  The design of structures that can yield efficient sound insulation
performance is a recurring topic in the acoustic engineering field. Special
attention is given to panels, which can be designed using several approaches to
achieve considerable sound attenuation. Previously, we have presented the
concept of thickness-varying periodic plates with optimized profiles to inhibit
flexural wave energy propagation. In this work, motivated by biological
structures that present multiple locally resonant elements able to cause
acoustic cloaking, we extend our shape optimization approach to design panels
that achieve improved acoustic insulation performance using either
thickness-varying profiles or locally resonant attachments. The optimization is
performed using numerical models that combine the Kirchhoff plate theory and
the plane wave expansion method. Our results indicate that panels based on
locally resonant mechanisms have the advantage of being robust against
variation in the incidence angle of acoustic excitation and, therefore, are
preferred for single-leaf applications.
