Decibels – why we use them and what they mean

Decibels – why we use them and what they mean

The way we hear and interpret sound is very complex, and with a hearing range so wide, a system needed to be introduced which would allow the representation of sound on a smaller scale than a normal linear method. Decibels – why we use them and what they mean?

Similar to the Richter scale for earthquakes, and now, the unfortunately very familiar, R rate for virus reproduction, sound is measured using a logarithmic scale and is measured in Decibels.

While mathematically quite compacted, logarithmic scales allow us to represent large ranges of numbers easily. Audible sounds have a power range from 10-12 Wm-2 to more than 100Wm-2 – this is a range of more than a million-millions to one. Sound power is important as it plays a big part in the subjective nature of sound and the perception of loudness.

Taking this huge range of numbers and turning it into a scale of 0-120dB makes it much easier to understand and use. We will not go in depth about logarithms or any further on the mathematical side, but understanding that the dB scale is logarithmic is fundamental to your understanding of decibels.


At a glance, this list gives rough reference points for how loud something is in dBA*:

140 dBA Threshold of pain

120 dBA Jet aircraft at 100m – the threshold of discomfort

110 dBA Inside a very noisy factory

100 dBA Road drill, loud disco

90 dBA DIY drill (close to ear), lorry (roadside)

80dBA Traffic at a busy road-side

70 dBA Hair dryer

60 dBA Washing machine

50 dBA TV in lounge

40 dBA Quiet office

30 dBA Bedroom at night

10 – 20 dBA Broadcasting studio (background noise level)

0 dBA Threshold of hearing


What is a good dB reduction figure when looking for soundproofing materials?

As we can see from the table above, 10dB difference is a significant change in loudness. When looking at dB ratings for products and systems, it is a consideration to note the following facts:

  • A 10dB increase/decrease is perceived as a doubling/halving of loudness
  • A reduction of 45dB is usually the target for domestic buildings (both for internal structures and party walls etc.)
  • For airborne noise, the target dB reduction will be as high as possible and for impact noise it will be as low as possible
  • You can measure the dB level for noise at its loudest and then deduct normal background noise from this figure to ascertain target sound reduction figures
  • Different soundproofing systems offer different dB ratings, the highest rated system may not be most suitable for your situation


Here at ClearSound Acoustics we have the expertise and experience to help guide you to the right products. Contact us for help dealing with noisy neighbours, local factory noise, creating a home office or any other soundproofing and interior acoustics needs.


For further information about building regulations in the UK, please visit the site here

Our soundproofing range is perfect for protection against noisy neighbours, visit our domestic soundproofing section.

*the dBA in this chart is shown as it using ‘A’ weighted figures. This means that the dB ratings are given difference levels of significance across difference frequencies based on human hearing response which gives a more accurate reflection of the loudness perceived by the human ear. It is common to use ‘A weighted’ results in this fashion. It can be less useful when dealing with very loud bass frequencies but is a good measure for ‘normal’ noise.

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