Many people take the view that managing vibration is more important than managing noise because excessive vibration can actually damage things while excessive noise is simply annoying.
We need to change this view.
Noise, not even excessive noise, can cause health problems for both humans and wildlife.
Fortunately, both scientists and operators are starting to understand this – even if our understanding of how this happens in still being developed.
Let’s start by understanding the differences between noise and vibration.
That’s easy – right? Vibration is what you feel and noise is what you hear – very simple.
Except that’s not strictly correct.
Both noise and vibration are pressure waves travelling through the air and/or the earth. Waves are described by their frequency, so some of these waves have audible frequencies (for humans roughly 20Hz to 20,000Hz) and some are sub-audible frequencies (less than 20Hz). We generally associate vibration with the sub-audible waves that travel through the ground. But what do we call these same waves that have component frequencies in the audible range? We will still probably “feel” them, but we will hear them too.
As an example, take a blast at a mine site. We normally think of the noise generated by the blast as coming from the explosive itself and the vibration as coming from the rock movement. But the movement of the rock at the face of the blast almost always has an audible component. So we can actually hear the movement of the rock as well as feel it.
What this means in a practical sense is that when we are concerned about the impact of an operation on either humans or wildlife, we need to measure both noise and vibration.
The impact of noise/vibration pollution on wildlife
For the rest of this article we will only look at the impact of noise/vibration pollution on wildlife simply because we all at least believe we have an “understanding” of the impact on humans.
It is important to start by saying that our knowledge about exactly how wildlife is impacted by noise and vibration is still developing – after all, it is more difficult to examine and interview wildlife!
Studies have been done on amphibians, arthropods, birds, fish, mammals, molluscs and reptiles. Results indicate that noise pollution not only impacts all of these groups, but also that their reactions to this pollution are very similar.
The first reaction is to attempt to avoid the noisy environment. However, this is not always possible.
Even where some species can move away, there are some very interesting consequences. For example, studies have shown that some noises can deter several seed-eating birds, thereby decreasing the spread of seeds. This in turn can lead to changes to the plant community in that area. In other words, noise pollution can even change plant communities!
Animals, like humans, use sound to communicate. Most species have developed distinctive calls to warn others of danger, attract mates, offspring identification, etc. Further, the different species within a given habitat occupy distinct sonic niches thereby allowing themselves to be heard above the general noise of other species and events. Human imposed noises (e.g. aircraft, construction, traffic, etc) can easily disrupt this balance.
Importantly, the hearing ranges of species differs significantly and is usually very different from human ranges. For example, bats and dolphins use frequencies above 20,000Hz while elephants use frequencies below 20Hz. Great apes seem to have a hearing range very similar to humans.
Ultimately however, it is very difficult to tell how sensitive an animal is to noise, but obviously the important point is to understand their hearing range.
As indicated above, some species try to avoid these noisy environments (leading to other problems as above), but some seem to adapt in other ways – e.g. by vocalising louder, or in different frequencies. But even these changes disrupt whole communities.
Some animals can neither move (or at least they are very reluctant to do so) nor change their vocalisations. Bats appear to fall into this category. So loud noises will often force bats to relocate even though this will impede their ability to access suitable feeding areas.
With the increasing military use of sonar type devices, seismic studies and increasing shipping volumes even our oceans have become very noisy. This is causing poorly understood changes to the lives not only of whales and dolphins, but also fish.
With humans, even noises that reach us while we sleep – even when we don’t wake up – set off the body’s acute stress response, in turn raising blood pressure and heart rate. We must at least assume that animals respond in a similar way.
Noise pollution is increasing
A point to think about – most forms of pollution are decreasing, but noise pollution is definitely increasing. We, as a society, will be forced to deal with this fact in the near future. On the positive side, noise pollution doesn’t build up like most other types of pollution do, so quick behavioural changes can have a big impact.
Texcel has been involved in a few of these studies over the years. The largest were a study of the impact of construction activities on the local bird and bat colonies in north-western WA and of cave dwelling bats in Central Qld.
As our knowledge in these areas improves, we can expect more and more legislation aimed at protecting our wildlife.