From CSISWiki
Jump to: navigation, search



Noise can be defined as extraneous, unwanted signals that invade an electrical or optical system. It can also be defined as a sound that is loud, unpleasant, unexpected, or undesired, or any signal that does not convey useful information. Noise is, to a great extent, a purely subjective personal phenomenon. It can be found in almost every area of the world we live in today. It also plays a part in most scientific and electronic fields, albeit sometimes an unwanted part.


In electronics, noise can come from strong electrical or magnetic signals in nearby lines, usually from poorly fitting electrical components. Electronic Noise exists in all circuits and devices as a result of Thermal Noise. It is also an unwanted signal characteristic of all electronic circuits. One section of electronic noise is Shot Noise, this is a form of noise caused by the fluctuations of electric current, and along with Thermal Noise (also known as Johnson Noiseor Nyquist Noise) is the only form of electronic noise inherent to all electronic instruments. Electrical noise limits the sensitivity of radio receiving systems and, when present at high enough levels, may cause false outputs from digital circuits. A simplified explanation of electronic noise is the following: Imagine that you are in a really big room, which is very quiet. Way across the room somebody is whispering and you want to hear them from where you are. You put a microphone in front of you, with an amplifier, and make the amplifier amplify a lot, trying to make that tiny voice become loud enough to hear. In the end you cannot just amplify endlessly, all you will be amplifying is electronic noise. You pick up that 'hummmm' in the speakers, and you don't hear the tiny voice across the room -- it's there on the speakers, but it is drowned out by the noise from the electronics.


With optics, noise can come from the stray reflections of light that emit from various components in the optical system. Noise also affects optical detection systems where light is treated by the particle, or quantum, theory. The output voltage of an optical detector is proportional to the intensity of the incident light.


In Acoustics, noise is defined as any undesirable sound that is intrinsically objectionable or one that interferes with other sounds that are being listened to. Acoustic noise is any unwanted sound in the acoustic domain, including noise pollution, noise on audio systems, appliance noise, factory noise, crowd noise and so on. The physical phenomenon can be measured and thus used in technical specification, while the psycho acoustical characteristic attempts to judge the effect of noise on human beings.

Noise in The Environment

In industries that use small cooling fans, fan noise simply interferes with the ability of the people working nearby to concentrate on their work. Environmental Noise is unwanted sound that disrupts the environment. It has become an increasing problem in modern times due to high noise production in industry by and also by cars and other forms of transportation. These are among the highest producers of environmental noise in a modern urban environment.

There are three main types of Environmental Noise:

  • Continuous Noise: Noise, which is produced by machinery, that operates without interruption.
  • Intermittent Noise: Noise that increases and decreases rapidly from a single event such as an aeroplane flying over.
  • Impulsive Noise: Noise from impacts or explosions such as a gunshot. This type of noise also has a startling effect due to its impulsiveness.

Health Effects Of Noise

Noise has been proven to cause permanent hearing damage to both human and animal hearing systems. Noise can also:

  • Hinder speech communication.
  • Impede thinking process.
  • Interfere with concentration.
  • Obstruct activities.
  • Cause headaches

There is also evidence to suggest that noise can lead to cardiovascular disease through hypertension caused by noise annoyance.













Personal tools