We measure an effective temperature $T_{\rm eff.}$ in a turbulent flow, where $T_{\rm eff}$ is defined according to Cugliandolo \emph{et al.}, using a Fluctuation-Dissipation Relation (FDR). Although the hypothesis underlying the fluctuation-dissipation theorem does not strictly hold, we present experimental evidence that meaningful quantities can be extracted. $T_{\rm eff}$ is measured in a large Reynolds number turbulent air jet flow ($74000 \leq Re \leq 170000$), using the spectral fluctuations and response of a simple vibrating string. The wave-number spectra all collapse on a single master curve for all Reynolds numbers. This spectrum is in agreement with a very simple model derived from Kolmogorov's $1941$ theory, predicting a $k^{-11/3}$ scaling.