I have only been lucky enough to hear wolves howl once in the wild, on the edge of the Sierra de Culebra in Spain (I have also heard them from a zoo). While it is reasonably common to hear a wolf howling in the wild, seeing it happen is far rarer.
A wolf howl is an eerie sound, and certainly lives up to its claims of being spine tingling. I do not consider it an aggressive sound, and certainly it is not meant as one – wolves howl as a way to spread out, and avoid having to fight. In other words, howls are for other wolves and are not intended to scare humans.
Now, I fully understand that as a farmer these noises can be more alarming. However, it has been clearly shown that with relatively simple processes wolf predation can be reduced to near zero (large dogs to live with the sheep, and bringing the sheep near the farm house at night.
Wolf howls are very useful for wolf researchers as it allows them to document the animals without changing their behaviour by getting too close. European wolves tend to howl less than American wolves as there is more history of wolf hunting here. Still, these howls do occur in Europe, and as they recover these nocturnal noises will spread and become more common once again.
This wolf happened to howl right next to a camera trap, hence the footage. If you watch (or listen) right to the end, you can hear the pack answer. I know for most people the sound of wolves howling is thought to be scary (this is perpetuated by horror films), yet as this is essentially a long distance chat, or even there to stop violence, this fear should stop.