Decibel (dB)

by | Apr 10, 2024 | Glossary | 0 comments

Introduction the the Decibel: Understanding Sound Measurement

In the world of sound and acoustics, the decibel (dB) stands as a fundamental unit of measurement, serving as a yardstick for quantifying the intensity of sound. Whether it’s the whisper of a breeze or the roar of a jet engine, the decibel provides a standardised means to express the power and loudness of sound waves.

The History of the Decibel

Named after Alexander Graham Bell, the inventor of the telephone, the decibel scale offers a logarithmic representation of sound levels. This logarithmic nature is not intuitive at first glance but holds profound significance in accurately portraying the human perception of sound intensity. Understanding the decibel scale and its applications is crucial for a diverse range of fields, including engineering, environmental science, medicine, and entertainment.

At its core, the decibel scale allows us to express vast differences in sound levels using manageable numbers. For instance, while the quiet rustle of leaves might register around 20 dB, the thunderous blast of a rocket launch can soar beyond 180 dB. This logarithmic scale compresses this enormous range into a more digestible form, making it easier to compare and analyse various sound intensities.

One of the unique aspects of the decibel scale is its reference point. Unlike many other units of measurement that start from zero, the decibel scale begins from a baseline corresponding to the threshold of human hearing. Specifically, 0 dB represents the faintest sound that the average human ear can detect, known as the auditory threshold. From this starting point, sound levels are measured relative to this baseline, with positive values denoting increasing loudness and negative values indicating decreasing sound intensity.

Moreover, the decibel scale is not linear but logarithmic, meaning that each increase of 10 dB represents a tenfold increase in sound intensity. For example, a sound measured at 70 dB is not twice as loud as one measured at 60 dB; rather, it’s ten times louder. This logarithmic nature reflects the nonlinear way in which our ears perceive sound, aligning more closely with our subjective experience of loudness.

The Application of the Decibel

In practical terms, the decibel scale finds widespread use in various applications, from assessing noise pollution and ensuring workplace safety to designing concert venues and optimizing audio systems. By providing a standardized framework for quantifying sound levels, the decibel empowers researchers, engineers, and policymakers to tackle noise-related challenges effectively and promote environments conducive to human well-being.

In the subsequent sections, we will explore the significance of decibel levels in different contexts, ranging from everyday environments like homes and offices to specialized settings such as industrial zones and entertainment venues. Through this exploration, we aim to deepen our understanding of the decibel and its profound implications for our auditory experience and quality of life.

Typical Noise Levels, dB(A)

Noise Level, dB(A)Example
130Threshold of pain
120Jet aircraft take-off at 100m
110Chain saw at 1m
100Inside disco
90Heavy lorries at 5m
80Kerbside of busy street
70Loud radio (in typical domestic room)
60Office or restaurant
50Domestic fan heater at 1m
40Living room
20Remote countryside on still night

We Mentioned dB(A), So What Does That Mean?

The unit used to define a weighted sound pressure level, which correlates well with the subjective response to sound. The ‘A’ weighting follows the frequency response of the human ear, which is less sensitive to low and very high frequencies than it is to those in the range 500Hz to 4kHz.

In some statistical descriptors the ‘A’ weighting forms part of a subscript, such as LA10, LA90, and LAeq for the ‘A’ weighted equivalent continuous noise level.


The decibel (dB) scale serves as a fundamental unit for quantifying sound intensity, offering a logarithmic representation of sound levels. Starting from the threshold of human hearing at 0 dB, the scale reflects both increases and decreases in sound intensity relative to this baseline. Each 10 dB increase signifies a tenfold rise in sound intensity. Understanding decibel levels is crucial for diverse fields such as building compliance, environmental standards, and occupational safety. This logarithmic scale aligns with human perception of sound, enabling effective management of noise pollution and creation of conducive environments across residential, commercial, and industrial settings