The ratio of the power output of an electroacoustic transducer, under specified conditions, to the power output of an ideal electroacoustic transducer.
Related Terms 
GEARBOXA system of gears which alter the ratio between the revolution of the engine and the propeller shaft so the propeller operates in a relatively efficient speed range. By using a gearbox the engine and the propeller shaft will revolve at different speeds. 
AMPLIFICATION

DIRECTIVITY FACTOR

FORM FACTOR

POISSON RATIO
The ratio of the transverse contracting strain to the elongation strain when a rod is stretched by forces which are applied at its ends and which are parallel to the rod's axis.

PLATE MODULUS
The ratio of the stress component Txx in an isotropic, elastic body obeying a generalized Hooke's law to the corresponding strain component Sxx, when the strain components Syy and Szz are 0; the sum of the Poisson ratio and twice the rigidity modulus.

PLANT FACTOR
The ratio of the average power load of an electric power plant to its rated capacity. Also known as capacity factor.

PHOTOELECTRIC CONSTANT
The ratio of the frequency of radiation causing emission of photoelectrons to the voltage corresponding to the energy absorbed by a photoelectron; equal to Planck's constant divided by the electron charge.

PHASE MARGIN
The difference between 180 and the phase of the loop ratio of a stable system at the gaincrossover frequency.

PERFORMANCE INDEX
The ratio of standard hours to the hours of work actually used; a ratio exceeding 1.00 (or 100) indicates subsoil and rocks in which the contained water is permanently frozen.
