Equivalent input
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 is accomplished by removing all signal changes (e.g. amplifier gain, transducer sensitivity, etc.)The units on this noise are no longer volts, but units of sound pressure (pascals or dBSPL), which can be directly compared to the desired sound pressure inputs.A device which uses a microphone may be susceptible to electromagnetic interference 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.