Chemical formula for Sulphur Dioxide.
A salt of a fatty acid.
Abbreviation of State of Charge.
Loss of hearing caused by noise exposures that are part of the social environment, exclusive of occupational-noise exposure, physiological changes with age, and disease.
Socket Bolt
Fastened with a hexagonal Allen key.
Socket Wrench
A tool with socket end or a drive tool combined with a socket.
Greek philosopher; emphasized the study of human nature in relationship to society.
Soda Ash
Alternative name for Sodium Carbonate.
A soft, silvery coloured metal which, like other members of the alkali group of metals, is extremely reactive.
Sodium Carbonate


Commonly known as washing soda or soda ash. Synthetically produced in large quantities from common salt using the Solvay process.

Sodium Chloride


Commonly known as table salt.

Sodium Filled Exhaust Valves
The valve stem is drilled and partially filled with sodium to increase heat transfer to the valve guide and hence reduce the temperature of the exhaust valve.
Sodium Glutamate
More commonly known as Monosodium Glutamate.
Sodium Hydride


White to silver coloured solid.

Sodium Hydroxide


A caustic metallic base used in the manufacture of pulp, textiles, drinking water, soaps and detergents.

Sodium Hypochlorite


Sold as a solution under a variety of trade names for use as liquid bleach.

Sodium I Bromide


White crystalline solid.

Sodium I Fluoride


White crystalline solid.

Sodium I Iodide


White crystalline solid.

Sodium I Oxide


Yellow crystalline solid.

Sodium Nickel Chloride Battery
This consists of a negative liquid sodium electrode and a solid positive electrode containing nickel chloride and nickel.
Sodium Nitrate


A white solid which is very soluble in water, used as an ingredient in fertilizers, explosives, and in solid rocket propellants, as well as in glass and pottery enamels.

Sodium Oxide


White solid.

Sodium Peroxide


Pale yellow solid.

Sodium Silicate


Available in aqueous solution and in solid form and is used in cements, passive fire protection, refractories, textile and lumber processing, and automobiles.

