Decibels (dB) is a unit for sound intensity.  For each increase of 10 decibels, the sound level perceived by our ears doubles.  So, 100 decibels is actually twice as loud as 90 decibels, and this is why in the upper volume levels hearing damage can occur so quickly.  Decibel level is a logarithmic scale.  You would not notice a decibel change of 1 dB.  You would barely notice a change of 3 dB, but a change of 5 dB, would be clearly noticeable.  A change of 10 dB would be about twice as loud and a change of 20 dB would be a sound four times as loud.  Look at the noice level chart to see the dB level or common sounds. 

It is important to watch the dB levels that you hear everyday.  Exposure to loud sounds, in the form of noise or music, has been shown to cause the ear to lose its sensitivity, especially to high frequencies.  The longer a person is exposed to loud sounds, the greater the effect.  A person can recover from short term exposure in a period of hours, but the effects of long term exposure can last for days or weeks.  Long exposure to 100 dB or greater sound levels can produce permanent damage.

There is a limit to how much sound we can hear in a day without causing damage to our hearing.  Hearing loss can result from loud music being transmitted through headphones.  Cotton earplugs reduce the sound level only by about 10 dB.  Special ear inserts can provide a 25 dB reduction.  Specifically designed earmuffs and inserts as you can see workers using in an airport can reduce the sound level by up to 45 dB. 

Sound waves cause vibrations in the eardrum.  Most people cannot hear sounds less than 20 Hz and greater than 16,000 Hz.  Normally, people are sensitive to sounds in the 1,000 Hz - 5,000 Hz range.

Humans naturally lose their hearing as they age.  By listening to loud sounds over 85 dB, that hearing loss can be accelerated.  The chart shows OSHA's permissible noise exposure limits.  The exposure limit is how long you can listen to sounds at that level per day before having long term damage to your hearing.  That doesn't mean that you can listen to 90 dB for 8 hours and then 92 dB for 6 hours.  The exposure limit is the total amount of sound level that you can listen to that day.  Hearing loss in teenagers is becoming a real medical issue.  Click here to read an article about teenagers and hearing loss.  It is important to monitor how loud the sound you are listening to is.

Loudness depends on the amplitude of the pressure variation wave.  The more amplitude you have, the louder the sound.

What is the loudest possible sound? What about the quietest thing we can hear? What do decibels measure, anyway? In this video you'll learn what makes sound and explains the issues of loud sounds.