In electrical engineering and acoustics, immittance is a concept combining the
impedance and
admittance of a system or circuit. The term ''immittance'' was invented by
H. W. Bode.
[
]
It is sometimes convenient to use ''immittance'' to refer to a
complex number
In mathematics, a complex number is an element of a number system that extends the real numbers with a specific element denoted , called the imaginary unit and satisfying the equation i^= -1; every complex number can be expressed in the for ...
which may be either the impedance (ratio of
volt
The volt (symbol: V) is the unit of electric potential, electric potential difference ( voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827).
D ...
age to
current in electrical circuits, or
sound pressure
Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophon ...
to
volume velocity in acoustical systems) or the admittance (ratio of current to voltage, or volume velocity to sound pressure) of a system. In
audiology
Audiology (from Latin , "to hear"; and from Greek , '' -logia'') is a branch of science that studies hearing, balance, and related disorders. Audiologists treat those with hearing loss and proactively prevent related damage. By employing vario ...
,
tympanometry is sometimes called ''immittance testing''.
Immittance does not have units since it applies to both impedance and admittance, which have different units. However, in certain theoretical work it may be necessary to deal with general functions, which afterward will be specialised to become either an impedance or an admittance by the assignment of suitable units; in such cases it is convenient to refer to the functions as immittances.
In electronics, the "immittance"
Smith chart simply has both the impedance and admittance grids on the same chart, which is useful for cascading series-connected with parallel-connected electric circuits.
References
{{Refimprove, date=April 2007
Physical quantities
Electrical parameters