What is dB? A Complete Guide for Measuring Sound using Decibel

You are always surrounded by sound whether you’re at home, at the workplace, or simply walking on the street. From the music you hear through your earbuds to the communication in which you engage daily and the noises from the outside environment, everything produces a unique sound. So, did you ever think of measuring the sound intensity? 

It does appear to be an impossible task, but thanks to some of the renowned measuring units for making it possible. One of the widely utilized units for quantifying sound is decibel (db or dB). It is a basic concept in various fields, including telecommunication, electronics, and acoustics, and plays a vital role in comprehending and administering sound in different applications. 

So, in this article, you will learn what is dB. You will understand what this unit is, how to calculate it, and the different ways it can be applied.

What is dB?

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Decibel Scale Sound Levels illustration

A dB or decibel is a measuring unit that evaluates the relative power or intensity of sound, generally in contrast with a reference point. It is named after the famous Alexander Graham Bell, who is known for inventing the telephone. dB is a logarithmic unit, which means it displays numerical data of different values, confirming that it is not linear but formed on the power of 10. The dB scale is utilized to express an extensive range of values, starting from the dizzy sounds all the way to the blaring noises, but in a standardized and well-organized way. 

What is the dB Scale?

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Decibel Scale Sound Levels illustration

The dB scale is used to show the ratio of two different levels of intensity, such as the sound wave power, as opposed to a reference power. Here is the formula used to calculate this ratio:

10 log (P2 / P1) dB

Calculating dB

To understand how to calculate dB, let’s take a simple example into consideration. For instance, you have two loudspeakers playing two different sounds. The first speaker represents P1, while the second represents P2. However, both speakers have similar elements, such as frequency. So, using a dB unit, the difference between these two will be none since the intensity of sound from both loudspeakers is the same. The results will be similar too.

Note: Remember, the log will always be 10 

However, if the second loudspeaker (P2) produces more power (twice compared to P1), the difference in dB will be:

10 log (P2 / P1) dB 

= 10 log 2 

= 3 dB

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Similarly, if the second loudspeaker is 10 times more powerful than the first loudspeaker, then:

10 log (P2 / P1) dB 

= 10 log 10 

= 10 dB

This means the difference in the sound intensity will be 10 dB.

Another scenario is that if the second speaker is 1 million times stronger than the first one, then:

10 log (P2 / P1) dB 

= 10 log 10,00,000 

= 60 dB

Here, the dissimilarity between sound intensity will be 60 dB.

What are Reference Levels in dB?

To make more sense of decibel calculations, you need to have a reference point. Reference levels are important as they offer a proper context and permit you to comprehend whether a sound is quieter or louder than the reference sound. Moreover, you must understand that the uses of these levels can be different, depending on the implementations and field. So, let’s explore some common reference levels in dB.

a. Power Level

In the field of electronic systems, the power level is 1 mW (milliwatt). This reference is used to measure all the power levels in the circuits of electronic equipment and is denoted by ‘dBm.’

b. Sound Pressure Level (SPL)

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SPL has a reference level of 20 micropascals, and it is the most common level in acoustics. This reference level is the approximate intensity of human hearing at 1000 Hz frequency. Engineers use it to quantify sound pressure levels, and it is usually indicated as ‘dB SPL.’

c. Hearing Level

Digging deeper into discussing the hearing threshold, its reference level is marked as the quietest sound a human ear can listen to. In other words, the hearing threshold reference level defines the lowest level of the sound humans can hear. This is generally described as 0 dB and indicated as “dB HL.’

d. Sound Equipment

In sound engineering, the reference level for power or voltage is often fixed at 0.775 volts RMS. This reference level is termed as 0 dBu.

Common Decibel (dB) Measurements

As you already know, dB is used to calculate various sound features and signal intensity, covering different fields, so here are a few common applications of dB measurements. 

a. Signal-to-Noise Ratio (SNR)

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In signal processing and telecommunications, the SNR is demonstrated in decibels. It calculates the ratio of the intensity of the desired signal to the intensity of the background noise. To understand the signal-to-noise ratio, here’s a simple example. 

