IEC : International Electrotechnical Commission founded in 1906, the IEC is the world’s leading organization for the preparation and publication of International Standards for all electrical, electronic and related technologies. These are known collectively as "electrotechnology".
We include the IEC Definitions where appropriate in this Acoustic Glossary
The built-in electronic preamplifier transforms the high impedance charge output of the sensor into a low impedance voltage signal that can be transmitted over longer distances.This technique is widely used under other trade names: ICP ®, Deltatron ®, Piezotron ®, etc.
See also piezoelectric
See also real
Impedance Definition (IEC 801-25-13) at a given frequency, quotient of a dynamic field quantity (such as force, sound pressure) by a kinematic field quantity (such as vibration velocity, particle velocity), or quotient of a voltage by a current.
Note 1 : the term impedance is generally applied to a linear system and to steady sinusoidal signals.
Note 2 : in the case of a transient, impedance as a function of frequency is the quotient of the respective Fourier or Laplace transforms.
Note 3 : an impedance is the quotient of two quantities the product of which has the dimensions of power or power per unit area.
See also acoustic admittance • acoustic impedance • acoustic ohm • acoustic reactance • acoustic resistance • admittance • characteristic acoustic impedance • characteristic impedance of a medium • complex acoustic impedance • conjugate impedances • driving point impedance • specific acoustic impedance • specific acoustic reactance • specific acoustic resistance • specific wall admittance • specific wall impedance • transfer impedance • transmission impedance and radiation
Impulse in acoustics refers to events of short duration.
Impulse Definition (IEC 801-24-26) time integral of a force over the time during which the force is applied.
The frequency response, phase response, and transient response are all tied to this specification.
See also impulsive time weightings
See also direct sound
Inertance Definition (IEC 801-25-43) at a frequency for which inertia is dominant, quotient of sound pressure by the resulting in-phase volume acceleration during sinusoidal motion.
Note : inertance has dimensions of mass divided by the square of area
Initial Time Delay (ITD) the gap in time between the arrival of direct sound and the first sound reflected from a surface of the room to the listener.See also decay and reverberation.
See also particle acceleration
Instantaneous Particle Displacement Definition (IEC 801-21-25) in an elastic medium, vector whose extremity is the position of the particle at a given instant, and whose origin is at the equilibrium position of the particle.
See also particle displacement
Integrated Circuit Piezoelectric and Integrated Electronic Piezoelectric under IEPE.
Integration in mathematics an integral assigns numbers to functions in a way that can describe displacement, area, volume and other concepts that arise by combining data.
Integration in vibration, will convert an acceleration signal into a velocity signal, or a velocity signal into a displacement signal. For this reason, an accelerometer is the transducer of choice because velocity and displacement can be so easily derived from its output.
A vibration integrator is basically a low-pass filter with 6 dB or 12 dB per octave attenuation. Analogue integrators are only accurate over a discrete frequency range.See also differentiation
International Electrotechnical Commission (IEC) founded in 1906, the IEC is the world’s leading organization for the preparation and publication of International Standards for all electrical, electronic and related technologies. These are known collectively as "electrotechnology".
We include IEC Definitions where appropriate in this glossary
International System of Quantities : ISQ Definition (IEC 112-02-01) system of quantities based on the seven base quantities: length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity.
Note 1 : the International System of Quantities is published in the International Standard ISO/IEC 80000, Quantities and units.
Note 2 : the International System of Units (SI) is based on the ISQ.
For example at 16 metres from a point sound source the sound pressure level will be reduced by 20 log (16) = 24 dB, relative to the level at 1 metre, to check this example type 20 log (16) into Google.
Sound pressure level measurements are more common and they decrease by a factor of 2 every time the distances is doubled, in decibels this is 20·log (2) = 6 dB* for root power quantities. Strictly speaking this is not inverse square but inverse proportionality, also known as inverse distance law.* to check the above examples type 10 log (4) and 20 log (2) into Google.