# Calculations

Aerodynamics

Drag Coefficient
A dimensionless value that allows the comparison of shape and orientation of different bodies.
Kinematic Viscosity
The dynamic viscosity of a fluid divided by the fluid density.
Vehicle Aerodynamic Drag
Resistance of a vehicle body to motion through the air.
Viscosity
A measure of the internal friction within a fluid.

Algebra

Antilogarithm
x=by is called the antilogarithm of y to the base b.
Briggsian Logarithm
Another name for the Common Logarithm.
Common Logarithm
Logarithm in which the base is 10.
Cubic Equation
An equation of the third order.
Logarithm
The power to which a base must be raised to yield a given number.
Napierian Logarithm
Another name for the Natural or Common Logarithm.
Natural Logarithm
Logarithm in which the base is e.
An equation of the second order.

Architectural Acoustics

Acoustic Cavity
The acoustics of enclosed volumes are important when considering sound propagation within the volume.
A Weighting
This is the most generally used filter when making overall noise measurements.
Cavity Acoustics
The acoustics associated with enclosed volumes.
Decibel
The human ear responds logarithmically and it is convenient to deal in logarithmic units in audio systems.
Room Modes
Frequencies at which sound waves in a room resonate (in the form of standing waves), based on the room dimensions.
Sound Transmission Class
In acoustics, a single number rating for describing sound transmission loss of a wall or partition.

Architecture

Room Modes
Frequencies at which sound waves in a room resonate (in the form of standing waves), based on the room dimensions.

Audio

Acoustic Cavity
The acoustics of enclosed volumes are important when considering sound propagation within the volume.
A Weighting
This is the most generally used filter when making overall noise measurements.
Bark
The Bark is the standard unit corresponding to one critical band width of human hearing.
B Weighting
The B-weigthing curve approximately follows the 70 phon curve.
Circular Frequency
C Weighting
The C-weighting curve approximately follows the 100 phon curve.
dBA
A sound-level meter reading with an A-weighting network simulating the human-ear response at a loudness level of 40 phons.
dBB
A sound-level meter reading with a B-weighting network simulating the human-ear response at a loudness level of 70 phons.
Decibel
The human ear responds logarithmically and it is convenient to deal in logarithmic units in audio systems.
Quarter Wave Tube
A resonator used most commonly on automotive air intake systems to reduce resonance.
Sound Transmission Class
In acoustics, a single number rating for describing sound transmission loss of a wall or partition.
Speed of Sound
Depends on the elastic and inertial properties of the particular medium.

Automotive

Some empirical noise prediction models have been derived from a sample of 1m radiated engine noise measurements.
Fuel Consumption
Definitions of fuel consumption calculations.
litres per 100km
Unit of fuel consumption used in the automotive industry.
mile per gallon
Fuel consumption.
Wheel
The Mesopotamians are credited with the invention of the wheel.

Civil Engineering

Cantilever Beam
A beam that is held in an encastre at one end whilst the other end is unsupported.

Classical Mechanics

Acceleration
The change in velocity divided by the time it takes to make the change.
Angular Frequency
Angular Momentum
A vector quantity giving the rotational momentum.
Angular Velocity
The rate of change of angle turned in radians.
Escape Velocity
This is the initial velocity that an object would have to have if projected from the surface of a body (e.g. Earth) to reach infinity before coming to rest.
Kinetic Energy
The energy that a body possesses solely because it is moving.
Linear Momentum
A vector quantity equal to the product of an object's mass and its velocity.
Torque
The torque or turning moment acting on a body is defined as the product of the magnitude of the force and the perpendicular distance of the line of action of the force from the axis about which the body is being rotated.

Electronics

B
An abbreviation of bel, the logarithm of the ratio of two powers. The decibel is one tenth of a bel.
bel
The bel is the logarithm of the ratio of two powers, and the decibel is one tenth of a bel.
Decibel
The human ear responds logarithmically and it is convenient to deal in logarithmic units in audio systems.
Resistance
The electrical resistance of a conductor.
Resistor
Passive component with a known resistance. The value of resistance is usually shown by a set of coloured bands on the body of the component.

