- The input admittance
*Y*(*x*) of a conical bore is more simply stated than its input impedance. For a conic section truncated at*x*=*x*_{0}, the input admittance is

where the pressure wave reflectance*C*^{-}/*C*^{+}is determined by the length of the bore and the boundary conditions at the opposite end, as discussed above. - Equation (13) applies equally well to bores of increasing and decreasing diameter by using either positive or negative values of
*x*. - Equation (13) may be interpreted as a parallel combination of an acoustic inertance and a term reminiscent of the impedance of a cylindrical waveguide (Benade, 1988).
- The impedance of the acoustic inertance, which has an equivalent acoustic mass
approaches infinity as
- The input admittance seen from the open end (at
*x*=-*L*) of a complete cone reduces to

where the pressure reflectance at the cone apex (*x*=0) is negative one. - An open end at
*x*= -*L*can be approximated by the low-frequency estimate - The resonance frequencies of a complete cone ideally open at its large end are thus found at the infinities of Eq. (14), which are given for
by

(15) - The complete cone with open mouth has a fundamental wavelength equal to two times its length and higher resonances that occur at all integer multiples of the fundamental frequency, as was observed for open-open cylindrical pipes.
- The anti-resonances of the complete cone, however, do not fall exactly midway between its resonances, but are influenced by the inertance term in Eq. (14).

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