General procedure for tuning a notch filter is to use a single band of parametric EQ. That requires setting three variables: frequency center, filter Q (essentially the bandwith of the filter, equating to how aggressively pointy or smooth and flat the curve is), and gain. Start by dialing in the approximate 16kHz frequency center, set Q to something like 5 or so, boost gain, and determine if that aggravates the problem, making it worse (checking by ear or visually). Fine tune the frequency center to home in precisely on the frequency of the problematic noise line. Boosting helps do this because it further excites the unwanted signal. Fine-tune the frequency setting until the noise is loudest (or brightest). When precisely tuned, the unwanted signal will remain emphasized even a very high Q filter setting. Now change gain to cut instead of boost. The filter is now attenuating the problematic frequency range. Further adjust Q to make the notch just wide enough to cover the bandwidth of the unwanted signal, without effecting the region below and above.
As always, listen carefully to what the filter is doing specifically, but also listen to everything else with a broader ear. It may sound best to only partly attenuate the noise signal instead of trying to remove it entirely. Make sure the cure isn't introducing unwanted problems itself. Often less is more, but it takes careful listening to be sure.
[edited for typos and clarity]