Nobelium is a man-made element with an atomic number of 102.
Chemical formula for Nitric Oxide.
Chemical formula for Nitrogen Dioxide.
Nobel Prize
Awarded annually as per Alfred Nobel′s last will and testament.
A man-made element with an atomic number of 102.
Noble Gases
The gaseous chemical elements helium, neon, argon, krypton, xenon and radon, which are all placed in Group 0 of the Periodic Table.
Noble Metals
Metals, such as gold, silver and platinum, that show a marked reluctance to combine with other elements to form compounds.
Noctilucent Clouds
Rarely seen clouds of tiny ice particles that form approximately 75 to 90 kilometers above the earth′s surface.
A point or line on a vibrating structure that remains stationary.
Noether Theorem
Demonstrates that symmetries are what gives rise to conserved quantities.
Noise is any undesired signal.
Noise & Vibration
Lists all the Noise & Vibration topics
Noise & Vibration Books
Lists all Noise & Vibration Books in the Encyclopaedia
Noise & Vibration Calculations
Lists all Noise & Vibration Calculations in the Encyclopaedia
Noise & Vibration Conversions
Lists all Noise & Vibration Conversions in the Encyclopaedia
Noise & Vibration Weblinks
Lists all Noise & Vibration Weblinks in the Encyclopaedia
Noise Climate
This is sometimes calculated as LA10 - LA90 and represents the fluctuations in noise.
Noise Control
The technology of obtaining an acceptable noise environment.
Noise Criteria
Standard spectrum curves by which a given measured noise may be described by a single NC number.
Noise Exposure Forecast
There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Noise Exposure Levels
There are a number of different calculations for exposure levels for different times of the day, environment and types of noise source.
Noise Exposure Limits
The amount of hearing loss is dependent on the noise level and duration.
Noise Figure
The ratio of the noise power in the output of an amplifier to that part of the output noise power that is due solely to the noise in the input signal.
Noise Floor
Normally the lowest threshold of useful signal level.
Noise Generator
A piece of equipment used to produce random electrical noise.
Noise Induced Hearing Loss
A sensor-neural loss attributed to the effects of noise.
Noise Isolation Class
A single-number rating calculated in accordance with Classification E 413 using measured values of noise reduction. It provides an estimate of the sound isolation between two enclosed spaces that are acoustically connected by one or more paths.
Noise Level
For airborne sound , unless specified to the contrary, it is the A-weighted sound level.
Noise Path Analysis
An analysis technique that uses noise transfer functions, mount stiffness and input force calculations to determine the dominant noise paths for any particular frequency range or operating condition.
Noise Pollution
Unwanted noise, including traffic noise, machinery noise or music.
Noise Pollution Level
There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Noise Rating Curves
Developed by the International Standards Organisation in 1971 to rate noisiness with the 1000 Hz octave band as reference point.
Noise Reduction
The difference in sound pressure level between any two points along the path of sound propagation. As an example, noise reduction is the term used to describe the difference in sound pressure levels between the inside and outside of an enclosure.
Noise Reduction Coefficient
Arithmetic mean of sound absorption coefficients.
Noise Reduction Rating
Indicates a hearing protectors noise reduction capability.
A system for naming things.
Nominal Size
A designated size that may be different from the actual size.
Nominal Stress
Stress calculated on the basis of the net cross section of a specimen without taking into account the effect of geometric discontinuities such as holes, grooves, fillets, etc.
Nominal System Voltage
A nominal value assigned to designate a system of a given voltage class.
A graphical device used for computation which uses a straight edge and several scales of numbers.
A nine sided polygon.
Nonagonal Number
A number of the form n(7n-5)/2.


A colourless volatile liquid, an ingredient of ordinary kerosene.

