The decibel is the unit of measurement, one tenth of a Bel (B), used to measure sound intensity. The decibel is logarithmic in scale and thus represents a ratio.
Sound is quite complex and consists of vibrations traveling through a medium, such as air. These vibrations can be sensed by the human ear as sound pressure. 0 dB is used to represent the threshold of human hearing capabilities and is barely audible under extremely quiet conditions. 120 dB is the threshold for discomfort and 140 dB is the threshold for pain. The most common range, however, is anywhere between 30 dB and 100 dB.
Decibels being logarithmic can not simply be added nor subtracted like other linear units. For example, if you took two sound sources that were measured to be 100 dB and operate them simultaneously, the resulting sound level produced would be 103 dB not 200 dB. If you took four of those same 100 dB sound sources and added them together the resulting sound level would simply be 106 dB, and so on. Due to the logarithmic nature of decibels taking one much louder sound source and adding a substantially quieter one on top of it would not move the measurement in most cases, for example an 80 dB sound source coupled with a 100 dB sound source would still measure 100 dB due to how much louder the 100 dB sound source is.
Some common rules of thumb to consider are that most people perceive 6 to 10 dB in sound pressure level to be a doubling of loudness and can not perceive a change in loudness for anything below a change of 3 dB SPL. Another important thing to consider is how far is the listener from the noise source? A gunshot, no matter how loud, 100 miles away will be unnoticeable regardless of the fact that the gunshot itself is quite loud. This brings us to the difference between sound power level and sound pressure level. Sound power level is the actual acoustical energy emitted by a noise source wheras sound pressure level is how loud that noise source is at a given distance.
Under normal atmospheric conditions the maximum sustained sound level achievable on earth is 194 decibels. The reason for this is that the oscillation of the sound wave can not drop below a vacuum created by the sound pressure in air. However, peak sound levels can achieve levels substantially higher than 194 decibels. One incredible example of this would be the volcanic eruption in Tambora, Indonesia in 1815 which ejected 36 cubic miles, equivalent to a 14 gigaton nuclear bomb based on ejected volume. The internal pressure is believed to have been 47 million pounds per square inch resulting in a measured peak decibel level of 347 dB.
Click here for a chart of typical noise values.
How loud is 0 decibels?
0 decibels, being the threshold of human hearing in a laboratory setting, is quite quiet. This might be comparable to the dropping of a pin in on carpet. In most any case a normal human being would not even detect the noise source. Bear in mind sounds can measure in the negative decibels as well, 0 is not the threshold for sound altogether but simply the threshold for which human hearing begins detecting noises.
How loud is 10 decibels?
An example of a sound source that is 10 decibels is a leaf falling from a tree.
How loud is 15 decibels?
An example of a sound source that is 15 decibels is a cat purring.
How loud is 20 decibels?
A quiet natural area with no wind is typically around 20 decibels.
How loud is 30 decibels?
A typical human whisper is 30 decibels.
How loud is 40 decibels?
A quiet classroom or a suburban area at night can be measured around 40 decibels.
How loud is 50 decibels?
A refrigerator working or a car driving past would be 50 decibels.
How loud is 55 decibels?
An example of 55 decibels is a percolating coffee machine or a household refrigerator.
How loud is 60 decibels?
The sound of a typical human voice or a typical business office ambience would measure to be 60 decibels.
How loud is 65 decibels?
A normal conversation is 65 decibels.
How loud is 70 decibels?
An example of 70 decibels is a household television set on loud or several people on the telephone.
How loud is 75 decibels?
A typical vacuum cleaner or a busy restaurant at lunchtime are examples of 75 decibels.
How loud is 80 decibels?
An alarm clock, freight traffic, a doorbell, and a telephone dial tone are all examples of 80 decibels.
How loud is 85 decibels?
Two good examples of 85 decibels are sawing and typical city traffic.
How loud is 90 decibels?
A truck close by or a human screaming would measure to be 90 decibels. Sustained exposure here can result in hearing loss.
How loud is 95 decibels?
Examples of 95 decibels are a drill or a violin being played.
How loud is 100 decibels?
A machine in a factory, a compressor, and a fighter jet at 300m are examples of 100 decibels.
How loud is 105 decibels?
A helicopter at 100 feet would measure in at 105 decibels.
How loud is 110 decibels?
Two examples of 110 decibels are a typical rock concert or a chainsaw at 3 feet.
How loud is 115 decibels?
The human body begins to perceive vibrations from low frequencies.
How loud is 120 decibels?
120 decibels is the limit of the human voice or how loud a police siren is. 120 decibels is the lowest cited value for the human pain threshold.
How loud is 125 decibels?
A drum set creates a peak noise level of 125 decibels at the moment of striking. At 127 decibels tinnitus can set in from exposure. At 128 decibels the human head begins to detect vibration.
How loud is 130 decibels?
Thunder is roughly 130 decibels in close proximity to the ground strike. At 132 decibels a human can begin to feel their eardrum flex.
How loud is 140 decibels?
A jet engine at 100 feet would measure to be 140 decibels. 140 decibels is the human pain threshold according to OSHA. At 140 decibels the human vocal cord begins to vibrate. At 141 decibels nausea begins to set in.
How loud is 150 decibels?
Fireworks overhead are typically 150 decibels. A sustained noise level of 150 decibels will blur human vision and vibrate human lungs.
An avalanche is typically 170 decibels. At 172 decibels fog can begin to form depending on temperature, humidity, and dew point.
How loud is 180 decibels?
Rocket launch platforms measure in at 180 decibels.
How loud is 194 decibels?
Some larger rockets have measured noise levels of 194 decibels. Between 190 and 195 decibels 50% of human eardrums will rupture. 194 decibels is the loudest possible sustained volume.
How loud is 204 decibels?
The behemoth Saturn V rocket was measured at 204 decibels! Some sources even cite a 220 decibel peak Wow!
Saturn V Rocket Sound Waves
Here you can actually visualize the sound waves from a Saturn V rocket! The Saturn V itself is so loud that it could destroy itself from its own noise levels. NASA has developed a Sound Suppression System that dumps enormous quantities of water continuously onto the launch pad to muffle the sound waves reflecting off the launch pad.