Distortion product otoacoustic emissions (DPOAEs) and transient-evoked OAEs (TEOAEs) assist in the evaluation of cochlear function. Negative middle-ear pressure is the most common dysfunction of the middle ear, which can result in hearing loss by diminishing the efficiency of energy transmission via the middle ear cavity. Because OAEs rely on transmission via the middle ear, OAE detection is diminished in the presence of deviant pressure in the ear canal or middle ear. The present study measured DPOAE levels in normal human ears upon voluntarily produced negative middle-ear pressure, and negative and positive ear canal pressures. The author's goal is to compare how negative middle-ear pressure, positive ear-canal pressure, and negative ear-canal pressure, all of the same magnitude, each affect the DPOAE response. Results indicate that positive ear-canal pressure and negative middle-pressure within each of the seven categorical ranges of pressure (e.g., -70 to -95 daPa) produce very similar effects on DPOAE amplitude, which is distinct from the effects of negative ear-canal pressure on the DPOAE amplitude. Specifically, positive ear-canal pressure and negative middle-ear pressure reduce DPOAE level at f2 frequencies from 600 to 1500 Hz, and at 3000 Hz; and increase DPOAE amplitude at 8000 Hz. The effects of applying negative ear-canal pressure have a relatively lesser effect. This suggests that compensating for the presence of middle-ear pressure has the benefit of increasing the ability to detect a DPOAE for frequencies below 2000 Hz and for 3000 Hz.