Equivalent input (also input-referred, referred-to-input (RTI), or input-related), is a method of referring to the signal or noise level at the output of a system as if it were due to an input to the same system. This input's value is called the Equivalent input. This is accomplished by removing all signal changes (e.g.
amplifier gain
Gain or GAIN may refer to:
Science and technology
* Gain (electronics), an electronics and signal processing term
* Antenna gain
* Gain (laser), the amplification involved in laser emission
* Gain (projection screens)
* Information gain in de ...
,
transducer sensitivity
Sensitivity may refer to:
Science and technology Natural sciences
* Sensitivity (physiology), the ability of an organism or organ to respond to external stimuli
** Sensory processing sensitivity in humans
* Sensitivity and specificity, statisti ...
, etc.) to get the units to match the input.
Examples
Equivalent input noise
A
microphone converts
acoustical energy to
electrical energy. Microphones have some level of electrical
noise at their output. This noise may have contributions from random
diaphragm
Diaphragm may refer to:
Anatomy
* Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen
* Pelvic diaphragm or pelvic floor, a pelvic structure
* Urogenital diaphragm or triangular ligament, a pelvic structure
Other
* Diap ...
movement,
thermal noise, or a dozen other sources, but those can all be thought of as an imaginary acoustic noise source injecting sound into the (now noiseless) microphone. The units on this noise are no longer
volts, but units of sound pressure (
pascal
Pascal, Pascal's or PASCAL may refer to:
People and fictional characters
* Pascal (given name), including a list of people with the name
* Pascal (surname), including a list of people and fictional characters with the name
** Blaise Pascal, Fren ...
s or
dBSPL), which can be directly compared to the desired sound pressure inputs. This is called ''equivalent input noise'' (EIN), or ''input-referred noise'' (IRN), or ''referred-to-input'' (RTI) ''noise''.
Input-related interference level
A device which uses a
microphone may be susceptible to
electromagnetic interference
Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electros ...
which causes
sonic artifacts. The problem is not in the microphone, but the interference level can be ''related'' back to the input to compare to the level of typical inputs to see how
audible the artifact is. This is called ''input-related interference level'' (IRIL).
References
Further reading
* (67 pages)
*
Acoustics
Noise (electronics)
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