The unit used to measure the intensity of sound is called a decibel (dB). Sounds measuring up to 75 dB are considered to be in the "safe zone". Constant exposure to sound at these levels is very unlikely to cause long-term lasting hearing damage. The sound of a conversation at normal volume measures approximately 60 dB and the sound of a running dishwasher measures approximately 75 dB. Sounds around the 85 dB level are considered a moderate risk to hearing. Exposure to these levels for long periods of time can lead to some form of damage causing NIHL. Sounds at these levels include heavy traffic and crowded areas at 85 dB, active subway stations at 95 dB, and listening to an mp3 player with earphones at maximum volume at 105 dB where listening for just 15 minutes can cause permanent damage. Sound at 120 dB and above is in the "danger zone". This level of sound must be avoided at all costs as exposure to even a brief pulse will lead to immediate permanent damage. This level includes the sound of ambulance sirens at 120 dB, a plane taking off at 140 dB, and gunshots at 165 dB and above. (Rabinowitz,