Finding sound solutions

PUBLISHED : Friday, 18 April, 2008, 12:00am
UPDATED : Friday, 18 April, 2008, 12:00am

Hong Kong is home to some wonderful feats of construction, but while the architecture is often marvelled at and the structural engineering applauded, few notice the work of the acoustic engineers.

A relative newcomer to the engineering industry, acoustic engineers or acoustic consultants assess the desired and undesired sounds as they affect a particular building, and try to find ways to enhance or reduce their impact. This may mean limiting external sounds such as traffic noise, or controlling reverberating internal noises such as those from building services plants.

Their ultimate goal is to create a comfortable acoustic environment that serves the function of the space.

'You see the architectural design and listen to the acoustic design,' said Sam Tsoi Pui-sang, a director of Arup in Hong Kong.

There are 12 acoustic consultants at Arup's headquarters in Kowloon Tong, and Mr Tsoi hopes to recruit more. 'Acoustic engineers have a systematic approach to their work. They start with the geometry and room envelope of the space, and determine how thick the walls need to be for sound insulation. By examining the interior spatial structure of a room, they must decide whether the walls should be curved or flat, whether the surfaces need to be reflective or absorbing, and how much noise the air-con grills should produce. Generally acoustic engineers don't tamper with the basic layout of the space unless they can foresee a big problem,' he said.

Local acoustic engineers are assigned to most large-scale building projects in Hong Kong, mainland China and Macau, whereas two decades ago they were unknown in the region. Previously they were not specialists but construction engineers without any acoustic training, and architects and designers often saw them as interfering with their rigid limitations on interior finishes, design and space. These days acoustic engineers are much more savvy.

In Hong Kong there is a shortage of highly trained personnel and unlike in the United States and Britain where degrees in acoustic engineering are offered, students here take acoustics as a module of their engineering or architectural degree.

'Trainees must also study the issues arising from environmental noise pollution. It is now standard practice for professionals in this field to undertake environmental noise assessment surveys and to ensure that the Environmental Protection Department's statutory guidelines on noise restrictions are observed,' Mr Tsoi said.

Aside from meeting environmental regulations, acoustic engineers have to find sound solutions that complement the plans of the architect, the requirements of the building services engineer, the vision of the interior designer and the needs of the client.

The sound solution should also meet the functional requirements of the project. For example, an opera house requires a very different sound treatment to a hotel lobby or a 10,000-seater outdoor stadium.

One such application was for the MTR Corporation. MTR employed Arup's acoustic consultants to improve the intelligibility of the spoken announcements in their station planning.

The consultants knew that speech intelligibility depended on the volume of the speakers, the level of the background noise and the room acoustics, so they did research at stations to determine the cause of the problem.

They soon found that the geometry of the concourse, platforms and the interior of the stations had many hard, reflective surfaces that caused sounds to reverberate. The acoustic consultants then worked out a way to create more absorptive surfaces without changing the look and feel of the station. As carpets were not appropriate and the design of the walls already fixed, they created false ceilings to cut down the reflection of the sounds and made the announcements intelligible.

'You have to think out of the box and outside your discipline and make your designs complement the visual design of the space,' said Mr Tsoi, whose team has worked on other high-profile construction projects including Langham Place Hotel in Mong Kok, the Guangdong Museum of Art in Guangzhou and the Macao Science Centre.

As the acoustic engineering profession matures in Hong Kong and the basic practices are standardised, some of the more routine work is being done by architects. This gives acoustic consultants the space to focus on more complex, high-risk projects.

'Increasingly clients want an integrated solution with sound, light and multimedia design in one space. This is exciting and more creative, but requires acoustic engineers to have a high level and broad base of knowledge of other aspects of design. Acoustic engineers should become acoustic designers, that is the way forward.'