The acoustics of megabuilds

By Adam Fox

In the recent BBC documentary series, The Mayfair Hotel Megabuild, one of the issues encountered on the project was noise from the tube trains resonating through the building, particularly at basement levels. In this article, Adam Fox, whose company Mason UK featured in the documentary, explains why acoustics and vibration are a growing problem for many hotels in London and what can be done about it.

The recent BBC documentary series described the renovation of Claridge’s Hotel in London as the ‘‘most audacious hotel upgrade ever attempted.’’ For those involved in this project, it was a challenge and a privilege. However, from an acoustics point of view, the challenge we encountered here is one that many hotels across the capital face.

As part of the hotel upgrade, a new five story mega-basement was created. The documentary shows how during the construction process Norman McKibbin, construction director at the Maybourne Group, discovered that they could hear the hum of tube trains at basement level. As Claridge’s sits between three different underground lines, faint vibrations from the tracks two hundred meters away were carried through the ground and then amplified by the new basement structure. 

The basement was intended to include silent treatment rooms, where residents would receive massage therapy and enjoy a luxury spa. Ensuring that no noise disturbed this environment was therefore non-negotiable. Norman therefore hired a team of acoustics and vibration engineers, and that is where we entered the story.

Box in box solutions

The solution to the vibration problem was a box-in-box construction, which the Mayfair Hotel Megabuild described as a ‘‘room within a room.’’ Each inner room was surrounded by acoustic insulation and attached to the existing room with spring or rubber isolators that absorb the vibration and prevent the sound from travelling.

Although few projects can rival Claridge’s refurbishment for prestige, box-in-box constructions are commonly used for these purposes. The key component is a floating floor, the design of which is determined by the level of isolation required. A jack-up floating floor creates a floating concrete slab supported at regular intervals by either rubber or spring mounts, to create an air gap underneath. 

Walls can be isolated, either by being built on the floating floor or specially designed wall plates. The box-in-box structure is complete with an acoustic ceiling or lid. Acoustic ceilings are generally supported on drop rods on acoustics hangers, again rubber or springs are used.

Box-in-box constructions and the acoustic products they require are found in many types of building aside from hotels, including theatres, cinemas, and healthcare facilities. However, there is a growing demand for this type of solution as many developers and contractors require excavating basement levels. In London, this often brings the structure closer to the main source of vibration, underground tube tunnels. 

Getting the installation right requires experienced engineers and high-quality engineering products. On occasion, it will be necessary to provide bespoke products, to deal with additional challenges like space requirements that were not anticipated in a specification. Getting it right the first time is essential, as retrofitting a solution is prohibitively costly and can cause reputational damage, especially in a luxury development. 

Mason UK are specialists in vibration isolation for architectural noise control. To find out more about their recent projects, visit mason-uk.co.uk