The Advanced ACTPol (AdvACT) upgrade to the Atacama Cosmology Telescope features large arrays of multichroic pixels consisting of two orthogonal-polarization pairs of superconducting bolometers at two observing frequency bands. We present measurements of the detector properties and noise data in a subset of a fielded multichroic array of AlMn transition-edge sensor (TES) detectors. In this array, the distribution of critical temperature Tc across detectors appears uniform at the percent level. The measured noise-equivalent power (NEP) distributions over ~ 1200 detectors are consistent with expectations. We find median NEPs of 4.0×10-17 √Hz for low-band detectors and 6.2×10-17√Hz for high-band detectors under covered-window telescope test conditions with optical loading comparable to observing with precipitable water vapor ~ 0.5 mm. Lastly, we show the estimated detector optical efficiency, and demonstrate the ability to perform optical characterization over hundreds of detectors at once using a cryogenic blackbody source.