Have you ever wondered why you hear something? OK, probably not. Ever wondered why something sounds the way it does? Possibly, huh? This will explain all of that to you.
You hear sound when something vibrates. These vibrations disturb air currents around the vibrating object, which in turn creates variations in air pressure. "Sound waves" are created from varying air pressures, and these sound waves are transmitted through the air to your ears. They make your eardrum vibrate at a certain frequency, and then you hear the sound that the wave has transmitted. They travel through the air at around 1100 feet per second.
Diagram of a sound wave:
Now that you know just what sound is created from, it's time we delve into the three components of sound: Pitch, Loudness, and Timbre.
Remember those vibrations we talked about earlier? Well, these air patterns are repetitive in nature. This means that they stay at relatively the same "shape" throughout the sound wave. This pattern of a sound is called a "waveshape" or "waveform." The number of repetitions that occur from a specific waveshape is called "frequency." The frequency of a sound is what gives it it's pitch. So, for example, the waveshape of an A "looks" different from the waveshape of a B, and so forth.
A sound with a very high pitch is said to have a high frequency, and a sound with a low pitch has a low frequency. Frequency is measured in "hertz" or "Hz." So when your tuner says "A440," that means that the A note you're tuning to has a frequency of 440 cycles per second.
When a note octaves, it's frequency doubles. So if your tuning pitch is A440, then an octave above that would be A880. And if you wanted to go an octave below A440, it would be A220. Simple, right?
In addition to measuring frequency, we can also measure just how long an actual wave is. This is called "wavelength." The wavelength of a frequency can be calculated by dividing the velocity of sound (1100 fps) by the frequency. So if we wanted to find the wavelength of A440, this is the equation we would have: 1100/440, which comes out to about 2.5 feet.
The range of frequency for human hearing is from about 20 Hz to 20000 Hz.
The strength of the vibrations in air pressure determines the loudness, or volume of a sound. The greater the air pressure variations, the louder we perceive the sound. This is referred to as the "amplitude" of a sound.
To fully understand this, think of font sizes. Here is a letter A at a certain font:
And here is a letter A at a larger font:
It's still the letter A, but one is just bigger than the other.
When I play a note on my guitar, the waveshape will be a certain size. Now, if I play that same exact note, but alot louder, I'll get the same waveshape, but it will just look bigger. It has the same shape, but the proportions are just a bit larger. That's why a note doesn't change it's pitch the louder or softer we strike it.
Sound volume is measured in Decibels (dB). The "threshold of hearing" to "threshold of pain" range is from 0 dB to 120 dB.
Decibel relation chart:
Timbre (pronounced TAM-ber) is what lets us distinguish a guitar sound from a piano sound. Timbre means "tone colour" and different timbres occur because most sounds perceived as pitch actually contain many frequencies other than the fundamental. (The fundamental being the main tone we hear.)
So when someone hears the note "middle C" on a piano, many frequencies besides the C frequency are audible. The other frequencies present occur in a series called the "harmonic" or "overtone" series. The frequency of each harmonic is a whole number multiple of the fundamental frequency. (i.e., 2X, 3X, etc.)
The harmonics of the note A:
So, the second harmonic (the fundamental being considered "one") is and octave above the fundamental, the third harmonic is an octave plus a fifth, and the fourth harmonic is two octaves above the fundamental.
The number of harmonics audible determines the timbre of the sound. Most sounds have timbers that change over time. For example, a low note struck heavily on a guitar will sound bright at first, but as the sound decays, it will become "duller." This shows that the higher harmonics die out quicker than the low ones.
So, in conclusion, while each of the three components of sound are independant of each other, they work together to give each type of sound we hear it's own unique properties.
Think about the complexity of sound the next time you pick up your guitar. Maybe you'll appreciate the science and mathematics behind music a little more.