Sound and Wavelengths

I never realized that playing an instrument could have so much to do with physics before.  While playing the piano, fingers hit different notes producing different sounds.  When my sister presses a key on the piano, a pedal connected to the key pounds a string in the back, creating sound waves.  The sound waves are produced by compression and decompression in the air.  The region of compressed air is called a condensation and the region of decompressed air is a rarefaction.  The distance between two maximum condensations or two minimum rarefactions is called a wavelength.  If she strikes a low note, the sound waves produced have longer wavelengths.  If she hits a high note, the sound waves produced have shorter wavelengths.  When a sound wave reaches our ear, the wave causes the eardrum to vibrate.  We technically don't "hear" anything, but we pick up vibrations that our brain interprets into sounds.