26: Pitch & Frequency
Lesson 26: Pitch & FrequencyThis lesson is for those who want to know more about how pitch works, "physically", beyond our brief "musical" description in Lesson 2: Pitch & Keyboard.
First, a brief definition of sound: Sound is what happens when an object vibrates or "shakes"; the shaking object makes the air shake; and the shaking air makes your ear shake. Note that these "sound shakes" are too weak, and too fast, for your body to feel them, which is why we have ears that can feel them, as sound.
However, not all sounds have pitch. When the air shakes back and forth ("vibrates"), over and over, at a constant speed, long enough for your ear to "measure" the speed, that's when you hear a pitch. Slow vibrations make "low" pitches; fast vibrations make "high" pitches.
A pitch is measured by its frequency, which just means its "speed" in vibrations per second. Vibrations-per-second is also called Hertz; the abbreviation for Hertz is Hz. For example, the pitch "A above middle C" has a frequency of 440 Hz; that means that it's vibrating back and forth 440 times in a second.
If you understand pitches and their frequencies, then you can go on and learn how a single musical tone contains multiple frequencies, in Harmonics.