Although most acoustic engineers know how to make a correct selection of them, in many cases installers use and install the acoustic hangers without taking into account several critical parameters.
On the present article, we will describe what are the critical parameters to take into account when making a selection of an acoustic hanger.
We can distinguish 3 different categories for these parameters:
- A. Technical parameters
- B. Installation parameters
- C. Economic parameters
At the end of this report, we will demonstrate the technical benefits of using acoustic hangers on impact noise and airborne tests in concrete and wooden buildings.
A.- Technical parameters
In this category we must know the following technical elements:
A.1.- Total weight of the suspended ceiling
This information is obtained adding the weight of the different elements that will be installed. This information is given on a kg/m2 unit.
From an acoustic point of view, the lower is the amount of acoustic hangers, the lower are the points of transmission of structural borne noise.
The key question here is to know the maximum distance that the beams used allow us. In fact, there is a wide range of profiles or beams that are produced in the market. Those profiles that allow us to use a lower quantity of acoustic hangers are the ones that we will favour.
- Ceiling 1: A = 1 m (3,28ft) B = 0.6 m (1,97ft) Surface supported per acoustic hanger = 0.6 m² (6.46ft²)
- Ceiling 2: A = 1.5 m (4.92ft) B = 0.6 m (1,97ft) (1,97ft) Surface supported per acoustic hanger = 0.9 m² (9.69ft²)
A.3.- Load per acoustic hanger
The load per acoustic hanger is obtained from the following formula:
Weight of suspended ceiling x surface covered by each acoustic hanger
If we follow the previous example providing that the weight per ceiling is 40 kg/m² (8.19 lbs/ft²), here are the results:
- Ceiling 1 = 40kg/m² x 0,6 m² = 24kg (8,19lbs/ft² x 6,46ft² = 52,91lbs)
- Ceiling 2 = 40kg/m² x 0,9 m² = 36kg (8,19lbs/ft² x 9,69ft² = 79,36lbs)
Ceiling 1 = 11 Hz Natural frequency
Ceiling 2 = 8 Hz Natural frequency
As it can be seen in this case, a ceiling with lower amount of acoustic hangers does not only decrease the natural frequency, but also decreases the number of points where there is a transmission of vibration.
B.- Installation parameters
From a technical and from an economic point of view, a correctly selected acoustic hanger can improve the productivity and the acoustic insulation degree.
B.1.- Adapting the acoustic hanger to the type of beam
There is a wide variety of acoustic hangers. Some of them are specifically designed to adapt to a specific type of beam.
On the following lines we will describe which hanger fits each type of beam.
60-27 type profile » Akustik Super T-60
Universal system for concrete ceilings » Akustik 4
"I" profile » Grand Akustik 3
47 type profile » Akustik T-47
Universal system for wooden construction » Akustik Side
Universal system for Saw beams » Akustik Saw
B.2.- Metric diameter
Some ceiling structures require M-6 rods but in other cases M-8 or even M-12 are required.
Akustik + Sylomer acoustic hangers are available in M-6.
Akustik + mecanocaucho hangers are available in M-6, M-8, M-12 and M-14.
C.- Economic parameters
Apart from the fact of using less hangers on the system, there is a possibility to obtain lower prices using elastomer materials that have a lower cost. For example, materials in rubber can reduce the costs. The trade off is that the natural frequency that can be achieved is higher, therefore the degree of isolation is also lower.
Benefits of using correctly selected acoustic hangers
A correctly selected acoustic hanger improves on a great manner the isolation of airborne and impact noise
Comparative tests on concrete buildings
The aim of this test was to compare the airborne noise isolation on a ceiling using Akustik + Sylomer acoustic hangers Vs a ceiling using rigid suspension (M6 rod).
The slab used was a ceramic hollow block. Very popular in European building techniques, which gives a Rw of 54 dB
The ceiling structure is as shown below. Important aspect to remark is that the same tests were repeated using 1, 2 and 3 plaster boards.
As it can be seen on the graphic 1, the ceiling with acoustic hangers is providing a gain on isolation ranging from 4 - 8 dB on the frequency span of 100 - 1000 Hz.
The table bellow shows the Rw values on ceilings with multiple plasterboards.
As it can be seen, The Rw value obtained with a ceiling using 1 plasterboard + acoustic hanger equals to 3 plasterboards + rigid suspension.
Official laboratory tests can be downloaded on the link below:
http://www.akustik.com/en-GB/laboratory-tests/
The same type of test was done on wooden ceilings. In this case, impact noise was also measured.
Impact noise test on wooden building.
Link to official lab test results:
http://www.akustik.com/download/ensayos/ift_arena_impacto_original.pdf
Airborne noise test on wooden ceiling
Official lab test results can be downloaded here:
http://www.akustik.com/download/ensayos/ift_arena_aereo_original.pdf
As it can be seen, great improvements can be achieved without adding much weight to already existing wooden structures.
Conclusion:
Acoustic hangers that have been correctly selected can provide great acoustic improvements without adding much cost and weight to existing concrete or wooden structures.
Correctly selected acoustic hangers are capable of providing quick installation procedures to the installers, allowing them to save time and money.
United Kingdom
