Pitch and volume are two different properties of sound. Pitch is how high or low a sound is — a whistle has a high pitch and a drum has a low pitch. Pitch depends on how fast something vibrates: faster vibrations make higher sounds. Volume is how loud or soft a sound is. Volume depends on how big the vibrations are: bigger vibrations make louder sounds. You can change pitch and volume independently.
Fill glasses with different amounts of water and tap them to hear different pitches. Pluck a rubber band gently (soft) and hard (loud) to hear volume change. Use a ruler hanging off a desk edge — change the overhang length to change pitch, and pluck harder or softer to change volume.
When you listen to music, you hear some notes that are high, like a flute, and some that are low, like a bass drum. That difference is called pitch. Pitch is determined by how fast something vibrates. Scientists call the speed of vibration frequency. An object vibrating 440 times per second produces the musical note A, which is the note orchestras tune to. Vibrate faster, and the pitch goes up. Vibrate slower, and it goes down.
You can change pitch in several ways. A short guitar string vibrates faster than a long one, so it produces a higher pitch. A tight rubber band vibrates faster than a loose one. A small bell vibrates faster than a big one. In every case, the thing that changes pitch is the speed of the vibration. Think of a ruler sticking off the edge of a desk — push the short end down and let it go. A short overhang vibrates quickly and sounds high-pitched. A long overhang vibrates slowly and sounds low-pitched.
Volume is completely different from pitch. Volume is how loud or soft a sound is, and it depends on the size of the vibrations, called amplitude. Hit a drum gently, and the drum skin vibrates a small amount — quiet sound. Hit the drum hard, and the skin vibrates a big amount — loud sound. Both hits can have the same pitch because the speed of vibration has not changed, only the size.
Volume also changes with distance. Sound waves spread out as they travel, so the farther you are from the source, the quieter it sounds. This is why someone shouting from far away sounds quieter than someone whispering right next to you. Pitch and volume together describe most of what you notice about any sound — whether it is the high, soft chirp of a bird or the low, booming rumble of thunder. They are the two independent knobs that nature uses to create the incredible variety of sounds in the world.