Acoustics

  • Buildings
  • HVAC
  • Sound Spaces - Theatre, Auditorium and others
  • Acoustic Enclosures

Buildings

In homes and offices, sound insulation against air borne and impact sound is required and at times necessary to ensure comfort.

The noise in a room or hall may originate in 3 ways.

  • Air borne from a source within the room, e.g. typing office, weaving sheds, engine rooms.
  • Air borne from external sources.
  • By impact blows on the structure.

Noise in rooms can be reduced considerably by lining them with high quality sound absorbent material. Twiga Insul which combats reverberation most effectively is ideal for the purpose.

Structural cross connections or ties between the two partitions should either be avoided or the minimum number required should be used in order to cut mechanical linkage to a minimum.

(I) Partitions

When constructing double partitions using Twiga Insul, care should be taken to isolate the two leaves from each other at the edges by means of an absorbing material (say fiber felt). In short, the leaves must be fully “floating”.

The following are some of the recommended application methods.

  • Erect a staggered vertical framework of wooden battens (No cross supports)
  • Interweave Fiberglass Wool bypassing it in front of one batten and behind the next for the length of the partition.
  • Fix lining board only to the battens faced with insulation.
  • Painting, optional.

Note :

  • If a wooden frame has already been erected with cross battens in both vertical and horizontal positions, then strips of absorbing felt should be applied both horizontally and vertically on the battens before fixing the lining board to break the mechanical linkage.
  • The perforations in the lining board should preferably be on the side of noise source.

Method of application:

 

(II) Wall

  • Fix horizontal and/or vertical battens (Aluminium or GI Channels) to the walls at suitable centers.
  • Friction fill Fiberglass Tissue faced Fiberglass Wool of specified thickness and density between the grid.
  • Cover insulation with perforated lining board.

With Air Space

To further increase low frequency sound absorption use horizontal counter battening to provide an air space behind the insulation.

( III) Ceilings

An arrangement of GI Channels/Aluminium Channel system at suitable centers is used either suspended or fixed directly to the ceiling


HVAC

A. Duct Acoustic Lining

Duct Acoustic Lining

Insulation material for Duct Acoustic Lining shall be resin bonded Twiga Insul with one side factory laminated either black glass woven cloth or black glass tissue. The Thermal conductivity of Twiga Insul for air-conditioning application shall not exceed 0.034 W/m K at 25 deg C mean temperature and average Noise Reduction Coefficient (NRC=0.80, frequency range from100 Hz to 8000Hz).The density of Insul shall be either 32 Kg./m3 or 48 kg/m3 and the thickness shall not be less than 25mm.

The installation guideline for glass wool in Duct Acoustic Lining:

  • The inside duct surface should be cleaned with suitable solvents and rendered free from all physical and chemical impurities.
  • Fix 22 gauge G.I. channels & angle frame work 25mm wide x depth equal to thickness of Insul at 600mm centre, screwed to the sheet metal by means of brass metal screws.
  • Cut the panels of Insul & fix in framed work using two coats of cold applied bitumen/CPRX or any other equivalent approved product.
  • The inner most surface of Insul shall be covered with factory laminated either black glass woven cloth or black glass tissue.
  • Finally cover the Insul with 0.5 mm thick perforated aluminum sheet having 20% perforation with joints overlapped and screwed to the frame by means of brass metal screws, to produce an even surface.

B. AHU Room Insulation:

Plant rooms and AHU room walls and ceiling shall be provided with acoustic treatment to filter out the noise in such plant rooms and shall be provided with acoustic lining with TWIGA Insul -3000/50 suitably factory laminated with Twiga Black Glass Tissue.

The insulation should conform to non-combustibility, Class-P (not easily ignitable), Class 1(surface spread of flame NIL), and Class ‘O’ rating as per BS 476 standards.

Installation guideline:

  • The surface shall be cleaned and frame work of 22 gauge GI fabricated channels 25 mm x 50 mm screwed back to back at 60 cm centers shall be provided vertically and horizontally so that 60 x 60 cm squares are formed.
  • The gaps between frames shall be lined with a glass wool acoustic insulation with BGT as specified.
  • The entire surface shall then be covered with 24 gauge perforated aluminum sheet, 60 cm or 120 cm wide having at least 15 percent perforations, fixed with sheet metal screws.
  • Over-lapping of sheets shall be covered with aluminum beading. Acoustic lining of walls shall be terminated approximately 15 cm above the finished floor to prevent damage to insulation due to accidental water-logging in plant/AHU rooms.

Multiplex, Theatre, Auditorium, Studio and other Sound Spaces -

Twiga Insul is selected by nine out of ten sound spaces for its superior acoustic and thermal insulation properties. Twiga Insul is available in a wide range of densities, thicknesses, lengths and aesthetics.

Recommended Products –

Insul having density of 16 kg/m3 to 32 kg/m3 rolls / 40 kg/m3 to 64 kg/m3 boards can be used with either black glass tissue, white fiber glass tissue or black glass cloth facings and for ceiling, Insul Boards / Tiles with a density of 100 kg/m3 can be used to improve acoustics apart from being fire safe and easy to install.


Acoustic Enclosures

Twiga Insul is preferred for this application due to its following properties –

  • Resistance to vibration and jolting
  • Non corrosive.
  • Durable / Long life.
  • Vermin proof

Recommended Products –

Insul boards having density of 32 kg/m3 / 48 kg/m3 (50mm thick Black Glass Tissue faced) with thickness of 50 mm with NRC value of 0.96 and 1.21 respectively can be used for better sound absorption.

Option I

  • Clean the surfaces wherein insulation to be applied.
  • Apply a coat of cold setting adhesive CPRX compound or hot blown bitumen 85-25 grade and fix wooden battens or GI or Aluminium channels of height equal to the thickness of insulation to be used, 50mm for AHU and 100mm for D.G. Set rooms.
    Frame work to be spaced at 600 x 600mm C/C for the walls and ceiling.
  • Twiga Fiberglass in specified density and thickness is placed in position within the framework and covered with white or black non woven Fiberglass Tissue (FGT).
  • 24G perforated aluminium sheet with approx. 20-25% perforations is placed in position over the insulation and FGT with help of self tapping screws onto the framework.
  • Plain aluminium beading 25mm wide, 3mm thick is then placed at the joints of the perforated sheets and secured to the frame work by means of self tapping screws.
  • Acoustic lining of walls shall be terminated 150mm above the finished floor to prevent damage to insulation due to accidental water logging in plant or AHU rooms.

Note

Wherever wooden battens are used these shall be adequately treated against termite attack and painted with fire resistant paint. All metallic frames shall be treated with rust resistant primes.

Option II

  • Fix 50 x 50 x 150mm wooden pegs at interval of 1m x 0.6m x 0.6m with the help of screws..
  • Fix chicken wire mesh 12.5mm x 22 G of hexagonal construction over the pegs in order to create an air space of 50mm with the wall.
  • Fabricate and fix 0.63mm thick ‘Z’ type GI channels at intervals of 1m x0.6m C/C.
  • Fix Twiga Insul of required density and thickness over the pegs to the channel.
  • Spread a layer of Black non woven Fiberglass Tissue.
  • Fix aluminium or GI perforated sheet having at least 20-25% perforations with brass screws.
  • Fix aluminium beading 25mm x 3mm thick over joints with self tapping screws for the walls and roof area.

Note : All metallic frames shall be treated with rust resistant primes.