  We propose a new system suitable for studying analogue gravity effects,
consisting of a gas flowing in a duct with a compliant wall. Effective
transonic flows are obtained from uniform, low Mach number flows through the
reduction of the one-dimensional speed of sound induced by the wall compliance.
We show that the modified equation for linear perturbations can be written in a
Hamiltonian form. We perform a one-dimensional reduction consistent with the
canonical formulation, and deduce the analogue metric along with the first
dispersive term. In a weak dispersive regime, the spectrum emitted from a sonic
horizon is numerically shown to be Planckian, and with a temperature fixed by
the analogue surface gravity.
