  An inclined gravity-driven soap film channel was used to study the wake
patterns formed behind a transversely oscillating cylinder at $Re =235 \pm 14$.
The natural frequency of vortex shedding from a stationary cylinder,
$f_{\text{St}}$, was used to identify the oscillation frequencies of interest.
The (dimensionless) frequency, $f^*=f/{f_{\text{St}}}$, and amplitude,
$A^*=A/D$, of the cylinder's motion was varied over a large portion of the
fundamental synchronization region (i.e., for $f^* \approx 1$), and a `map' of
wake patterns was constructed in ${(f^*, A^*)}$ space. Lock-on between the
frequency of the cylinder's motion and the dominant frequency of the resulting
vortex wake was observed for a large range of this parameter space,
predominantly manifested as synchronized `2S' and `2P' wake modes. Synchronized
`P+S', `2T', and `transitional' wakes were also found in smaller regions of
parameter space. Unsynchronized `coalescing' and `perturbed von~\karman' wakes
were observed as the oscillation frequency became sufficiently different from
$f_{\text_{St}}$. The wake patterns and vortex formation processes found in
this study, particularly for the 2P mode wakes, are more similar to those
observed by \cite{Williamson1988} in three-dimensional experiments than those
found by \cite{Leontini2006} in two-dimensional simulations, despite the
physical constraint from the soap film that prevents three-dimensional effects
in the wake.
