Every hive I've opened would "increase their hum"
as a result of being smoked. In fact, this is
when you know that you have put enough smoke into
the entrance and under the inner cover.
One important point not mentioned in many books
is that one wants to "smoke", and then wait a bit.
The smoke itself is an irritant, but the intent is
to mask alarm pheromones. It takes some time for
the smoke to spread within the hive. If the bees
are busy fanning a crop, you will have one heck
of a time getting much smoke IN the entrance,
ditto if there is a good wind blowing. Keep at
it, the louder buzz is a good sign that you have
smoked "enough".
If you pay attention to sounds, and are in a quiet
area, you can hear a "Kamakaz-bee" flying at
a higher airspeed just seconds before she slams
face-first into your forehead or veil. This is
an easy message to translate - "back off, or be stung".
What is called for is more smoke at the entrance,
as it is my opinion that these Kamakaz-bees are
guards. I have no proof of this, but someday
I will take a hive, mark all the guards with
blue chalk, and try and see. Its hard to get a
good look at a bee that flies straight at you.
I'm not really worried about bees flying off
the comb, these are mostly house bees, and will
not be as defensive as the guards. Some folks
find it easier to pull a frame, and shake all
(or most) of the bees off before they do anything
else, shaking the frame over the top bars of
the hive, so that the bees retreat down into the
hive.
One very old trick is to use a pair of "hive
cloths" to cover all the top bars except the
one of current interest. This keeps nearly
100% of the bees "in the dark", and unable to
harass you. I use 'em on hives that are "grouchy"
and in need of requeening, and I provide them
in very apiary kit for every hired hand.