Total Coat Canada: Types of Noise Control Solutions

Types of Noise Control Solutions

Noise control solutions that result in a quiet and clear listening environment provide the most overall benefit in terms of improving the ability to hear conversations, music and cell phones within the vehicle. There are several basic ways of controlling noise. Usually an ideal solution to any problem can be obtained by applying a combination of: blocking the noise, absorbing it, damping the noise and isolating the noise source.

Barriers

Barriers are in essence a product that blocks sound. Some examples of barriers are: concrete blocks, bricks, drywall, plywood, sheet metal and loaded vinyl curtains. The ability of a material to block sound is measured as Transmission Loss (TL). As the frequency and density of the acoustic material increases, so does the TL. In essence, a denser material is a better barrier. Below are the TL measurements for some common materials used as sound barriers and how they compare to Total Coat:

Comparison of Transmission Loss (in dB) for different acoustical materials

	*Frequency (Hz)*
*Materials*	*125*	*250*	*500*	*1,000*	*2,000*	*4,000*	*8,000*
Lead
1/32" 2.0 lb./ft²	22	24	29	33	40	43	49
1/64" 1.0 lb./ft²	19	20	24	27	33	39	43
Plywood
3/4" 2.0 lb./ft²	24	22	27	28	25	27	35
1/4" 2.0 lb./ft²	17	15	20	24	28	27	25
Steel
18 ga. 2.0 lb./ft²	15	19	31	32	35	48	53
16 ga. 2.5 lb./ft²	21	30	34	37	40	47	52
Loaded Vinyl Sheet
0.5 lb./ft²	11	12	15	20	26	32	37
1.0 lb./ft²	15	17	21	28	33	37	43
Total Coat SC Premium*
1.0 mm	19	19	22	29	34	40	45
* Based on SAE J-1400 Test, applying 1mm thick coating of Sound Control Premium on Aluminum

Absorbers

Acoustical absorption materials are used as linings inside the enclosures where noise is generated. Whenever sound waves merge, the result is additive. In other words, a sound wave which bounces inside an enclosure such as an engine compartment will actually be louder (in dB) than the same engine in an open space. The purpose of these absorbers is to prevent the bouncing of these sound waves (reverberant noise). Due to the different lengths of sound waves, a material�s ability to absorb will depend on its thickness and density. Some common absorber materials used are fibreglass and polyurethane foam.

The sound wave energy is �absorbed� when it is transformed into heat energy. The sound wave impacts the surface of the material and it is �broken up� as it tries to move through the pores in foam or fibres in fibreglass.

Usually absorbers will have a facing (max. 2mm) to protect them from dust, oil, water and general abrasion & weathering. Unfortunately the facing will also reduce the performance of the absorption and add to the cost of the end product.

Damping Sheets & Tiles

Damping sheets & tiles are used to reduce the resonant vibration. For example an engine mounted on a base will vibrate (the enclosure it is in will also vibrate), thus resulting in resonant vibration, which causes structure-borne noise and airborne noise. The end result is an increase or prolonging of sound energy by reflection or vibration. Or in the case of a chute, bin or hopper, damping tries to reduce the �ringing� or �thunder� noise that results from the impact of materials that are �dropped in�. Damping materials in general do not wear very well and as such are not recommended for use in areas where there�s a lot of friction contact. In some cases it is possible to add a protective layer to the damping material, but this makes it more expensive.