Available operators:+ - |

Enter in the calculator 80-75 and press calculate. The result is 78.3dBA

This means the sound source produces 78.3dBA at the point of measurement without background noise.

38 + 40 + 29= 42.3dBA

result=10*Log(10

This calculator uses the Inverse Square Law which allows you to estimate the sound reduction over distance.
It can be applied in situations where the sound can propagate freely and
is not confined by walls or other large objects.
The sound level drops by 6dB when you double the distance to the sound source.
10 times the distance drops the sound level by 20dB.
Enter 3 values and the calculator will calculate the 4th value for you.
L = sound level in db or dBA, d = distance in m (meter) or ft (feet). Do not mix units. Use either ft or m. |

Example: L1=80dBA at d1=1.5m, What is the sound level at d2=4.5m?

Enter the values 80 (L1), 1.5 (d1) and 4.5 (d2) into the calculator and it will calculate L2=70.5dBA.

Do not get too close to the source when you measure L1 but be close enough such that background noise is neglectable. Common good values are 1.5meter or 2meter for d1.

Example: L2=50dBA at d2=100m, What is the sound level at d1=1.5m?

Enter the values 50 (L2), 100 (d2) and 1.5 (d1) into the calculator and it will calculate L1=86.5dBA.

ΔL=10*Log(i2/i1)

where ΔL is the difference in sound levels (L1-L2) in dB (or dBA).

The quotient i2/i1 is the sound intensity ratio.

This formula works as long as you have spherical wavefronts. Some sound sources such as e.g a large fan may produce parallel wavefronts directly at the fan and they become spherical only as you go further away. d1 must therefore not be too small. Common good values for d1 are 1m (3ft) to 2m (6ft) dependent on the size of the sound emitting object.

The weakest audible sound is 0 dB and a quiet conversation is 100000 times more intense or 50 dB higher.

Explanations:

Sound intensity: Intensity is the amount of energy transmitted per second over an area. It is measured in watt/m

Sound pressure: Sound pressure is what microphones measure in the form of the amplitude. It is proportional to the square root of intensity (P=sqrt(I) or I = P

Pressure ratio = 10

- Noise:

Noise is unwanted sound which may be hazardous to health, interfere with speech and verbal communications or is otherwise disturbing, irritating or annoying. - Sound:

Sound is as any pressure variation in a gas or liquid that can be detected by the human ear. - Wavelength:

wavelength = velocity/frequency

The velocity or speed of sound in air is**340m/s**. - dB vs dBA:

Humans do not hear all frequencies equally. To account for this, different weightings have been created. "A" weighted sound levels are referred to dBA. See https://en.wikipedia.org/wiki/A-weighting.

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© Guido Socher, version 2023-10-07

You can install this calculator on your PC simply by saving this web page on your desktop. (Firefox->right click->Save Page As)

History: 2017-07-05 - first version, 2018-05-20 - cleanup code for better compatibilty, 2019-08-07 - typo corrected, 2023-10-07 - add formula for ratio