9.04 Sound Waves

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Properties of Sound Energy

The properties of sound are:

• Intensity
• Loudness

Intensity is the amount of energy that passes through a certain area in a specific amount of time. The higher the sound volume is turned up the farther the sound wave will travel. Sound intensity is measured in decibels (dB).

Image courtesy of US Occupational Safety and Health Administration, Figure 3.0 Decibel Scale.

Why does sound seem to decrease with distance? As sound waves travel, the energy they carry spreads out. This decreases the distance the waves can travel. Also, some of the sound waves energy converts to other forms of energy (mostly thermal) as the sound travels through matter.

Image courtesy of US Occupational Safety and Health Administration, Figure 4. Sound Pressure Levels in a Free Field

Loudness is the perception of sound volume and primarily depends on the intensity. The higher the intensity the louder the sound. Listening to loud music or hearing loud noises, especially close to the ear can cause hearing damage. A ringing in the ear after hearing loud noises or listening to loud music is an indication of hearing damage.