The rate of change of angle turned in radians. where = angular velocity [rads-1] = angle turned [rad] t = time taken [s]

## Revolutions per Second

Unit to describe the rate of rotation of a body. Conversions 1 revolution per second = 1 rev s-1 1 rps = 1 rev s-1 1 rev s-1 = 6.283 rad s-1 1 rev s-1 = 60 rpm

## Revolutions per Minute

Unit to describe the rate of rotation of a body. Abbreviated: rpm Photograph courtesy of industrial-needs.com Conversions 1 revolution per minute = 1 rev min-1 1 rpm = 1 revolution per minute 1 rpm = 0.1047 rad s-1 1 rev s-1 = 60 rpm Some examples are really simple, the second hand of

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## Sound Transmission Class

In acoustics, a single number rating for describing sound transmission loss of a wall or partition. The STC is calculated from the 1/3 octave transmission loss (TL) measurement of the partition over the 1/3 octave centre frequencies from 125Hz to 4000Hz. These 1/3 octave values are compared with a set of reference curves. The curve

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## Theoretical Density

This is the density of a material calculated from the atomic weight and crystal structure. Where Nc = number of atoms in unit cell A = Atomic Weight [kg mol-1] Vc = Volume of unit cell [m3] NA = Avogadro’s number [atoms mol-1]

## Blaise Pascal [1623-1662]

French philosopher and mathematician whose many achievements include the invention of an adding machine and the development of the modern theory of probability. The first person to use a barometer to measure differences in altitude.

## Brake Mean Effective Pressure

This is the average effective cylinder pressure that does useful work calculated from the brake horse power. The work accomplished during one engine cycle divided by the engine swept volume. It is essentially the engine torque normalized by the engine displacement. The word ′brake′ denotes the actual torque/power available at the engine flywheel as measured

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## Pascal

The SI derived unit of pressure is the pascal or 1 newton per square metre. Conversions 1 bar = 1x105 Pa 1 standard atmosphere (atm) = 1.01325x105 Pa 1 lbf in-2 (psi) = 6894.76 Pa 1 tonf in-2 = 15.4443x106 Pa 1 torr = 1 mmHg 1 mmHg = 133.322 Pa 1 inHg =

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## A Weighting

This is the most generally used filter when making overall noise measurements. The attenuation of the sound signal with an A-weighted filter corresponds to the fact that the human ear is not as sensitive to sound of the lower frequencies as it is at the higher frequencies. The A-Weighted Sound Level is a single number

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