Sodium Sulphur Battery
Uses a solid electrolyte of beta aluminium and liquid electrodes of molten sulphur and sodium.
Sodium Superoxide
Old name for Sodium I Oxide.
Abbreviation of Solid Oxide Fuel Cell.
The undersurface of a horizontal element of a building, especially the undersides of a stair or roof overhang.
Soft Foot
A term used to describe any condition where tightening or loosening the bolts of the machine feet distorts the machine frame.
Soft Room
Room with highly sound absorptive surfaces.
Soft Solder
Solder composed of 50% Tin and 50% Lead
Soft X-Rays
Band of low energy X-rays, between 0.1 keV and approximately 5 keV.
Soft-Ground Tunnel
A passage constructed through loose, unstable, or wet ground, requiring supports to keep the walls from collapsing.
Soil Bulk Electrical Conductivity
Conductivity of electricity through soil.
Soil Heat Flux
The amount of heat flowing into a cross-sectional area of soil per unit time.
Soil Volumetric Water Content
The proportion of a volume of soil that is water.
A colloid with solid particles suspended in a liquid.
Solar Air Mass
The optical air mass penetrated by light from the sun for any given position of the sun in the sky.
Solar Cell
A cell that produces current under sunlight.
Solar Cell Efficiency
The ratio of the electric power produced by a photovoltaic device to the power of the sunlight incident on the device.
Solar Constant
The bolometric flux at a distance of 1 AU from the sun = 1.368x103Wm-2
Solar Cycle
The approximately 11 year quasi-periodic variation in frequency or number of solar active events.
Solar Data
Equatorial radius, mass, solar constant,…
Solar Day
The day defined as one revolution of the Earth on its axis with respect to the Sun.
Solar Eclipse
When the Earth enters the Moon′s shadow as the Moon moves wholly or partially in front of the Sun as seen from Earth.
Solar Energy
Electromagnetic energy transmitted from the sun.
Solar Flare
Sudden violent explosion on the Sun which occurs above complex active regions in the photosphere.
Solar Irradiance
The direct, diffuse, and reflected solar radiation that strikes a surface. Usually expressed in kilowatts per square meter. Irradiance multiplied by time equals insolation.
Solar Noon
The time of the day, at a specific location, when the sun reaches its highest, apparent point in the sky; equal to true or due geographic south.
Solar Power System
Concept for providing large amounts of electricity for use on the Earth from one or more satellites in geosynchronous Earth orbit.
Solar Protons
Protons emitted by the sun, especially during solar flares.
Solar Resource
The amount of solar insolation a site receives, usually measured in kWh/m2/day, which is equivalent to the number of peak sun hours.
Solar Spectrum
The total distribution of electromagnetic radiation emanating from the sun.
Solar Storm
Violent outburst of explosive activity on the Sun.
Solar System
Meaning our sun and all of the bodies that orbit the sun.
Solar Wind
The wind from the Sun. More specifically, particles, usually electrons and protons, continually streaming away from the corona of the Sun.
A low melting point alloy that can wet copper, conduct current, and mechanically join conductors.
Solder Balls
Small spheres of solder adhering to the laminate, mask, or conductor surfaces usually after wave or reflow soldering.
Solder Bridging
When solder paste or solder on two or more adjacent pads come into contact to form a conductive path or bridge.
Solder Mask
A dielectric material used to cover the entire surface, except where the joints are to be formed, of a PCB primarily to protect the circuitry from environmental damage.
Solder Paste
Mixture of minute spherical solder particles, activators, solvent, and a gelling or suspension agent.
Process of joining metallic surfaces with solder without melting the base material.
Soldering Iron
A tool with a handle attached to a copper or iron tip which is heated, electrically or in a flame, and used to melt solder to make joints.
A brick laid on its end, with its narrow face toward the outside of the wall.
An electromagnetic device that changes electrical energy into mechanical motion.
Matter with a definite size and shape.
Solid Axle
Suspension where left and right wheels are rigidly connected except torsionally.
Solid Brake Disc
A brake disc that is solid metal between its friction surfaces.
Solid Geometry
The study of figures in three-dimensional space.
Solid Height
The height of a coil spring when it is totally compressed to the pont at which each coil touches the adjacent coil.
Solid of Revolution
A solid formed by rotation a plane figure about an axis in three-space.
Solid Oxide Fuel Cell
A fuel cell that employs a solid, ionically conductive material as electrolyte.
Solid Rocket
A rocket that uses a solid propellant.
Solid Solution
A single solid homogeneous crystalline phase containing two or more chemical species.
Solid State Device
An electronic device that operates by the movement of electrons within a solid piece of semiconductor material.
The change from liquid state to solid state upon cooling through the melting temperature or melting range.
Solidification Range
The temperature between the liquidus and solidus.
Solidification Shrinkage Crack
A crack that forms due to internal stresses developed from shrinkage during solidification of a metal casting; also called a hot crack.
In a constitution or equilibrium diagram, the locus of points representing the temperatures at which various compositions finish freezing on cooling or begin to melt on heating.
The solubility of a substance is its concentration in a saturated solution.
Solubility Product
The equilibrium constant for a reaction in which a solid ionic compound dissolves to give its constituent ions in solution.
Solubilizing Group
A group or substructure on a molecule that increases the molecule′s solubility.
Capable of being dissolved in a solvent, usually water.
Soluble Salt
An ionic compound that dissolves in a solvent, usually water.
What is dissolved in a solution.
Mixture of a solid and a liquid where the solid never settles out.
Solution Heat Treatment
Heating an alloy to a suitable temperature, holding at that temperature long enough to allow one or more constituents to enter into solid solution, and then cooling rapidly enough to hold the constituents in solution.
Liquid in which something is dissolved, eg the water in saltwater.
Solvent Extraction
A method for separating mixtures by exploiting differences in the solubilities of the components.
