ACOUSTICAL DESIGN CONSIDERATIONS

ACOUSTICAL DESIGN CONSIDERATIONSSANIYYA MUJEEB S8 ROLL NO:27ROOM ACOUSTICAL ATTRIBUTES AFFECTING THE QUALITY OF MUSIC

The shape and volume of the room, its audience capacity and attendance and surface acoustical treatments all contribute to certain room-acoustical characteristicsIn the music gives the impression of being performed in a small intimate hall, the auditorium is said to have acoustical intimacy ie The initial time delay gap ie the time delay gap between the sound received by a listener and the first reflection from any bounding surface of the room is shorter than 20 msec ,the direct is not too faint and the room is found to be acoustically intimate.Acoustical intimacy is one of the most desirable features of an auditorium used primarily for music.Another important room-acoustic feature of a hall used for music is balance. It can be achieved by numerous sound-reflective and sound-diffusive surfaces around the sound source to strengthen and improve the balance between various sections of the orchestra as well as between the orchestra and soloists. If the musical sounds are well mixed before they reach the listener, so that they are perceived as harmonious ,the sending end of the auditorium is said to have good blend.The reflective and diffusive orchestra enclosures control blend. If an orchestra platform or orchestra pit is too wide, it will lack a good blendIf the musicians and soloists have the ability to perform in unison so that the entire orchestra sounds like a well-rehearsed and coordinated unit, the music hall is said to possess ensemble.Ensemble can be enhanced by a well proportioned and suitably raked stage floor and by stage enclosures that project the sound from one side of the platform to the otherFreedom from noise, ie the reduction of exterior and interior noises to inaudibility or at least an acceptable minimum, is one of the most important requisites in auditoriums for musicAnother essential room acoustic quality is the complete freedom from acoustical defects such as echo, sound concentration , distortion and sound shadow

ROOM FOR MUSICEFFECTS OF ROOM ACOUSTICS ON MUSICRoom acoustical attribute exercises a marked influence on the various stages of musical process, that is -on composition-on performance (production)-on listeningSince the appreciation of music cannot be dissociated from the acoustical environment of the room in which it is performed, musicians normally adjust their performance according to the acoustic quality of the room in which they are playing

Sound isolation and background noise are the important acoustic considerations in the music department.The shape and volume of the room, its audience capacity and attendance, and surface and acoustical treatments all contribute to the room-acoustical characteristics which affect the sound quality of music performed in the hallAcoustical considerations in the architectural design of music auditoriumsNo music hall is built for one specific type or style of music.Thus a carefully controlled RT will increase fullness of tone and will help loudness, definition and diffusion. However an ideal RT is only a contributing factor for good performanceDefinition will be satisfactory if the initial time -delay gap do not exceed 20msec ; if the direct sound is loud enough relative to the reverberant sound ,then the listeners are close to the sound source ; that is there is no echoProviding an adequate supply and distribution of bass tones over a large audience area (above 2500 seats) is an acoustical problem as the fundamentals of several musical instruments (double bass, harp etc.) are relatively weak To achieve uniform quality of sound over the entire area, balconies should not protrude too deeply into the air space of the room.Listeners should have unobstructed sight lines so that they receive ample direct sound Room should be of reasonable size and proportion and concave enclosures should be avoidedIn order to avoid echo, we need to provide longer RT and adequate diffusion. The frequencies of sound in the acoustics of music halls extend over arrange of 30 Hz to 12000 HzAttention should be taken to control noise and vibrations coming from heating, ventilating and air-conditioning systems, electrical and mechanical rooms and from surface and undergroundMasking noise should be reduced to an absolute minimum to avoid interference with pianissimo notesFLOOR SHAPESThe shape of the floor in a room for music affects the sound source transmission path receiver sequenceRectangular shapeCross reflection between parallel walls contribute to increased fullness of tone, a highly desirable feature for music hallsHorse shoe shapeTraditional layout of Opera housesCharacteristic feature is the rings of boxes on top of each other. Even without interior sound absorptive treatments, they contribute to efficient sound absorptionCurvilinear Floor shapeNormally associated with a dome roof of excessive height.Unless treated acoustically, they may create echoes, long-delayed reflections and sound concentrations. So, curvilinear floors should be avoided.

Irregular Floor shapeIt can bring the audience unusually close to sound source and cause random distribution of absorbent elements and diffusive surface irregularities. The free relationship between audience and performance area offers wide scope in design and fulfillment of several acoustical requirementsCONCERT HALLSThe audience and musicians are contained within the same space with no separating structure between themThere is no specific room shapeThe use of balconies in large concert halls is advantageous as it brings the audience closer to the platformAchievement of highly desirable long RT in concert halls in difficultIn a concert hall with volume less than 90000cu ft., the use of sound amplification system should be avoidedWhile designing an orchestra platform:Floor area should be based on the space requirements of musicians and their instrumentsClose musician-listener relationship should be achieved with horizontal and vertical sight clearance to provide loudness , intimacy and definitionThe orchestra platform should be neither too deep nor too wide. A maximum depth of 9m and a minimum width of 18m is recommendedThe surrounding enclosures must have reflective treatments to reduce undesirable sound absorptionThe level of the platform must be elevated high enough above the audience floor level to provide ample direct sound to every listenerStructural, mechanical and electrical requirements should be coordinated with acoustical needsOPERA HOUSESA combination of a legitimate theatre and a concert hallOpera houses uses proscenium stages with the separation between performers and spectatorsThe area and volume should be adjustable to suit orchestras of different sizes and to secure balance within the orchestraIn the relationship between the audience area and stage house, coupled spaces should be eliminated. Provision for an apron stage protruding into the audience is recommended to reduce distance between singer and audienceBIBLIOGRAPHY

Reference from the book:Architectural Acoustics and Noise Control-theory design and practiceBy S.Kandaswamy