Imagine you are listening to a radio station. So, the signals from the station indicate the ‘desired signals,’ and unwanted noises, like interference, indicate the background noise. If the radio signal is powerful and there is minimal interference, you will receive a high SNR. But, if the radio signal is weak with interference, you will experience a low SNR.

b. Sound Pressure Level (SPL)

No, it is not a mistake that you are reading about SPL again under this section; in fact, it discusses this reference in depth. Sound pressure levels help measure sound wave intensity as it spreads in the air. The SPL levels you experience in your daily life may mostly range from an almost-silent whispering at 20 dB SPL to the immensity of pain, which is around 130 dB SPL. 

For example, if you are whispering in your friend’s ear during a college lecture, those sounds will have the highest SPL range of 20 dB and not more than that. Likewise, if someone shouts in pain, the maximum sound pressure level will be 130 dB. 

c. Frequency Response

Audio devices like headphones and speakers sometimes use decibels to label their frequency response in order to represent how they regenerate various frequencies. For instance, a speaker may offer a +/- (both positive and negative) 3 dB ranging from 50Hz to 20kHz. This demonstrates that the signal out will remain with the reference level of 3 dB throughout that range.

d. Sound Exposure Levels

To ensure workplace safety and environmental noise analysis, sound exposure levels (SELs) are utilized to calculate sound intensity in a particular time period. The results are expressed in decibels or ‘dB SEL’ and are utilized to evaluate potential hearing loss.

e. Attenuation and Gain

Decibels are used to measure attenuation (reduced intensity) and gain (increased intensity) of signals in audio systems and electronic circuits. For example, if an amplifier expands the input power of signals by the 10th factor, it will be said as a 10 dB gain. 

Decibel (dB) Uses in Ordinary Routine

Decibels are an important unit of measuring sound power. It plays a key role in various daily scenarios, helping humans enhance their quality of life and well-being. So, let’s read about its contributions on a daily basis in different realms. 

Occupational Safety Standards

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As discussed before, decibels play a great role in workplace safety. It helps set safe noise exposure levels in the working environment. Remember, too much noise can cause hearing and various other health problems. Moreover, according to the National Institute for Occupational Safety and Health (NIOSH), workers must wear hearing protection gear if the work area has noise levels of more than 85 dBA

Therefore, decibel measurements are set to determine noise levels, helping employers assess whether their employees must use hearing protection devices. This ensures that all the workers are safeguarded from the noxious effects of extremely high noise levels, 

Entertainment Industry

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In the world of music and entertainment, dBs are the basic parameter. Audio engineers, musicians, producers, and concert locations rely heavily on decibel calculations to keep a balance between hearing health and high auditory experience. In other words, through decibels, sound engineers can deliver loud audio without hurting the audience’s hearing capabilities. This gives a great advantage to both liver performers and the audience. 

SPL meters are used to monitor the loudness of sound, allowing real-time adjustments to make sure the sound levels stay within safe limits. This use of dBs ensures that music concerts or events are not only enjoyable but also secure for everyone. 

Home Audio Devices

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Last but not least, when it comes to home entertainment systems, decibels are used to attain a perfect balance of sound from amplifiers and speakers. This ensures that you have the best listening experience when watching movies, enjoying music, or any other type of entertainment. 

Controlling Noise Pollution

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Decibels also have an immense effect on controlling and supervising environmental noise, especially when it comes to urban planning. Noise pollution from different mediums, such as industries and transportation, can negatively impact the overall health of the people. So, decibel measurements help create policies to control and mitigate the severity of noise to make sure society remains peaceful and savors a good, healthy life. 

