these molecules move, they travel outwards in all directions. This vibration is called a sound wave.

Here is what a sound wave looks like:

A famous deaf percussionist, Evelyn Glennie, described sound as "a specialized form of touch". She is right because when vibrated, one molecule touches the next, and so on. Sound can be a rhythmic movement of molecules. When many types of sound are put together, they form music, or speech, or noise. The possibilities are endless!

Sound can travel through solids, such as metal, through liquids, such as water, and finally through gas (usually air!). Our ears work best with sound travelling through air, so we will look at this mode of transmission more closely. Here is an example of one object striking another to make sound. In this case, the object is sound, and it is striking a speaker. The speaker vibrates and transmits the sound into the air:

To talk about the properties of sound, it is helpful to use a model. The model most often used to describe sound is a sine wave.

Here is a simple sine wave:

Sine Wav

Click above image for Large View.

Amplitude is the scientific term for loudness. The louder the sound, the more energy it has and the larger its amplitude will be. Softer sounds have less energy and smaller amplitude. These sine waves show you the differences between small and large amplitude:

Sine Wav

Click above image for Large View.

The reason your stereo has an 'amplifier' is to make the sound louder. When you turn up the volume, you are amplifying the sound. This louder sound has more energy. This energy will vibrate your speakers like this:

If you turn your volume up loud enough you can blow out your speakers because the energy is so great it will literally rip the speaker diaphragm apart. Then the sound coming through the speaker will be distorted.


When musicians talk about a 'high' or 'low' sound, they are referring to 'pitch'. The scientific term for pitch is frequency. When a sound wave repeats more frequently, or has more cycles per second, it changes to a higher pitch. When the sound wave repeats less frequently, or has fewer cycles per second, it changes to a lower pitch.

Sine Wav

Click above image for Large View.

An example of a high frequency sound is a singer singing the note of high C. An example of a low frequency sound is that same singer singing the note of low G on the musical scale.


Music, voices, noise, how does all of this sound get into our heads? It is carried from the world around you into your head via your ears. Our amazing ears catch, channel, and interpret everything we hear, 24/7. They never shut off. Below is a preview of how sound travels through your ears to your brain:

Back to Sound and Hearing »

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