SOUND PRESSURE LEVEL

Key points:

• The ear is the most sensitive human organ. Vibrations on the order of angstroms are used to transduce sound. It has the largest dynamic range (~140 dB) of any organ in the human body.
  
  
• The lower portion of the curve is an audiogram - hearing sensitivity. It can vary up to 20 dB across listeners.
  
  
• Above 120 dB corresponds to your favorite heavy metal rock and roll band (or standing under a Boeing 747 when it takes off).
  
  
• Typical ambient office noise is about 55 dB.
  
  
• Three common weighting scales exist for intensity - A (SPL in the range 20 to 55 dB), B (SPL in the range 55 to 85 dB), and C (85 dB or more). A weighting is used most often in speech research (and by the government when setting regulations).