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SPA 3032 AcousticsTerms-gray

# SPA 3032 AcousticsTerms-gray - Acoustics Common Terms...

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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) = 10-3 usec (microsecond) = 10-6 sec or 10-3 msec Length km (kilometer = 103 m (meters) cm (centimeters) = 10-2 m mm (millimeter) = 10-3 m or 10-1 cm u or um (micron or micrometer) = 10-6 m or 10-3 mm Mass kg (kilogram = 103 g or 10-3 kg mg (milligram) = 10-3 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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