Or, before that, just send the dd process SIGINFO to get the same output printed once. `while :; do kill -INFO %1; sleep 1; done` if you want a "progress bar" of sorts.

As an aside: On BSDs (incl. macOS), SIGINFO is also able to be sent interactively by the line driver when you type ^T (like ^C sends SIGINT.) Kind of lame that Linux doesn't follow suit [or even have SIGINFO], or we'd see a lot more programs that build in useful "prod me for an update" hooks, the way they already have "prod me to reload my config" SIGHUP hooks.