Engines

Some empirical noise prediction models have been derived from a sample of 1m radiated engine noise measurements.
Fuel Consumption
Definitions of fuel consumption calculations.

Fluid Dynamics

Drag Coefficient
A dimensionless value that allows the comparison of shape and orientation of different bodies.
Dynamic viscosity
That molecular property of a fluid which enables it to support tangential stresses for a finite time and thus to resist deformation.
Kinematic Viscosity
The dynamic viscosity of a fluid divided by the fluid density.
Vehicle Aerodynamic Drag
Resistance of a vehicle body to motion through the air.
Viscosity
A measure of the internal friction within a fluid.

Geometry

Circle
The set of points equidistant from a given point.
Sphere
Basic calculations of the properties of a sphere.
Square
A number raised to the power 2 ie 2 x 2 = 22 = 4. Also, a 2 dimensional figure with the height and width having the same lengths,and at right angles to each other.

Mathematics

Angular Frequency
Averaging
In any process it is often necessary to average a number of measurements to gain any confidence in the measured value.
Cylinder
A right angle circular cylinder.
Factorial
Definition of factorial.
ln
Abbreviation of Natural Logarithm.
log
Abbreviation of Logarithm.
Pythagoras Theorem
The Square on the Hypotenuse is equal to the sum of the squares of the other two sides.
Square
A number raised to the power 2 ie 2 x 2 = 22 = 4. Also, a 2 dimensional figure with the height and width having the same lengths,and at right angles to each other.
Square Root
The square root of a number is a number that when multiplied by itself equals the number that the square root is being taken of.

Mechanical Engineering

Cantilever Beam
A beam that is held in an encastre at one end whilst the other end is unsupported.
Cutting Speed
The surface speed of the workpiece in a lathe or a rotating cutter.
Froude Number
A dimensionless number used in the study of fluid flow problems with models.
Leaf Springs
Either a simple beam used as a spring or laminations of steel.
Moments of Inertia
Principal axes for bodies of uniform density.
mpg
Abbreviation of mile per gallon.
Prandtl Number
A dimensionless group often used in heat exchange calculations.
Quarter Wave Tube
A resonator used most commonly on automotive air intake systems to reduce resonance.
Reynolds Number
This is a non-dimensional number (consistent units) which describes whether fluid flow is laminar, turbulent, or transitional between the two.
Springs
The physics of simple springs - helical and beam forms.
Thin Rod
The moment of inertia of a thin rod.
Torque
The torque or turning moment acting on a body is defined as the product of the magnitude of the force and the perpendicular distance of the line of action of the force from the axis about which the body is being rotated.
Wheel
The Mesopotamians are credited with the invention of the wheel.

Noise & Vibration

Acoustic Cavity
The acoustics of enclosed volumes are important when considering sound propagation within the volume.
Angular Frequency
Articulation Index
A quantitative measure of the intelligibility of speech; the percentage of speech items correctly perceived and recorded.
A Weighting
This is the most generally used filter when making overall noise measurements.
B
An abbreviation of bel, the logarithm of the ratio of two powers. The decibel is one tenth of a bel.
Bandwidth Time Product
Used in calculating the confidence limit of a measurement.
Bark
The Bark is the standard unit corresponding to one critical band width of human hearing.
bel
The bel is the logarithm of the ratio of two powers, and the decibel is one tenth of a bel.
B Weighting
The B-weigthing curve approximately follows the 70 phon curve.
Cavity Acoustics
The acoustics associated with enclosed volumes.
Circular Frequency
Coincidence
The sound radiation efficiency of a plate is dependant upon the coupling of sound waves in the air and flexural waves (vibration) in the plate. Optimum efficiency (maximum energy transfer from vibration to sound or visa versa) is achieved when the plate is vibrated such that the wavelength of flexural waves in the plate is equal to the wavelength of acoustic waves in the air.
C Weighting
The C-weighting curve approximately follows the 100 phon curve.
Decibel
The human ear responds logarithmically and it is convenient to deal in logarithmic units in audio systems.
Some empirical noise prediction models have been derived from a sample of 1m radiated engine noise measurements.
Expansion Chamber
The expansion chamber can be considered as a simple low pass filter.
Octave
Two frequencies are an octave apart if the ratio of the higher frequency to the lower frequency is two.
Quarter Wave Tube
A resonator used most commonly on automotive air intake systems to reduce resonance.
Room Modes
Frequencies at which sound waves in a room resonate (in the form of standing waves), based on the room dimensions.
Single Acoustic Barrier
A single layer acoustic barrier.
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 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 Transmission Class
In acoustics, a single number rating for describing sound transmission loss of a wall or partition.
Speed of Sound
Depends on the elastic and inertial properties of the particular medium.
Strouhal Number
A dimensionless unit.
Wavelength
The shortest repetition length for a periodic wave.
Wavenumber
Wavenumber describes the spatial variation of waves, phase change per unit distance.

