Dhristi JEE 2022-24

What is Noise?

We know that sound is a form of energy. Sound is a mechanical wave and the study of sound starts with the properties of sound waves and the types of sound waves. Basically, the sound is generated in the form of a wave or vibration. Human ears are extremely sensitive to sound waves ranging from 20Hz to 20KHz, known as audible sound range. There are many categories of acoustical sound such as pleasant sound, unpleasant sound, music, noise, soft, loud, etc. 

Now, noise is also a type of sound, it is really important to distinguish between what we mean by noise and what is sound. Noise is a type of sound and it can be explained or defined as a type of sound that can be unpleasant, unwanted, annoying or too loud for human ears. Noise acoustics will help us in understanding what is noise and how it can be reduced. In this article, we will discuss noise and noise acoustics by understanding how noise is produced and different types of noises.

Noise Acoustics

We know that human ears are highly sensitive and excellent at recognizing noise. Generally, noise is a kind of unpleasant and annoying tone of sound that causes mild to major discomfort or sometimes it may lead to irritation. These noise sound vibrations are capable of piercing through the ground noise that accompanies our lives. When it comes to the measuring of the various sorts of noise, we would like to duplicate how the human ear identifies and recognizes any kind of noise to urge an accurate interpretation of its impact. 

Thus, generally, in noise acoustics, we use something called the A-weighted frequency, which is considered to be much more sensitive between the frequencies 500 Hz and 6 kHz range. Depending on these frequency range there are four different types of noises, as listed below:

  • Continuous noise

  • Intermittent noise

  • Impulsive noise

  • Low-frequency noise

Let’s discuss the four sorts of noise one by one as follows:

1. Continuous Noise:

According to the name of the type of noise, we can say it is a kind of noise that is produced continuously. The specimens used or any sample of continuous noise are all mainly caused due to the machines that run continuously with no breaks in between, just like while riding a car we hear the sound of functioning parts especially such as the sound of an engine. The main source of continuous noise could be the production factories, we have seen that in factories large machinery produce continuous noise such that barely we can hear anything else.

2. Intermittent Noise:

  • The intermittent noises are such sound frequencies that are not produced continuously. At the same time, the intermittent noises are produced continuously but with particular intermediate breaks.

  • The best day to day illustration and example of the intermittent noises are the drilling machines, which we would have seen during the destruction or construction of any kind of building. The drilling machines are used to drill the ground and these machines reproduce unbearable sound.

  • Another best and relative example of intermittent noise is drilling machines employed by a carpenter or the dentist.

3. Impulsive Noise:

  • The impulsive noise is a kind of noise characterized by a background level of audible range up to 40dB in less than a half-second with a duration of 1 second.

  • Impulsive noises mainly include almost all unwanted, unpleasant and instantaneous sharp sounds.

  • The best examples of impulsive noises are bomb explosions that are terrifying and unbearable, the perimeter of weapons, and so on.

4. Low-Frequency Noise:

  • The low-frequency noises are generally produced from the items available in our surroundings in our everyday life. The low-frequency noise is one of the complicated types of noise to scale back, and even if it is measured in a silent room still it would register sound levels around only 30-40 decibels.

  • The low-frequency noise can be noticed in an office setting, this noise might have been produced from heating or ventilation. In domestic cases, it will arise from the ticking on a timepiece or wall clock. Usually, we can not even recognize these sorts of noises unless we direct our attention towards them.

So, these are the various types of noises and what is the meaning of noise physics. In analogue electronics and network theory, the word noise refers to those random, unpredictable, and undesirable signals, or mutations in signals, that cover the specified and desired information and the content. At the same time noise in the radio signal transmission seems to be as a static wave and in television signals as snow. depending on the complexity levels, the noises are subdivided into white noise and pink noise. Let us have a look at these two one-by-ones.

A. White Noise:

The white noise may be referred to as a complex signal or sound wave that incorporates the whole range of audible frequencies, all of which possess equal intensity. White noise is identical to white light, which contains merely equal intensities of all frequencies of light present in nature. A good approximation to white noise is that the static waves found in between the radio stations on the FM band.

B. Pink Noise:

The pink noise includes all the frequencies of the audible spectrum but with an intensity that will considerably decrease with increases in frequency at a rate of three decibels per octave. This decrease in frequency roughly corresponds there to acoustic (non-electronic) musical instruments or ensembles. Thus, the pink noise has been used in checking the listening rooms and particularly for auditoriums for his or her acoustic characteristics and parameters, such as reverberation time, sound-absorbing, and undesirable resonance behaviour which are the most important parameters in noise acoustics. It can also be used in audio equalizers to supply a linear intensity versus frequency response within the available listening environment.

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Any kind of noise can be eliminated by providing the rooms with sound proof walls or by sound blocking. These days acousticcurtains are constructing the building by keeping the acoustic soundproofing walls for the buildings and auditoriums.

Did You Know?

1. The Maximum Loudest Sound the Earth Has Ever Produced: 

The loudest natural sound or the noise on Earth are produced by erupting volcanoes. In the year 1883, the volcano eruption that took place on Krakatoa is considered to be the loudest noise that had been produced on Earth. 

2. The Noisiest City in the World: 

According to the recent survey and the research conducted by City Quiet, the top three noisiest cities in the entire world are Mumbai (India), Kolkata (India) and Cairo (Egypt). These cities are also subjected to maximum noise pollution due to the same reason.

3. The Loudest Animal on Earth: 

Even though we have heard that the call of a blue whale reaches 188 decibels, which is even louder than a jet engine or any grenade explosion, yet the loudest animal on Earth is the sperm whale whose communicative signals have been measured about up to 230 dB.

4. We have to consider an important fact that the root and main source of noise in urban environments: According to the survey and research of a European Environment Agency (EEA) briefing ‘Managing exposure to noise in Europe’, the transport sector is a major reason for noise pollution. Road traffic is the predominant noise source affecting approximately around 100 million people in the 33 member countries of the EEA.

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FAQs (Frequently Asked Questions)

1. What are the Four Types of Noise?

Ans: There are four different types of sound, as listed below:

  • Continuous noise

  • Intermittent noise

  • Impulsive noise

  • Low-frequency noise

2. What is Noise Control in Acoustics?

Ans: Basically the Noise control in acoustics or noise regulations in acoustics is a set of strategies to reduce the noise pollution percentage or to reduce the impact of that noise, whether outdoors or indoors.

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