Step 1: Find out the difference between two noise levels and then find the corresponding row in the left-hand column. You can use this quick reference table to add noise levels together: Difference between two noise levelsĪmount to add to the higher of the two noise levels (dB or dB(A)) For instance, in a factory, if one machine’s noise level is measured at 90 dB(A) and then we start up a second machine also measuring 90 dB(A), the resulting noise is not 180 dB(A), instead, because we know that 3dB represents a doubling of the noise, 90dB + 90dB = 93dB. A Porsche 911 Carrera RSR Turbo 2.1 – 138 dB (see YouTube video of Porsche car noise tests using the Pulsar Nova Sound Level Meter)īecause sound pressure levels in decibels (dB) use a logarithmic scale we can’t just add two dB readings together.How loud are some common sounds in decibel measurements?

The table below summarises this: The basic rules for working with decibels Change in dB The use of the dB unit makes it easier to measure decibels and monitor sound changes if we use these rules. In a work context, this means that a small increase in the number of decibels results in a huge change in the amount of noise and, as such, the potential damage to a person’s hearing. In other words: every increase of 3 dB represents a doubling of sound intensity or acoustic power. When this sound is doubled this equates to a rise of 3dB (decibels), using a logarithmic scale. It can, however, distinguish the significant multiplying of the energy of the sound.

Doubling of sound energyĪlthough the ear can distinguish the rise in level between one or two pins dropping, it cannot distinguish between 10,000,000,000,000 pins and 10,000,000,000,001 pins or even 10,100,000,000,000 because it is not a linear device. A sound 1,000 times more powerful than near total silence is 30 dB, 40 dB and so on. A sound 100 times more powerful than near total silence is 20 dB. On the decibel scale, the quietest audible sound (perceived near total silence) is 0 dB. It is based on orders of magnitude, rather than a standard linear scale, so each mark on the decibel scale is the previous mark multiplied by a value. Sound energy is decreased by a factor of 100ĭid you know: A logarithmic scale is used when there is a large range of quantities.

Sound energy is increased by a factor of 100 Sound energy is decreased by a factor of 10 Sound energy is increased by a factor of 10 It can hear the sound of a pin dropping close-by as well as the roar of a jet engine far away.Īlthough the ear can distinguish the rise in level between one or two pins dropping, it cannot distinguish between 10,000,000,000,000 pins and 10,000,000,000,001 pins or even 10,100,000,000,000 because it is not a linear device. It has a clever in-built mechanism that reduces its own sensitivity as the sound level rises and it also has the remarkable ability to handle an enormous range of sound power levels. The human ear is an extremely versatile and amazing hearing device. It would be tricky to keep an eye on those 14 digits varying in front of you! So, to express levels of sound meaningfully in numbers that are more manageable, a logarithmic scale is used, using 10 as the base, rather than a linear one. If you think about it, it would be very difficult to manufacture a sound level meter that had a linear performance, especially bearing in the mind the range of noise sources to be measured in a work environment. A sound meter uses a display with a decibel range and resolution to approximate the ear’s dynamic range, usually the upper range rather than the quiet part. When you measure noise levels with a sound level meter, you measure the intensity of noise called decibel units (dB).

The decibel scale