Optics

Pockels Cell
A Pockels Cell is a device which contains a photo refractive crystal. When a voltage is applied to this crystal it can change the polarisation or phase of the light beam.
Snells Law
Snells law defines the angle of refraction of a light beam when it passes from one medium to another.

Physics

Averaging
In any process it is often necessary to average a number of measurements to gain any confidence in the measured value.
Conical Pendulum
The motion of the wire from which the bob hangs describes the surface of a cone.
Equations of Motion
There are four basic equations that describe the motion of a body moving with constant acceleration.
Frequency
The rate of repetition of periodic motion measured in hertz (cycles per second).
Froude Number
A dimensionless number used in the study of fluid flow problems with models.
Gravitational Potential
The worrk done in bringing a unit mass from infinity to that point. The assumption being that the gravitational potential is zero at infinity.
Gravitational Potential Energy
The work done by the force of gravity when an object falls from a particular point in space to the location assigned the value of zero.
Julian Day
Instituted by J. Julius Scaliger in 1582. The Julian date is independent of various calendars and chronological events.
Length Contraction
An observer in motion relative to an object measures the length of that object along the direction of motion to be contracted when compared to the length measured by an observer at rest relative to the object.
Mach Number
The ratio of the speed of a body or flow of a fluid to the local speed of sound in the fluid.
Moments of Inertia
Principal axes for bodies of uniform density.
Newton′s Law of Universal Gravitation
Every particle in the Universe attracts every other with a force which is proportional to the product of their masses and inversely proportional to the square of their seperation.
Ohm
Defined as the resistance of a conductor through which a current of one ampere is flowing when the potential difference across it is one volt.
Pendulums
There are a number of different forms of pendulum. The main characteristic being that when the mass is displaced from it's position of rest it will oscillate at a fixed frequency.
Prandtl Number
A dimensionless group often used in heat exchange calculations.
Relativistic Kinetic Energy
The energy that a body possesses solely because it is moving.
Resistance
The electrical resistance of a conductor.
Reynolds Number
This is a non-dimensional number (consistent units) which describes whether fluid flow is laminar, turbulent, or transitional between the two.
Simple Pendulum
The mass hung on a fine wire, displaced from rest and released.
Snells Law
Snells law defines the angle of refraction of a light beam when it passes from one medium to another.
Speed of Sound
Depends on the elastic and inertial properties of the particular medium.
Strouhal Number
A dimensionless unit.
Thin Rod
The moment of inertia of a thin rod.
Wavelength
The shortest repetition length for a periodic wave.
Wavenumber
Wavenumber describes the spatial variation of waves, phase change per unit distance.
Wheel
The Mesopotamians are credited with the invention of the wheel.

Signal Processing

Bandwidth Time Product
Used in calculating the confidence limit of a measurement.
Circular Frequency

Tools

Cutting Speed
The surface speed of the workpiece in a lathe or a rotating cutter.

Transport

Vehicle Aerodynamic Drag
Resistance of a vehicle body to motion through the air.

Trigonometry

Cosine
Trigonometric function.
Sine
Trigonometrical function.
Tangent
Trigonometric function.

Units

Decibel
The human ear responds logarithmically and it is convenient to deal in logarithmic units in audio systems.
Pound Force Foot
The unit of torque in the old British system of units, abbreviated lbf ft.