Annoying, stressful and detrimental to health, the noise factor in our working environment – and even more so in the industrial environment – has to be taken into account right from the design phase onwards. Though some ambient noise comes from outside, most of the decibels the senses perceive are generally related to the business activity itself.

Good building means clear understanding of the sounds inherent in the operations conducted in the future building – whether it is an office building, an industrial site or a hospital, among many others. The well-insulated building entails tailor-made design which pinpoints solid-borne sound and vibration phenomena.

Interview with Olivier Pradines, Project Director, Industry, at GSE.

Is management of ambient noise now an integral part of building design?

O. P.: Yes, it has to be. The new acoustic standards which apply to recent construction, such as the NF EN 12354, NF EN 20140, NF EN ISO 140 for France, require increasing filtration of the noises and vibrations generated inside the buildings (chiller units, exhaust fans, air conditioning, elevators, piping...), and of those which come from outside – road and rail traffic, tramways, the industrial environment.

Each one of these noises has specific physical properties and techniques for treating them. This is why the type of noise and the type of noise propagation have to be identified prior to applying the right acoustic insulation solution in each new building.

Can you remind us what different sorts of noises we deal with on a daily basis?

O.P.: Every vibratory occurrence – voices, alarms ringing, engines running, doors slamming – sets the air vibrating and causes more or less intense vibrations which propagate in the air just like ripples on the surface of a lake when a stone is tossed into the water. Acoustics specialists distinguish between several different types of noise.

• Air-borne noise from outside the building (traffic, works) or inside (voices, radio…) which is diffused in the air.
• Solid-borne noise, our subject here. Unlike air-borne noise, solid-borne noise is propagated by the building itself and is caused by impacts against walls or floors – a chair scraping, a nail being driven into a wall, vibration from construction-related equipment … 
  In its construction projects, GSE increasingly emphasizes solutions to deal with the solid-borne noise from the technical installations involved in building operations and from industrial process equipment.

What are some of the solutions available to mitigate these infamous solid-borne noises?

O.P.: Both floors and ceilings and every element of the structure can be insulated helping to prevent noise. Several points must be taken into consideration: 

• In terms of the structure itself:
  - the foundations in contact with the ground,
  - the walls and the entresols in contact with the foundations;
   
• And in terms of what the structure holds:
  - interactions between the structure and the pipework,
  - effects to the structure from ventilation, elevators, machines…

Here are a few examples of solutions our suppliers propose today:

- Insulated building foundations: using simple springs, spring boxes, and anti-vibration mountings. This type of insulation is required when the superstructure (building or upper level of the building) has to be separated from the base it lays on. For the base can be subject to vibrations from outside sources such as roads and rail traffic. This can be a significant issue in urban environments.

- Insulation using viscoelastic dampers to protect buildings and machines: this requires installation of dampers, metallic pads and spring insulators on elastic bases. This applies to critical situations where, for example metro lines pass under the infrastructure or for areas subject to frequent earthquakes.  

- Insulating floating slabs or raft foundations: this consists in integrating spring boxes in the floor. This vibratory and acoustic insulation system is frequently used in buildings such as concert halls, discothèques, auditoriums, cinemas, restaurants, gyms, music schools and maintenance rooms.

- Suspension insulation of rotating machines: involves layers of appropriate suspension between the load-bearing structure and the rotating machine to provide vibratory insulation. There are 2 ranges:

• Elastomer suspensions of rotating machines adapted to suction fans, air-conditioners, electric pumps, motorcompressors, generator sets, AHU, chiller units … which provide vibratory attenuation greater than 90 % to 1500 rpm (25 Hz).
• Metallic range: very low frequency absorbers, up to 3 Hz, insulate from rotating machines at rotating speeds starting at 450 rpm, vibrators, impact machines, and provide attenuation of approximately 95 %.

- Insulating from elevator noise: this involves low frequency supports which provide for suspension and direction of the elevator cars.

- Insulation for piping: here, suspensions are laid between the load-bearing structure and the pipework to provide vibratory and acoustic isolation. These suspensions are used for the flanging and vibratory insulation of the piping used for fluids. These supports withstand temperatures between -70 °C and +300 °C.

- Ceiling suspensions: are placed between the load-bearing structure and the ceiling to improve vibro-acoustic attenuation. These absorbers are specially designed for suspended ceilings, air-conditioners and piping.

- Resilient bars: stop impact noise at the structural connections. Load-bearing and non-load-bearing walls, staircases, slabs…

How does one decide which type of acoustic insulation to use?

O.P.: If there are audible and annoying problems for the occupants of the building, acoustic insulation is necessary. Each building is unique and has its own set of characteristics. In complex cases, an engineering office is assigned to define the constructive principles to apply, and to design the structure.

In leading-edge industries, some production units use vibration means to test equipment – to test and asses for example, the resistance of products or equipment. In extreme cases, some vibrations can reach the levels found in fighter planes – a highly specific case but one that GSE has already encountered. These test facilities, which are part of the structure, were insulated by anti-vibration mountings as described above.