The correct location of some of the world’s most valued artefacts is often a subject that invites thorny debate. However, wherever they are housed, the ancient treasures in museums around the world all require protection from potentially harmful sources of vibration. Here, Kyriakos Papanagiotou, founder and director of acoustics consultancy KP Acoustics, discusses the importance of getting an acoustics consultancy on board whenever construction work is taking place near a museum.
Controversy has surrounded the Parthenon Marbles since the beginning of the nineteenth century, when the British ambassador to the Ottoman Empire, Lord Elgin, spirited away some of the world’s finest sculptures from the Parthenon. The Parthenon Marbles (or Elgin Marbles as they are otherwise known) have resided in the British Museum in London since 1816.
According to reports, there is now the prospect of an agreement between Athens and London. The chairman of the British Museum, former Chancellor of the Exchequer George Osborne, is open to the possibility of returning the Parthenon Marbles to Greece. As Simon Jenkins recently wrote of the long running dispute,
As often in life, many of the most valuable things are delicate. That is certainly true of the splendours of ancient civilizations, whether they are on display in museums in Athens or London. One potential harm comes from vibration, which is why curators and conservators should consider working closely with an acoustics consultancy to eliminate the risks to their collections.
Sources of vibration
The most common source of vibration is of course footfall in the building, or visitor circulation. This ambient vibration, although rarely likely to cause major problems, is still worth monitoring. Studies have found that when coupled with certain floor types, the vibration generated by visitor circulation has the potential to reach levels that can cause damage to objects, especially those with pre-existing weaknesses.
In fact, one study of ambient vibration levels at the National Museum, the home of the Parthenon Marbles, demonstrated that ‘‘ambient vibration levels from visitors on wooden floors approach the damage levels identified and could cause pose a risk in some circumstances.’’ However, it is recommended the susceptibility of different floor types to vibration should be assessed on a case-by-case basis.
While there are many potential sources of vibration that need to be considered, vibration from demolition and construction activities is especially problematic and poses a higher risk. Whether the construction work is part of a renovation of the museum itself, or is taking place on an adjacent building, extreme care must be taken as construction activities generate vibration
Unfortunately for those facing this problem, there is generally a lack of reliable data on what levels of vibration objects can withstand. However, risks include objects ‘walking’ on smooth surfaces, where they might fall of the edge of a shelf or display unit. Other risks stem from the resonance of objects with natural frequencies similar to construction vibrations, and from the vibratory motion of objects that are very fragile or have existing weaknesses.
Whenever any construction work is involved, the first step is in planning and testing. During this stage, different tools and demolition or construction methods can be tested in different locations to assess which creates the least vibration. Testing can also help reveal whether a particular shelf design or pedestal shape and material are especially prone to amplify vibration. During this initial phase, a monitoring system is put in place. It is important to note that while testing and planning is key, it is quite likely that a construction project will produce unforeseen vibration and mitigation approaches will have to be adopted.
After the testing, mitigation strategies can be developed. For some objects that might mean isolators and dampeners to lessen the impact of vibration. It is preferable that, as far as is possible, displays and galleries are still open. With the correct acoustic treatment, this is often possible for many objects. However, in other instances it might be determined that it is safer to move the objects altogether. That doesn’t automatically mean moving them to a completely different location, but might instead meaning housing them in a different location in situ for the duration of the works.
Before any construction work begins, vibration trigger levels are established. Continual monitoring of vibration takes place, and if the agreed vibration levels are exceeded, it is important that construction work is brought to an abrupt halt. Most modern equipment will automatically alert users when a threshold level has been exceeded and for monitoring in museums, multiple accelerometers are usually deployed to ensure continuous and accurate measurements and data.
Curators might also consider the benefits of upskilling their staff to better prepare them for vibration monitoring. A range of studies have shown that successful projects usually involved effective communication and collaboration between contractors and museums staff, so ensuring that the latter have a solid grounding in vibration monitoring can have advantages that outlive any individual project. The KP Acoustics Research Labs are happy to offer courses to museum staff on precisely this sort of activity.
If the Parthenon Marbles are returned to the Acropolis, it will end over two centuries of disagreement about their ownership and location. However, even if disagreement persists, we should all agree that treasures such as these need to be carefully protected from sources of vibration.
KP Acoustics Group offers bespoke advice in acoustics, noise and vibration for a wide range of scenarios and industries across the world. To find out more, contact our team on +44 (0)20 8222 8778.