Levels of Response are ordered from the simplest to the most complex. The levels that are used in the FHI are representative of the generally agreed-upon developmental progression of use of hearing.

Typically, individuals (including infants, children, and adults) who are awake use their hearing in a manner that can be observed and reported in one of these 6 categories. A typical hearer fluctuates between levels of response and chooses which sound sources to respond to, even when there are multiple, competing sound sources. A typical hearer is able to quickly localize, discriminate, then recognize or comprehend the sound that is selected for response.