  The Sun regularly produces large-scale eruptive events, such as coronal mass
ejections (CMEs) that can drive shock waves through the solar corona. Such
shocks can result in electron acceleration and subsequent radio emission in the
form of a type II radio burst. However, the early-phase evolution of shock
properties and its relationship to type II burst evolution is still subject to
investigation. Here we study the evolution of a CME-driven shock by comparing
three commonly used methods of calculating the Alfv\'en Mach number ($M_A$),
namely: shock geometry, a comparison of CME speed to a model of the coronal
Alfv\'en speed, and the type II band-splitting method. We applied the three
methods to the 2017 September 2 event, focusing on the shock wave observed in
extreme ultraviolet (EUV) by the Solar Ultraviolet Imager (SUVI) on board
GOES-16, in white-light by the Large Angle and Spectrometric Coronagraph
(LASCO) on board SOHO, and the type II radio burst observed by the Irish Low
Frequency Array (I-LOFAR). We show that the three different methods of
estimating shock $M_A$ yield consistent results and provide a means of relating
shock property evolution to the type II emission duration. The type II radio
emission emerged from near the nose of the CME when $M_A$ was in the range
1.4-2.4 at a heliocentric distance of $\sim$1.6 $R_\odot$. The emission ceased
when the CME nose reached $\sim$2.4 $R_\odot$, despite an increasing Alfv\'en
Mach number (up to 4). We suggest the radio emission cessation is due to the
lack of quasi-perpendicular geometry at this altitude, which inhibits efficient
electron acceleration and subsequent radio emission.
