1. Intensity Waves and Sound

2. Sound Waves
Pitch: Frequency. In music frequency corresponds to the notes the musical notes.
Loudness: Amplitude. When you adjust the volume on an stereo amplifier, you are adjusting the amplitude of the sound waves. The amplitude is the the size of the waves measured from equilibrium. Changing the amplitude does not change the wavelength. As a result, the frequency remains constant and the notes you hear are the same. They are just louder or quieter.
Range of human hearing: 20 Hz to 20,000 Hz. Living in the noise filled modern world destroys the ability to hear over time. Most people cannot hear this entire range. One of the most damaging modern devices is ear buds. The noise is delivered so directly to the ear drum that it can cause severe damage in a short amount of time.
Ultrasound: Sound above 20,000 Hz (above the range of human hearing)
Infrasound: Sound below 20 Hz (below the range of human hearing)

3. Waves Transmit Energy
Energy: The energy of a wave is related to its frequency and amplitude.
Waves with higher frequency have greater energy.
Waves with greater amplitude have higher energy.
Power: The rate that waves transmit energy.
Intensity: The ratio of power and area.
Sound spreads spherically, and the surface area of a sphere is: A = 4πr2
This means that intensity follows the inverse square law. As distance increases the intensity of sound is reduced by the inverse square of distance.