Decibel Scale

Decibel Scale

When looking at the most versatile and amazingly sound devices, nothing can compare to the human ear. With its ingenious internal mechanisms and physiology, the human ear can adjust its sensitivity to increasing sound levels and handle a vast array of sound power levels.

In short, this astounding piece of natural machinery can detect the sound of a nearby pin hitting the floor, and can also shield itself against the roar of an engine not very far away.

While certain sounds may help protect us, others may prove to be damaging.

To help measure the different levels of sound and deem which ones are safe and harmful, experts use a nonlinear scale to describe the intensity of sound waves conveniently. This scale is known as the decibel scale and uses units called decibels (dB).

Simply put, the greater the decibel level, the louder the sound.

Source: Echo Barrier

What are Decibels (dB)?

The decibel’s scientific definition has its roots in the early 20th century and is based on the measurement of power used in telephony back then in the US Bell System; the decibel was initially used to quantify power losses during the transmission of telegraph and telephone signals sent via long cables.

The definition of a decibel is:

“A (UOM – unit of measure) used to show the proportion of one estimation of intensity or field amount to another on a logarithmic scale, the logarithmic amount being known as the force level or field level, individually.”

In simple terms, the decibel is a logarithmic ratio between two values – a measured and a reference value. On a decibel scale, one decibel equals one-tenth (deci-) of one bel, the latter concerning Alexander Graham Bell.

How Does the Decibel Scale Work?

The lowest (quietest) sound on a decibel scale, which is considered near-complete silence, is 0 dB. Regarding the units of 10 as mentioned above, a sound 10 times greater in intensity will be measured as 10 dB; a sound 100 times more intense than 0 dB will be measured as 20 dB; a sound 1,000 times greater in intensity than near silence will be measured as 30 dB, and so on.

Thus, the human perception of sound intensity more closely estimates the logarithm of intensity, instead of assuming a linear relationship. This makes the decibel scale an extremely useful and practical measuring scale for sound.

To better understand how to measure sound, here are the basic rules of how to work with a decibel scale:

Change in dB Change in Sound Intensity/Energy
An increase of 3 dB doubled
A decrease of 3 dB halved
An increase of 10 dB Increased by a factor of 10
A decrease of 10 dB Decreased by a factor of 10
An increase of 20 dB Increased by a factor of 100
A decrease of 20 dB Decreased by a factor of 100


If you have to raise your voice to be heard by another person, you’re probably listening to more than 85 dB sounds.

A sound greater than 85 dB can result in hearing loss, the latter related to both the intensity of the sound and the period of exposure to it; eight hours of exposure to sounds measuring 90 dB can damage the human ear, and exposure to 140 dB can result in immediate damage and cause genuine pain as well.

Some common sounds and their intensity in decibels are as follows:

  • Near complete silence: 0 dB
  • Normal conversation: 60 dB
  • Whisper: 15 dB
  • Library: 45 dB
  • Heavy city traffic: 85 dB
  • Baby crying: 110 dB
  • MP3 player at maximum volume: 105 dB
  • Toilet flushing: 75-85 dB
  • Balloon popping: 157 dB
  • Noisy restaurant: 90 dB
  • Concerts: 120 dB
  • Jet engine: 120 dB


What is measured with the Decibel Scale?

Decibels are widely used to ascertain how loud a sound is since this information is vital to safeguard against ear damage and prevent noise pollution. Whether assessing how much noise building a new road will produce or determining the intensity of music in a theatre, decibels and decibel scale are important measurement tools.

Here are some common areas which utilize the decibel scale to determine the intensity of sound.


The decibel scale is routinely utilized in acoustics to measure the pressure level of sound. The reference pressure level for sound in air is fixed at the usual threshold of sensitivity of the average human.


The decibel scale is mostly used in electronics to express amplitude or power in preference to percentages or arithmetic ratios. The decibel scale is a useful measure since the overall decibel gain from a series of components (amplifiers and attenuators) can simply be determined by summing all individual components’ gains.


In telecommunications, decibels indicate signal losses or gains when sound travels from a transmitter to a receiver via some medium, such as free space, fiber optics, or a coaxial cable.

Video and Digital Imaging

About digital and video image sensors, decibels are generally used to represent ratios of digitized light strengths of video voltages.

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