**ICP ® Integrated Circuit Piezoelectric**, see IEPE below.

Throughout this Glossary we include IEC Definitions where appropriate

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

See also • various impulse definitions.

See also • impact sound pressure level (Li) • normalized impact sound pressure level (Ln & L'n)

The *impact hammer* has a transducer to measure the input force pulse while the response is typically measured using an accelerometer. The impact imparts a force pulse that excites the structure over a broad frequency range.

● 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

The frequency response, phase response, and transient response are all tied to this specification.

1 ) a single or multiple sound pressure peak(s) with a rise time less than 200 milliseconds or total duration less than 200 milliseconds.

2 ) or generally speaking, a noise which manifests itself as a succession of distinct pulses or transients.

See also • impulsive time weightings

See also • direct sound field

Incident Sound Wave

Indicators • LAeq,16h • Lday • Levening.

● Note :

See also other oscillation terms

See also • decay and reverberation.

See also instantaneous sound pressure

Instantaneous sound Intensity

Instantaneous Kinetic Sound Energy Density

See also • particle acceleration

See also • particle displacement

See also • particle velocity • peak particle velocity

Instantaneous Potential Sound Energy Density

Instantaneous Sound Energy Density

Instantaneous Sound Pressure

Instantaneous Speech Power

Institute of Acoustics

*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.

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* under IEC

*International System of Units* under SI units

*International Standards Organisation* under ISO

● 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.

Since the surface area of a sphere is 4·π·r^{2}, then the surface area **increases by a factor of 4** each time r (the distance from the source) is doubled

Measuring sound pressure levels is more common in the practical world and the sound pressure decreases by a factor of 2 every time the distances is doubled. In decibels this is 20·log (2) = 6 dB *. However we know that sound intensity ∝ p^{2} so the 'general' 6 dB rule still applies. Strictly speaking this is not *inverse square* but inverse proportionality, also known as inverse distance law.

See also • point source • line source • sound level calculations article

**Isotron ®** trade name for IEPE : integrated electronic piezoelectric.