  Spectrum of coupled spin, acoustic, electro-dipole and electromagnetic waves
in orthorhombic perovskite multiferroics placed in external electric and
magnetic field has been calculated. Frequency and field dependencies of
electric, magnetic, and magnetoelectric susceptibilities of multiferroics with
cycloidal antiferromagnetic structure in external electric and magnetic fields
have been investigated as well. The spectrum of coupled waves has a band
structure. Width and frequency ranges of bands depend on external fields. The
possibility of control of electrodynamic properties of orthorhombic perovskite
multiferroics with cycloidal antiferromagnetic structure by external electric
and magnetic fields has been shown.
