parliamentary

Since 1991, Acoustic Directions has designed and commissioned sound systems for the House of Representatives, Senate and Great Hall that deliver loud, extremely intelligible, natural sounding voices, with excellent immunity from feedback.

In addition to high-intelligibility speech, our system for the Great Hall was required to support vocal and light rock music performances that are often presented in this room. The loudspeakers were designed in conjuction with the Parliament's architects, MGT Architects.

Each of our loudspeaker systems in Parliament house needed to overcome a challenging acoustic environment and accommodate strict architectural and physical constraints. Our solutions included the design of beam-steered line-array loudspeakers  driven by complex signal processing.

We also developed a semi-automatic  method to set up equalisation to minimise acoustic feedback for the large number of microphones in the House of Representatives and Senate.  This method calculates the equalisation based on a series of acoustic measurements of the open and closed loop gains of the system. This method was published in an AES Journal paper.

The public galleries of the House of Representatives had a strong flutter echo between their side walls, and this had the potential to degrade intelligibility of the poliiticians' speech when listeners in the gallery made a sound such as coughing. To rectify this, we specified an array of special acoustic diffusers for the walls, which diffused and directed sound into a 90 degree arc to retain the sound in the gallery. Conventional diffusers distribute sound into a 180 degree angle, and would direct the sound into the area where Members of Parliament sit.

The Legislative Assembly is the lower house of the New South Wales State Parliament. It is known as the "Bear Pit', due to the rather "robust" debating style that often occurs in this chamber. The chamber was built in 1842 and is heritage listed, and while this listing ensures its preservation for future generations, it had profound implications for the new loudspeaker system.

Acoustic Directions designed a loudspeaker system that provides a very high speech intelligibility whilst overcoming constraints of sight lines, a high ceiling and diverse audience areas. Special loudspeakers were designed by Acoustic Directions in conjunction with the NSW Government Architects, which met with the approval of the NSW Heritage Office.

For the main loudspeakers covering the politicians, we developed an innovative cardioid-Bessel array that produced excellent coverage free of the interference effects that usually plague multi-driver loudspeaker systems.

Although Bessel arrays have long been used to create wide dispersion, we believe our use of two Bessel arrays in a cardioid format is a world-first.

The aural result was most pleasing. The performance and intelligibility was as predicted, with the sound being very natural and intimate.