The curve on a phase equilibrium diagram that defines the limits of solid solubility.
Somatic Cells
Body cells. All the cells except the germ-line cells.
Sound waves in water.
The unit of measurement for loudness. One sone is the loudness of a sound whose loudness level is 40 phons.
Pertaining to sounds capable of being heard by the human ear.
Sonic Boom
A body moving through the air pushes the air aside. If the body moves at or greater than the speed of sound a sonic boom is observed.
Sonic Delay Line
A device used in a communications link or a computer memory in which the signal is delayed by the propagation of a sound wave. Also known as an Acoustic Delay Line.
An instrument designed to receive sound energy underwater and transmit a corresponding signal in the atmosphere at radio frequencies.
Light emission from small cavitating bubbles of air or other gas in water or other fluids, produced when the fluid is acted upon by intense high frequency sound waves.
Sub-micron size particles, primarily carbon, created in combustion as products of incomplete combustion.
To take up gas by sorption.
Gas taken up by a sorbent.
The material which takes up gas by sorption.
Assimilation of molecules of one substance by a material in a different phase.
Energy that is transmitted by pressure waves in air or other materials and is the objective cause of the sensation of hearing.
Sound Absorption
Reduction of sound pressure level through sound absorption.
Sound Absorption Coefficient
The practical unit between 0 and 1 expressing the absorbing efficiency of a material. It is determined experimentally.
Sound Attenuation
The reduction of the intensity of sound as it travels from the source to a receiving location.
Sound Barrier
Concept that the speed of sound, or sonic speed, constitutes a speed limit to flight through the atmosphere.
Sound Definition
This compares ‘useful’ sound with total sound.
Sound Energy
Energy added to an elastic medium by the presence of sound, consisting of potential energy in the form of deviations from static pressure and of kinetic energy in the form of particle velocity.
Sound Energy Density
The quotient obtained when the sound energy in a region is divided by the volume of the region.
Sound Energy Flux
The average rate of flow of sound energy for one period through any specified area.
Sound Energy Flux Density
This is Sound Intensity.
Sound Exposure Level
Used to describe the amount of noise from an event such as an individual aircraft flyover.
Sound Field
A region containing sound waves. Normally broken down into Near Field and Far Field.
Sound Focusing
Focusing of sound can be caused by reflection from large concave surfaces.
Sound Growth
The growth of sound in the room.
Sound Insulation
The capacity of a structure to prevent sound from reaching a receiving location.
Sound Intensity
The quotient obtained when the average rate of energy flow in a specified direction and sense is divided by the area, perpendicular to that direction, through or toward which it flows.
Sound Isolation
The degree of acoustical separation between two locations, especially adjacent rooms.
Sound Level
Of airborne sound, a sound pressure level obtained using a signal to which a standard frequency-weighting has been applied.
Sound Level Meter
Device used to measure sound pressure level.
Sound Masking
The process of using electronic masking sound to cover unwanted or intrusive sound such as speech or equipment noise, typically used to enhance speech privacy and productivity.
Sound Paths
A trace of the path taken by specific sound waves as they move outward from the source of the sound to the receiver location.
Sound Power
In a specified frequency band, the rate at which acoustic energy is radiated from a source. In general, the rate of flow of sound energy, whether from a source, through an area, or into an absorber.
Sound Power Level
Of airborne sound, ten times the common logarithm of the ratio of the sound power under consideration of the standard reference power of 1 pW. The quantity so obtained is expressed in decibels.
Sound Pressure
A fluctuating pressure superimposed on the static pressure by the presence of sound.
Sound Pressure Level
Ten times the logarithm of the ratio of the time-mean-square pressure of a sound to the square of the reference sound pressure.
Sound Propagation
At distances large compared to the size of the source, sound intensity diminishes according to the inverse square law.
Sound Quality
Pertaining to the quality or other aspects of the machine that might be inferred from the sound it makes.
Sound Receiver
One or more observation points at which sound is evaluated or measured. The effect of sound on an individual receiver is usually evaluated by measurements near the ear or close by.
Sound Source
A calibrated source of sound that is used for measurements of the acoustic performance of materials, partitions and complete rooms and buildings.
Sound Transmission Class
In acoustics, a single number rating for describing sound transmission loss of a wall or partition.
Sound Transmission Coefficient
Of a partition, in a specified frequency band, the fraction of the airborne sound power incident on the partition that is transmitted by the partition and radiated on the other side.
Sound Transmission Loss
Of a partition, in a specified frequency band, ten times the common logarithm of the ratio of the airborne sound power incident on the partition to the sound power transmitted by the partition and radiated on the other side.
Sound Waves
Sound waves can be thought of like the waves in water.
Expansion card which enables the PC to make sounds.
Any probe of the environment made to obtain information at various levels.
Sounding Rocket
A rocket that carries aloft equipment for making observations of or from the upper atmosphere.
A listening term that refers to the placement of a stereo image in a fashion that replicates the original performance.
Sour Water
Waste waters containing fetid materials, usually sulphur compounds.
The object that produces the wave or disturbance.
Source Room
In architectural acoustical measurements, the room that contains the noise source or sources.
Source Route
The route that a packet takes to reach its destination. The route is determined prior to the start of the transmission of the packet.
Southern Blot
A DNA hybridization procedure in which specific DNA fragments are detected in a mixture by means of a complementary, labelled nucleic acid probe.