Thanks. I googled HDAPM and it seems that there's a lot of issues related to 7200rpm HDDs and this clicking/beeping noise.
Does anyone know if there any disadvantages to using this program? One disadvantage I found: forcing the drive heads to park less may reduce noise but it seems it can also raise the temperature of the HD, which can't be good for HD reliability:
https://forums.macrumors.com/posts/8915199/ And since the drive heads park less, it consumes more battery life (
https://forums.macrumors.com/posts/7326977/ ).
Also, the readme for that program states, there are instances where you may wish the drive heads to park more, but I don't know enough about this stuff to understand what instances those would be, which makes me wonder if I should mess around with the drive's behavior with this program.
Now I'm not so sure if I want to get a 7200rpm HDD for my future MBP purchase. If you you google "HDAPM" or search this forum, this issue appears common to many 7200rpm drives in Apple laptops. It goes back to at least 2008 (
https://forums.macrumors.com/posts/5094464/ ) and judging by the post above, it hasn't been addressed yet.