Kuala Lumpur's Latest Place of Worship Sets New Audio Standards
Longthrow Mosque

Pro Sound News Asia      December 1999
by Graeme Nesbitt

MALAYSIA - The national architectural icon and unabashed symbol of the country's growth and 'can do' attitude is the Petronas Twin Towers, currently the world's tallest building. Like the Sydney Opera House, the Eiffel Tower and the Empire State building it personifies the aspirations and identity of the nation at the time of construction. Arguably more impressive, but with restrained reverential ebullience are the mosques, the place of worship for the majority Muslim populace.

The latest mosque to be constructed, is the Putra Mosque. Soon to be officially opened, it is the central landmark of the new city of Putrajaya, which will be the country's future Government and administrative centre, and is located adjacent to the Prime Minister's new office and department.

The sound system was designed by Perunding HTA Son Bhd, a consultant company which specialises in acoustics, vibration, industrial noise and electroacoustics. Director Ir Joseph L Tai explains that the brief from the client - Putrajaya and project manager KLCC, the company which manages the Twin Towers complex - was high quality performance from the sound system.

"The criteria we felt that really needed specification were the reverberation time (RT60), the ambient noise rating level (NR) and the absence of acoustic defects such as echo, and uneven sound distribution," he explains.

For the main prayer hall, accommodating over 8,000, Ir Tai and fellow director Eddie Ng set a 2.0 second reverberation time (acceptable for religious buildings) with NR45 for ambience.

Because specialist mosque sound design has not been widely practised, there are almost no examples of 'good sounding' mosques. Many still have on-going acoustic problems. Ng contacted AES standards committee head Dan Queen, to find there were no international standards for mosque sound systems, so they based the design on industry standards,

For part of the design process, Perunding HTA Son Bind used computer analysis techniques to establish, predict and improve the acoustics of the Putra Mosque. These modern, analysis methods enabled precise solutions to be adopted. As a result, less acoustic materials were installed. It enabled the maximum use of traditional interior finishings such as stained glass, marble, and plaster, so the beauty of traditional architecture was not sacrificed for better sound.

From the computer simulation, Perunding HTA was able to chart out sound reflections that return to a listener, and predict their paths, points of incidences, delay time, amplification, and other variables.

The main physical factor responsible for acoustics was the dome. Its underside diameter of approximately 45 metres and apex height of 60 metres resembled a huge focussing bowl. It was also responsible for echo effects that severely impair sound intelligibility. Computer analyses established the fact that most early (strong) reflections were from the dome.

To treat the dome acoustically without revealing soft material texture, special rigid fibreglass panels were used. They appear to be smooth hard plaster from a distance, but they actually have microporous holes on the surface for sound absorption. The panels were cut meticulously into small shapes to fit in spaces between the patterned mouldings of the dome. Other surfaces where similar panels were installed were restricted to the upper side walls and underside of galleries.

The carpet on the floor was acoustically specified to give it an additional role as an effective acoustic measure. For the project, Perunding was able to source a 50% local supply of acoustic materials and labour was 100% Malaysian.

The sound system was designed in a strategic manner to support good acoustics, apart from its fundamental requisite to reproduce excellent sound. Sound trajectories were controlled in terms of directivity factor and dispersion angles. The key was to have all reflected sounds to a listener constraint to within 50m.

A unique special feature was added in the sound system design. "We took the innovative approach of using front throw speakers to create the effect of all sounds originating from the direction of the imam (prayer leader)," says Ng

This approach lends directionality that is fundamental to the architectural and body positioning in Muslim worship, where everything points to Makka (Mecca).

A special high quality loudspeaker was required to deliver all the desired frequencies intact, over a huge 40 metre throw. The frequency range was desired at 40 Hz to 16 kHz to cover both female and male trained and untrained vocals.

"For state-of-the-art purposes", adds Ng, "we sought a fully digital processing system and self powered loudspeakers."

The benefits of a digital system include components such as equalisers, delay units and compressor/limiters. The system is not only intelligent but also space saving It has all the IT abilities to transmit and receive electronic sermons, provide continuous condition monitoring and facilitate online repair and maintenance.

Eventually a Meyer sound system was selected for the challenge. Meyer has a strong reputation as a leading high performance equipment supplier worldwide. Upon testing and commissioning Perunding found all design criteria satisfied its original brief. Reverberation time was below 2.0 seconds (1.9 seconds), sound uniformity within +/-3 d13 and ambient noise rating level below NR50 (NR45).

The imam at the Putra Mosque was originally given a wireless microphone for the occasions he passes it around to accessible worshippers. This produced some cancellation effects which were not detected, but which worshippers understanding Arabic commented on during the tests. Now the imam, who faces the wall towards Mecca in the same direction as the congregation, uses Al C647E and Sennheiser ES 845 mics

"The entire team of architects, engineering consultants and the main contractor, Saudi Bin Ladin, together with specialist subcontractor Integrated Audio Visual Sdn Bhd, put in maximum effort and co-operation in seeing this achievement through," concludes Ir Tai.

With another mosque planned for neighbouring Cyberjaya, where the Multimedia University is located, together with the growing numbers of Muslims worldwide, the Malaysian team could well find itself in demand as a specialist for mosque installations.