Re: winter bee deaths - question
any cheap one will do, but a larger diaphragm with a plastic drum head on it is better for when they are in torpor and not really making much of a roar.
the best time to listen is when there is no wind or other background noise. by listening to all 4 sides of all of the boxes you can sometimes figure out at what level and/or what side they are on.
if it is warm enough for there to be a bee or two at the entrance it's ok to knock.
journaling the growth of a (mite) treatment free apiary started in 2010. 20+/- hives