To enjoy good acoustics a hall requires having, the correct geometry, accurate volume and proper surface covering with appropriate absorption materials. The aforementioned qualities are c1lawfied as passive acoustic properties. Passive acoustics are rarely adequate once the hall has been built if consideration has not been given to its acoustics during the design stage. It is a general rule, albeit misguided, that scant attention if any is given to the acoustic aspects during the early stage of the contract. The final result pertaining to the geometry and volume are usually therefore, irrevocable and are not consistent with good acoustic planning. The only course left thereafter is the treatment of surfaces. As an essential back up a speech reinforcement system has to be installed which adopts public address peripheries in the form of microphones and speakers.

The Main Hall at ITTHO conformed to no acoustic refinements during the design stage. As a consequence therefore, the hall had acoustics typical of many similar complexes throughout the world - it required acoustic treatment and the augmentation of a speech reinforcement system.

At this juncture although a modicum of improvements has been made, the problem has not been solved. The definition of the solution in this context is one which would qualify it as an auditorium capable of assuring that the entire audience capacity of some 500 people could hear the essentials, if not all of the content of a speech or a musical ensemble. However, a report by McNulty [1] for the Minster of Education, which is the result of 18 months of acoustic measurements, has been completed. The recommendations of this work have not yet been implemented. It is hoped that the exercise will be useful to technical and administrative personnel who are faced with the problem of commissioning new classrooms and auditoria. There is much refinement required when the reverberation time is high as is the case in ITTHO hall and similar auditoria. Consideration is given to this problem in [2] where the numbers of reflections are subscribed and the action needed to alleviate the distortion. Most studies deal with rectangular areas and indeed most auditoria have alcoves adjoining the hall. In a paper [3] this is simulated by computer for polygonal shaped enclosures. A recent paper shows how the measurement of reverberation time can be reduced to the measurement of the decay of sound in the enclosed area [4]. This would obviate some of the work, which has been carried out in this investigation. Indeed the hall was used for the verification of some of the test results. The aim therefore of this paper is to:

• Show the essentials of speech intelligibility test with specimen results
• highlight the effects of surface treatment
• provide the necessary information in a speech reinforcement system.