  Let $\alpha \in \mathbb{C}$ be an exponential period. We show that the real
and imaginary part of $\alpha$ are up to signs volumes of sets definable in the
o-minimal structure generated by $\mathbb{Q}$, the real exponential function
and ${\sin}|_{[0,1]}$. This is a weaker analogue of the precise
characterisation of ordinary periods as numbers whose real and imaginary part
are up to signs volumes of $\mathbb{Q}$-semi-algebraic sets. Furthermore, we
define a notion of naive exponential periods and compare it to the existing
notions using cohomological methods. This points to a relation between the
theory of periods and o-minimal structures.
