Although most acoustic engineers know how to correctly select them, in many cases installers utilize acoustic hangers without taking into account several critical parameters.
In this article, we will describe the critical parameters to consider when selecting 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
This category is comprised of the following technical elements:
A.1.- Total weight of the suspended ceiling
This information is obtained by adding the weight of the different elements that will be installed. This information is given in units of kg/m2.
From an acoustic point of view, a lower amount of acoustic hangers, results in a lower transmission of structural borne noise.
therefore, it is important to know the maximum possible distance beween hangers allowed by the beams. 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 provided that the weight per square meter of 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 economic point of view, a correctly selected acoustic hanger can improve productivity and 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.
The figures below detail 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
Other than using less hangers in the system, it is possible to lower costs by using cheaper elastomer materials. For example, rubber materials are cheaper than spring materials. However, compared to springs, rubber materials have a higher natural frequency and therefore a lower degree of isolation.
Benefits of using correctly selected acoustic hangers
A correctly selected acoustic hanger improves on 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, with a Rw of 54 dB
The ceiling structure is as shown below. An important aspect to note is that the same tests were repeated using 1, 2 and 3 plaster boards.
As it can be seen in the graph bellow, the ceiling with acoustic hangers provides a gain on isolation ranging from 4 - 8 dB on the frequency span of 100 - 1000 Hz.
The table below shows the Rw values on ceilings with multiple plasterboards.
As shown in the table, The Rw value obtained for a ceiling using 1 plasterboard + acoustic hanger is quivalent to 3 plasterboards + rigid suspension.
Official laboratory tests can be downloaded from the link below:
http://www.akustik.com/en-GB/laboratory-tests/
The same type of test was done on wooden ceilings, measuring impact noise and airborne noise.
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 shown from the two graphs, 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 being effectively installed quickly, saving customers time and money.
United Kingdom
