The strength of efferent activity predicted the amount of noise-induced hearing loss. A, Inverse correlation between the average efferent strength and the average DPOAE loss across guinea pig cochleas. Animals exhibiting larger efferent strengths showed less susceptibility to noise damage and had smaller DPOAE losses (r = 0.77; p < 0.0025; n = 11 ears). Gray triangles, gp 89L; filled square, gp 87L; the remainig ears are indicated by filled circles.B, Inverse correlation between average DPOAE threshold shifts and average efferent strength (r = 0.60;p < 0.02; n = 11 ears).Gray triangle, gp 89L; filled square, gp 87L; the remaining ears are indicated by open circles.