Evidence for basal distortion-product otoacoustic emission components.
Distortion-product otoacoustic emissions (DPOAEs) were measured with traditional DP-grams and level/phase (L/P) maps in rabbits with either normal cochlear function or unique sound-induced cochlear losses that were characterized as either low-frequency or notched configurations. To demonstrate that emission generators distributed basal to the f(2) primary-tone contribute, in general, to DPOAE levels and phases, a high-frequency interference tone (IT) was presented at 1/3 of an octave (oct) above the f(2) primary-tone, and DPOAEs were re-measured as "augmented" DP-grams (ADP-grams) and L/P maps. The vector difference between the control and augmented functions was then computed to derive residual DP-grams (RDP-grams) and L/P maps. The resulting RDP-grams and L/P maps, which described the DPOAEs removed by the IT, supported the notion that basal DPOAE components routinely contribute to the generation of standard measures of DPOAEs. Separate experiments demonstrated that these components could not be attributed to the effects of the 1/3-oct IT on f(2), or DPOAEs generated by the addition of a third interfering tone. These basal components can "fill in" the lesion estimated by the commonly employed DP-gram. Thus, ADP-grams more accurately reveal the pattern of cochlear damage and may eventually lead to an improved DP-gram procedure.
Research Service, VA Loma Linda Healthcare System and Department of Otolaryngology-Head and Neck Surgery, Loma Linda University Medical Center, Loma Linda, California 92357, USA. glen.martin2@va.gov
Glen K
GK
Martin
Barden B
BB
Stagner
Brenda L
BL
Lonsbury-Martin
D000161:Acoustic Stimulation; D000818:Animals; D001299:Audiometry; D003051:Cochlea / Q000503:physiopathology*; D004195:Disease Models, Animal; D005260:Female; D006317:Hearing Loss, Noise-Induced / Q000503:physiopathology*; D008954:Models, Biological; D017084:Otoacoustic Emissions, Spontaneous; D011312:Pressure; D011817:Rabbits; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors