Pressure in the middle ear changes along with changes in atmospheric pressure. The tympanic membrane will push inward if atmospheric pressure shifts in the positive direction, or outward if atmospheric pressure shifts in the negative direction. The resulting tympanic membrane distention is a result of a pressure differential across the plane of the tympanic membrane. The pressure differential directly impacts how energy conducts through the middle ear. Since otoacoustic emissions (OAEs) depend on efficient conduction via the middle ear, such pressure differentials influence the measurement of all types of OAEs, including spontaneous (SOAE), transient-evoked (TEOAE), and distortion-product (DPOAE) OAEs. This paper discusses the effect of changes in atmospheric pressure via a pressure chamber on the frequency and amplitude of SOAEs, TEOAEs and DPOAEs within normal-hearing adults. In general, changes in atmospheric pressure reduce the amplitude for all OAE types more in the low frequencies relative to high frequencies, and small changes in atmospheric pressure result in large amplitude reductions below 4 kHz. SOAEs appear to be the most sensitive to pressure changes in the 4 to 5 kHz region. Observed changes in the TEOAE spectrum to pressure variations suggest an increase in stiffness in middle-ear transduction upon the presence of a pressure differential across the tympanic membrane (TM). These results indicate that OAEs are sensitive to ambient pressure changes and as a result, lend credence to the practice of obtaining clinically useful OAE measurements when the pressure differential across the TM is near zero, i.e., at tympanic peak pressure (TPP). Currently, the Titan is the only commercially available OAE device capable of obtaining OAEs at TPP.