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Unformatted text preview: Acoustics  Common Terms
Frequency (1/period) Time (period) Pressure  dynes/cm2 Intensity  Watts/m2 Sinusoidal Complex Stimuli (Speech) Filtering Resonance Physical Principles
Length  meters Time  seconds or milliseconds (msec) Mass  kilograms Fundamental Physical Quantities System
MKS CGS Length
M(eter) C(entimeter Mass
K(ilogram) G(ram) Time
S(econd) S(econd) Fundamental Physical Quantities
Time msec (millisecond) = 103 usec (microsecond) = 106 sec or 103 msec Length km (kilometer = 103 m (meters) cm (centimeters) = 102 m mm (millimeter) = 103 m or 101 cm u or um (micron or micrometer) = 106 m or 103 mm Mass kg (kilogram = 103 g or 103 kg mg (milligram) = 103 g Derived Physical Quantities
Area  m2 Volume  m3 Velocity  m/sec speed  m/hr or m/sec Acceleration  m/sec2 Force  Newtons or dynes Pressure  pascals or bars or PSI Work  joules Power  watts Intensity  watts/m2 Definitions Displacement  movement of an object from one place to another. It has both magnitude and direction (vector quantity). Magnitude  maximum displacement on either side of equilibrium. Definitions Velocity  the rate at which the object's displacement is changing (vector). Speed  units of distance covered in one unit of time. S = d/t Acceleration  rate at which an object's velocity is changing (meters/sec2) Force
A push or pull when applied to a mass will cause acceleration. Gravity is a constant force Unit of measure of force is mass x acceleration (f = m x a) Force Newton = force required to move one kg with an acceleration of one meter/sec2 N = kg x m/sec2 (MKS metric system) Dyne = a much smaller force or that force required to move one gram with an acceleration of one cm/sec2 (d = g x cm/sec2) (cgs metric system) Pressure
A force spread over one unit of area Unit of pressure = Newton/meter2 (n/m2) Pascal (Pa) = 1N/m2 Or  we can refer to dynes/cm2 = microbar (a much smaller pressure) Or we can refer to pounds per square inch (PSI) Work Force x distance. Joule(j) = unit of work = force of one newton acting through a distance of one meter Power
Rate at which work is done. It can be measured in joules per second which is called watts. One watt = one joule of work per second. Acoustic Intensity Rate at which acoustic power passes through an area. Watts/m2 METRIC SYSTEMS Force
CGS MKS dyne Newton Sound Pressure
dynes/cm2 Newton/m2 SPL Reference
0.0002 dynes/cm2 20uPa ...
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 Spring '08
 Gerhardt

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