Sensitivity is a simple setting on most detectors that allows you to adjust it up or down the degree to which it reacts to objects. When using the highest sensitivity settings, most detectors will sound chattery from all the mineralization in the ground. Sensitivity is the only control you have over how the detector reacts to mineralization.
Discrimination is a detector's ability to exclude certain objects, such as usually trash, to make it easier to find other items. Since most trashy targets ring up low, you can increase your discrimination to exclude many targets.
Discrimination tends to go hand-in-hand with notch discrimination. This feature allows you to notch out a specific target without turning the discrimination way up. Example: You may notch out pull-tabs while leaving everything that can be found both above and below those pull-tabs on the scale.
While slowly moving the coil back and forth over the target, you listen to tone pitch and volume. When pitch and/or volume is the highest, target will be directly under the center of
the search coil.
The threshold on a metal detector is a slight hum that you hear when the detector is on. This allows you hear breaks, which are targets that are discriminated.
This feature is used to adjust the detector for mineralization in the soil at the current location to be hunted. This must be done every time you change areas.
Not all detectors have this feature. Audio gain is used to adjust the volume on deeper targets.