Gain in audio refers to the amount of amplification applied to a signal by any process that increases its strength. It is measured in decibels (dB) and is the ratio between the input volume and the output volume. Gain is a function of a sounds signal level within the circuit of an amplifier, which is the difference between the input level and output level. Gain is not the same as volume, which refers to the loudness of the sound. Gain is used to adjust the strength or voltage level of the signal, whether that be within the electrical components or in the digital realm. Gain comes into play at a few key points in the audio workflow, such as when using a microphone to record a singer or an instrument. Gain staging is the act of routing devices in series without adding noise-floor issues or unwanted distortion. Gain can be adjusted using a gain knob on a microphone preamp or other audio equipment.