Fig. 2.

Intensities of second (2f₀) and third (3f₀) harmonics in emitted, tracheal, and ICAS signals, relative to that of the fundamental frequency (f₀). Symbols indicate means (with ranges specified by vertical lines), calculated from 20 recordings, except for the two cases in which <20 recordings were available (see Table 1). Identical symbols indicate that measurements are from concurrent recordings. Horizontal dashed lines indicate means per anatomical compartment, calculated from the mean values of individual birds. The values of these means are indicated through arrows on the vertical axis. Circle, CD1; square, CD2; diamond, RD1; horizontal hourglass, RD2; hourglass, RD2; triangle, RD3; inverted triangle, RD4.