GENERAL PRINCIPLES OF DESIGN

• When the problem of noise is an essential consideration in site selection. What survey must be made in advance?

  NOISE SURVEY
• Depending on the ambient noise level of the site, orientation, layout and structural design should be arranged to provide necessary noise reduction, so that the background noise level of not more than 40 to 45 dB (as measured on 'A' scale of sound level meter) is achieved within the hall.
• What determines the size of a theatre

  NUMBER OF AUDIENCE REQUIRED TO BE SEATED
• How many Sq.m is allocated per person which is used as a basis for calculating the floor area of the hall including gangways

  0.6 TO 0.9
• Consideration when determining the height of the hall

  VENTILATION, PRESENCE OF BALCONY, AND TYPE OF PERFORMANCE
• Average height for small halls

  6m
• Average height for large halls

  7.5m
• The volume per person required to be provided (size and shape)

  3.5m TO 5.5m
• Three classifications of existing halls(in terms of plan geometry)

  HORSESHOE-SHAPED PLAN, RECTANGULAR PLAN, AND FAN SHAPED PLAN
• The main acoustic parameter of enclosed spaces

  REVERBERATION TIME
• Have side walls that ensure short first reflection times, but the large parallel surfaces often result in acoustic defects, such as flutter echoes and standing waves.

  RECTANGULAR HALLS
• This shape of a hall makes it possible to accommodate a large audience while providing good visibility and acoustics

  FAN SHAPED PLAN
• The shape that prevents the formation of flutter echo by side walls, though the sound reflected from the rear wall can reach the front of the auditorium with a significant delay

  FAN SHAPED
• Plan shape of a hall that ensures good visibility, a sense of proximity to the sound source, and mutual eye contact between the spectators

  HORSE SHOE PLAN
• Not used for music performance

  FAN-SHAPED HALLS
• The one which is considered to give satisfactory results without introducing complications in the acoustical treatment of the hall

  FAN-SHAPED PLAN
• Maximum distance of the farthest seat from the curtain line, for the audience to discern the facial expressions of the performers

  23m
• Where the side walls are parallel, they may be left untreated to a length of about 7.5m from the proscenium end. (for side walls)
• What material must be used to treat a surface which likely to cause a delayed echo or flutter? (Side Walls)

  ABSORBING MATERIAL
• A shape that must be avoided for the ceiling of a theatre

  CONCAVE SHAPED CEILING
• What material must be used in the construction of the PORTION of the false ceiling near the proscenium to help the reflection from the stage to the audiences

  REFLECTIVE MATERIAL
• To control reverberation and partly prevent the build-up of audience noise, what material should be used to treat the rear portion of the ceiling?

  ABSORBING MATERIAL
• The elevation is based on the principle that each listener shall be elevated with respect to the person immediately in front of him so that the listener's head is about 12 cm above the path of sound, which would pass over the head of the person in front of him.

  ,
• The elevation of the balcony seat should be such that the line of sight is not inclined more than 30 degrees to the horizontal.
• How must seats be arranged?

  CONCENTRIC CIRCLE DRAWN FROM THE CENTER
• Minimum and maximum width of seats

  45 cm to 56 cm
• The distance of the front row works to about 3-6 m for drama and it should be 4.5 m or more for cinema purpose.
• A minimum distance of front seats should be determined by the highest point required to be seen on the stage, which is usually raised by about 75cm or more.
• The back-to-back distance of chairs in successive rows of seats shall be at least 85 cm.
• If extra comfort is required, higher spacing may be provided, which shall vary between 85cm and 106 cm. (Seats)