PLANNING FOR GOOD ACOUSTICS

PLANNING FOR GOOD ACOUSTICSPlanning for good acoustics in a building begins with the selection of the building site and continues through all stages of designing. The architect will avoid inexcusable errors in design if he sets up a check, list of the necessary and sufficient measures to be taken for obtaining good acoustics.These steps, approximately in chronological order as follows:The selection of the site in the quietest surroundings consistent with other requirements.The making of a noise survey to determine how much sound insulation must be incorporated in a building to meet specified requirements of quietness.The arrangement of the rooms within the building.The selection of the proper sound insulation construction.The control of the noise within the building, including solid-borne as well as air-borne noise.The design of the size of each room that will insure the most advantageous flow of property diffused sound to all auditors, and that will enhance the aesthetic qualities of speech and music. The selection and distribution of the absorptive and reflective materials and constructions that will provide the optimum conditions for the growth, the decay, and the steady-mate distribution of sound in each room.The supervision of the installation of acoustical plaster, plastic absorbents, or other materials whose absorptivity is dependent on the manner of application.The installation of sound-amplification equipment under the supervision of a competent engineer; whenever such equipment is necessary.The inspection of the finished building including tests to determine whether the required sound insulation, sound absorption, and the other acoustical properties have been satisfactorily attained.Maintenance instructions, in writing, to be left with the building manager, indicatingHow the acoustical materials can be cleaned or redecorated?Which finishing in the building must be retained to maintain good acoustics?c. how, in large speech and music rooms where high quality reproduction is desired, the humidity should be maintained in order to avoid excessive absorption of high pitched sounds,d. How the sound amplification system should be maintained.REQUIREMENTS FOR GOOD ACOUSTICSIn designing for rooms intended for speaking purposes the prime objective is the realization of conditions that will provide good intelligibility of speech. This phrase, as used by telephone engineers, signifies how will speech is recognized and understood. In the design of music rooms the prime objective is most favorable enrichment of the total quality and tonal blending of the sounds.

It is necessary to provide not only the optimum conditions for listening to music but also the possible conditions for the rendition of music by skilled artists. When radio, violin, or any musical instrument is played in an enclosure is, in effect, a part of the instrument; that is, the instrument is coupled to a room, and the instrument excites the resonant frequencies of the room. A high-quality radio or a world-famous Stradivarius cannot produce high-quality music in a room that has poor acoustics.The above checklist is a practical aid to the fulfillment of the requisites for good acoustics. These requirements, which are applicable to all rooms used for speech and music, ma be stated as follows:

All noises, whether of outside or inside origin, should be reduced to levels that will not interfere with the hearing of speech or music.The rooms shape and size should be designed toGive a proper diffusion to the sound.Reinforce the sound reaching the audience, especially toward the rear seating area,Contribute to the attainment of a favorable ratio to direct to reflected sound for all auditors.Although these desirable conditions are also affected by the distribution of the absorptive materials and by the sound amplification system by the shape and size of the room. It is often necessary to design special wall and ceiling surfaces to act as reflectors fro the reinforcement of sound at the rear of the room, and it is sometimes essential to introduce splays or other surface irregularities to provide proper diffusion of sound.3. The reverberation time vs. frequency curve should approach the optimum characteristics, which are determined by the volume and type of room. The fluctuations in the growth and decay curves should be such as to yield optimum reverberation conditions.

4. Provision should be made for reinforcing the speech and music in a room so that sound level will be adequate in all parts of the room. In a small room, this requirement can be met by the proper design or reflective surfaces (walls, floors and ceilings); in a large room, in addition to the proper design of the reflective surfaces, a high-quality sound amplification system is indispensable.

In general, the above four requirements are necessary and sufficient for providing satisfactory acoustics in all rooms. In view of the differences between speech and music, the requirements stated above are not identical foe speech rooms and for music rooms. There are, however, certain broad features that apply to both: freedom from disturbing noise, proper shape ( a room shape that is good for music usually will be satisfactory also for speech ) and a sufficient sound level for all auditors.ENDprepared by:John Roman C. ToledanaBS-ARCHITECURE3C