The easiest “tell” when you’re trying to figure out if what you’re watching is a B-movie or something further down the action budget alphabet is in the effects.

How do the gunshots look and sound? How realistic is the bloody makeup? How convincing are the bullets to the head/skull explosions?

Lots of filmmakers know they can get their film financed if they line up a couple of B-list or lower stars, actors years past their peak popularity. But few are able to follow through and scrounge up good makeup and effects cash as well.

Heads burst and pistol barrels are pushed against craniums for a self-administered head-shots in “Black Noise,” a C-movie starring Alex Pettyfer (“Magic Mike,” the “Endless Love” remake) and Jackson Rathbone (“Twilight”). And the results are second-year-in-film-school bad.

The players make the best of this “Havana Syndrome” thriller about private commandos sent to save rich folks from an exclusive resort island where something or someone is putting deafening noises in their ears and triggering memories in their minds to gruesome effect.

Everybody in the five person “team” (Pettyfer, Rathbone, Eve Mauro, Wayne Gordon and Sadie Newman) is troubled and ripe for sonic attack and flashbacks to some earlier trauma.

It’s a good thing the island’s collection of rich folks who were the first assaulted seem to have been all but wiped out, as this C-Team Six Five is pretty wrapped-up in their own issues, start to finish.

Rathbone rolls out a Southern drawl as the team’s tech guy. Pettyfer and others put in the time to look like they know what they’re doing with firearms.

But there’s no urgency, no sense the narrative is propelling us forward and no real surprises as we watch the team endure shattering memories that mess with their heads and Our Hero tries to explode-the-heads of the terrorists/personal demons/aliens or whoever is pulling the strings.

With cardboard characters and lines like “No one is safe. No one,” it’s hard for anybody to work up much enthusiasm for their performances, relying on simple professionalism to carry the day. The script isn’t utter trash, but it’s close.

And then the post-production effects are layered in, and any effort made on set makes one hope that all involved at least got a nice paid working vacation to St. Kitts and St. Nevis out of it. From reading the trades, other actors were going to take some of these roles, and thought better of it.

Rating: R, graphic violence

Cast: Alex Pettyfer, Jackson Rathbone, Eve Mauro, Wayne Gordon and Sadie Newman

Credits: Directed by Philippe Martinez, scripted by Sean-Michael Argo, Philippe Martinez and Leigh Scott. A Saban Films release.

Running time: 1:26