Associated with 9.
Not carrying a load.
Noncondensable Gas
A gas whose temperature is above its critical temperature, so that it cannot be liquefied by increase of pressure alone.
Non-Contact Bearing
A bearing in which no solid contact occurs between relatively moving surfaces.
The solid state wherein there is no long-range atomic order. Sometimes used synonymously with the terms amorphous, glassy and vitreous.
Nondegenerative Parametric Amplifier
A parametric amplifier that uses a pump signal frequency that is higher than twice the frequency of the input signal.
Non-Destructive Hydrogenation
Hydrogen is added to a molecule that is unsaturated with respect ot hydrogen.
Non-Destructive Testing
A method in which the part is stimulated and its response measured quantitatively or semiquantitatively.
Nondeterministic Signal
For a nondeterministic signal the physical phenomenon cannot be represented mathematically.
Nondimensional Number
A pure number not involving any physical dimensions.
Nondimensional Parameter
Any parameter of a problem which has the dimensions of a pure number, usually rendered so deliberately.
A substance which does not ionize in solution.
Metals which contain no iron. Aluminum, brass, bronze, copper, lead, nickel, and titanium are nonferrous.
A number equal to 1030.
Non-Impulsive Noise
All noise not included in the definition of impulsive noise.
Noninertial Reference System
Any reference system in which the law of inertia is not valid.
Non-Ionizing Radiation
Radiation without enough energy to remove tightly bound electrons from their orbits around atoms.
Nonlinear Damping
Damping due to a damping force that is not proportional to velocity.
Nonlinear Device
A device in which the output does not rise and fall in direct proportion to the input.
Nonlinear Distortion
New spectral components are produced.
Nonlinear Impedance
An impedance in which the resulting current through the device is not proportional to the applied voltage.
Nonluminous Bodies
Objects that either reflect or diffuse light that falls upon them.
Nonmaskable Interrupt
A hardware interrupt that software cannot disable.
A term usually reserved for those chemical elements that are very poor electrical conductors in the solid state and liquid states.
Non-Newtonian Fluid
A fluid whose viscosity changes when the gradient in flow speed changes.
Having a relatively even or symmetrical distribution of charge.
Nonpolar Molecule
A molecule in which the center of positive charge and the center of negative charge coincide.
Non-Reference Oil
Any oil other than a reference oil; such as a research formulation, commercial oil or candidate oil.
Nonsingular Matrix
A square matrix A is nonsingular if the only solution to the equation Ax = 0 is x = 0.
Non-Specular Surface
A surface which is diffuse, meaning it reflects light in equal amounts in all directions.
A characteristic of a time series for which the distribution changes over time.
Non-Steady State Diffusion
The diffusion condition for which there is some net accumulation or depletion of diffusing species; the diffusion flux is dependent on time.
Nonvolatile Memory
A type of memory that retains information without electrical power.
Nor Gate
Gate whose output is 0 if any of its inputs is a 1.
Nordic Gold
A 89% copper, 5% aluminium, 5% zinc and 1% tin alloy.

A line perpendicular to a surface or curve.
Normal Concentration
Used in chemistry to describe a solution having a concentration of 1 gram equivalent per litre.
Normal Distribution
A continuous probability distribution that often gives a good description of data that cluster around the mean. Also known as Gaussian Distributon or Bell Curve.
Normal Emittance
Emittance in a direction perpendicular to the surface or in a small solid angle whose axial ray is perpendicular to the surface.
Normal Litre
A unit of mass for gases equal to the mass of 1 litre at a pressure of 1 atmosphere and at a standard temperature, often 0°C or 20°C
Normal Mode of Vibration
A mode of free vibration of an undamped system. In general, any composite motion of a vibrating system ban be analyzed into a summation of its normal modes.
Normal Stress
Stress acting perpendicular to an imaginary plane cutting through an object.
Normalized Noise Isolation Class
A single-number rating calculated in accordance with Classification E413 using measured values of normalized noise reduction.
Normalized Noise Reduction
Between two rooms, in a specified frequency band, the value that the noise reduction in a given field test would have if the reverberation time in the receiving room were 0.5s.
Heating a ferrous alloy to a suitable temperature above the transformation range and then cooling in air to a temperature substantially below the transformation range.
Normally Aspirated Engine
An engine that uses intake air at atmospheric pressure and temperature to mix with the fuel for combustion.
Style of buildings erected by the Normans 1066 to 1154 based on the Italian Romanesque.
Norris Eyring Formula
A formula for calculating the reverberation time of a room based on the absorption coefficient of the walls, surface area and volume.
North Atlantic Oscillation
Consists of opposing variations of barometric pressure near Iceland and near the Azores.
North Pole
That end of the axis of rotation of a celestial body at which, when viewed from above, the body appears to rotate in a counter-clockwise direction.
Northern Lights
Common name for the Aurora or Aurora Borealis, a faint visual phenomenon associated with geomagnetic activity.
North-South Engine Layout
Another expression for a Longitudinal Engine layout.
Norton Surface Wave
The ground-wave component of a space wave resulting from refraction of a portion of the reflected-wave component at the Earth-atmosphere interface and induction of electrical currents in the ground.
Abbreviation of Network Operating System.
not equal to
A definite statement that the quantity on the left hand side is not equal to the quantity on the right hand side.
Not Gate
Logic element that acts as an inverter.
Notch Filter
An electronic network which passes signals having frequencies above and below the band-elimination frequency span.
A star which suddenly becomes many times brighter than previously, and then gradually fades.
Abbreviation of Nitrogen Oxides where x represents a varying proportion of oxygen.
Unit of perceived noisiness.