The Contribution of Decibels (dB) in Technical Devices

Not only sound and acoustics but decibels are used in a wide range of engineering and physics fields, such as:

a. Electricity

In terms of electronic power and electricity, decibels are widely utilized to demonstrate current, voltage, and power levels. For instance, to determine how accomplished a particular amplifier is, you can quantify its gain levels, which are described in dB. Likewise, when it comes to radio engineering, the transmitter’s output power is measured in dB, allowing engineers to sketch a clear picture of the radiated power. Moreover, decibels are also used to define voltage levels in all electrical circuits. This makes it simple to assess and design a broad range of electronic systems. 

b. Radio Frequency

Decibel measurements influence radio frequency (RF) and the overall antenna design. Engineers use dB to appraise the loss or gain of antennas. So, by showing these measurements in dBs, they can find out the antenna’s performance accurately. At the same time, decibels are also employed to evaluate power levels and cable signal loss in radio communication, improving wireless networks for high-end signal transmission.

c. Optical Cable

Light power and optics are also measured in dB. The optical power or light intensity is usually described by decibels. This trait is of high value in communication and networking fields, where optical fibers are essential for transferring data at long distances. Through decibel measurements, researchers and engineers can gauge signal strength correctly, which helps them in designing and maintaining optical systems. 

Common Myths about Decibels Explained with Facts

Despite a clear usability, decibels often confuse many people. Some of the most common misconceptions about dB are clarified below.

Myth 1: Decibels Have Absolute Measurement Unit

Decibels do not possess a constant unit of measurement; in fact, they are relative. That is why, to comprehend a decibel value fully, you must know the levels that are being utilized or the reference point. 

Myth 2: Decibels Have Rigid Dimensions

Decibels have no fixed dimensions. In other other words, they are free from a persistent unit. So, when you say ‘5 dB,’ you are not saying it in the context of 5 units of any specific quantity. Instead, you are demonstrating a relative change in the intensity.

Myth 3: Negative Decibel Means No Signal

If a decibel is negative, such as -30 dB, it does not mean it lacks signal, or there is no sound. It is an indication that the power or intensity of sound is lesser than the reference level. 

Myth 4: Decibels have Minimum/Maximum Values

Decibels do not have any minimum or maximum values. They can be both negative and positive, depending on the application and field. For instance, a speaker can have a gain of 30 dB or more, and noise levels can be exhibited as negative decibels. 

Myth 5: Decibels Have Standard Values

It is important to remember that the loudness or intensity of sound is subjective, depending from person to person. Although decibels offer a standardized calculation, they may only partially measure the sound experience for each human ear. 

What is a Decibel (dB) Scale? Different Hearable Sounds Quantified in dB

In this section, you will learn about the decibel scale values of different sound intensities through the chart below. 

Decibel ValuesSubject
20 dB to 40 dBWhispers, sounds of crickets, mice, etc.
41 dB to 80 dBQuiet speech, small car sounds, normal conversation, and loud conversation
81 dB to 120 dBBaby’s cry, road drills, music events, rock concerts, and shouting out of pain
121 dB to 140 dBJet engine and more


The simplest way to understand what is dB is to define it as a way to calculate sound intensity. Decibels (dB) are measuring units widely used in the audio field. This includes understanding the quietness or loudness of studio music and live shows. However, decibels also play a key role in other areas, such as engineering, telecommunication, and workplace safety. dB has several reference levels. Some common decibel measurements include SPL, SNR, frequency response, SEL, and gain. Moreover, decibels are used for daily chores of life to make better living standards.


Q1. What is the meaning of decibel in sound?

A decibel (dB) is known as a logarithmic unit to measure sound intensity. 

Q2. What is a good dB for sound?

Sounds at 70 dB or below are good and safe for hearing.

Q3. Is 70 dB loud for music?

No, 70 dB is not considered extremely loud for music. 

Q4. Can I listen to 80 dB sound?

Yes, you can listen to an 80 dB sound, but only for up to 40 hours per week.