Soundproofing - How good is Insulflex ?

INSULFLEX was designed as a heat/cold insulating material (thermal insulation)...and NEVER for acoustic control/soundproofing purposes. It's mostly used in the air-conditioning and other similar industries that require thermal insulation. In the US, Ensolite is also similar to Insulfex and its primarily a thermal insulating material.

In Malaysia, certain parties had easy access to this material a long time ago, and started promoting it to car audio shops as being a suitable "soundproofing material". Being "foam like", relatively light, inexpensive and appearing quite dense, it has led most car audio retailers (in the older days) to believe that it can be profitably used for "soundproofing" applications.  In current times, where consumers are highly image-conscious and love idolizing high-end brands, other purpose-made, premium priced soundproofing materials are heavily promoted on the Internet. Meanwhile, for car enthusiasts with budget constraints, their favourite websites and forums have also heavily promoted Insulflex as an alternative "soundproofing material"...relatively cheap and easily available.

Insulflex is a closed-cell nitrile foam rubber for thermal insulation.
Being closed-cell and not a few inches thick, it is not an effective sound absorber, especially the low-frequencies. The manufacturer has specified its NRC (Noise Reduction Coefficient - related to absorption) as a merely 0.14.  The max is 1.0

And since Insulfex is not a heavy material, it does not possess the mass necessary to function as an effective noise barrier material (to block noise)..especially the low-frequency portion of that droning, rumbling tire/road noise. Effective sound barrier materials are minimally 1lb per sq foot (such as Mass Loaded Vinyl).

Nevertheless, Insulfex is still capable of noticeably muffling and reducing the amplitude of higher frequencies of tire and engine noise. If you're on a very strict budget and cannot tolerate heavy soundproofing materials in your vehicle, Insulflex one of the low-budget methods to produce noticeable results. 

My suggestion for low-budget soundproofing with Insulflex:
Use small pieces of damping sheets (eg Dynamat etc) to spot-damp your doors, firewall, fender hump etc, and then lay the maximum thickness of Insulflex on top that allows carpet to be re-secured.

On most Jap cars, my main targets to be Insulfex-ed in a low-budget job that can be done in stages (ranked according to importance)
1. Underside the hood.
2. All doors (ensure all holes are covered by damping sheets first)
3. Front kickpanel area x 2
4. Rear wheel hump x 2

Once you've done the above, and assuming your tires are not badly worn and your wheel bearings are OK, you'll definitely hear a noticeable improvement.

Tip: 
If your vehicle is externally parked for long periods in hot weather, Insulflex within your headliner is an excellent way to enjoy a cooler interior. Works great.  

How To Reduce Tire Noise/Road Noise

Road noise/Tire noise: This droning and rumbling noise is mostly produced by the tire tread's interaction with the road surface, and the noise is mostly low-frequency in nature. Your typical damping sheet (Dynamat etc) will never block or absorb such low-freq noise. It was never designed for these purposes. Neither will any closed-cell or open celled foam. For effective absorption of low-freq noises, you'll need at least a few inches thick of fluffy materials (such as jute, rockwool, fiberglass etc).

This common complaint (tire noise) should be your 1st target to attack in most modern vehicles. The strategy below gives the best Bang for the Buck results.

 Step 1: Wheel arches 
This area is the closest to the tire...the source of this noise. The shape of the wheel arch's interior and the air space within will amplify certain frequencies, and these will easily penetrate the metal into your interior. Spray each wheel arch with few layers of rubberized undercoating (3M,Bondo, Duplicolour, Sikagard etc). You can also use the brush-on type from many soundproofing materials manufacturers (eg StP's Mastic, Secondskin etc). Get this coating as thick as possible. Treat your wheel arch liners with the same product, attach a damping sheet to the underside of the liner, and stick a piece of 3M Thinsulate on top).

Step 2: Undercarriage 
Do the same thing as per your 4 wheel arches. The above Wheel Arch and Undercarriage treatment should always be your 1st soundproofing activity as you are addressing the areas closest to the NOISE SOURCE. The above will give you a significantly noticeable result without stripping any of your interior bits. Once you have done the above, and if you feel you want to improve it further, and you're on a tight budget... 

Step 3: Door hinge area
Open your front doors and look at the top and bottom door hinges. Look at the area between the 2 hinges and BEHIND them...there's usually a gap that leads into the front fender. This is a critical area, and hence, many car mftrs (especially VW) pay special attention to this gap. Squeeze any closed-cell, non-water absorbent material to totally seal this gap. Makes a huge difference in tire noise intrusion into cabin. VW uses foam blocks and even then, there's still some small gaps around these foam blocks. You can use silicone etc to ensure a good seal as lots of noise easily penetrates through the smallest hole.  Remember...we're on a tight budget and addressing the main critical areas pertaining to irritating road/tire noise.

Step 4: A, B and C pillars. 
Tire noise comes from the lowest part of the car, enters the hollow door sill, penetrates into the pillar's bottom and the noise shoots upwards to the interior roof. Hence, certain vehicle's A, B and C pillars are fully foamed or partially foamed at the assembly plant or have some kind of fluffy materials stuffed into them. Foaming the pillars is often recommended by retailers who're heavily into offering foaming services. The foam cannot block all frequencies and because its closed-cell nature, it can't absorb most low frequencies well either. Foaming can produce respectable results but bearing in mind the cost of foaming, you can stuff the A, B and C pillars with fluffy polyfill (used to stuff speaker enclosures) or even the new 3M Thinsulate which is light, highly sound absorbent and hydroscopic). Treating your pillars, especially the A pillar makes a significant difference in lowering tire and engine noise. Why? Engine noise easily penetrates your hood, and the oncoming wind carries this blanket of noise, and slamming it onto your windscreen (which transfers the sound vibrations onto the A pillars), and the external noises also penetrates the pillars and amplified by the hollow space within the pillars.

 The above 4 steps are the first few things you must do when addressing tire noise, and once done, anything else will be really labour intensive and could start getting expensive cos you might end up following the others who're doing the wrong things and using materials in the wrong manner. I will get elaborate on Step 5 a while later as its late now...Yawnnnn!

Truth About Soundproofing Your Car

Most information you obtained on vehicle soundproofing are MAINLY derived from the Internet....from articles and websites created by suppliers of soundproofing materials and car audio retailers who perform sound proofing jobs.

 As per usual marketing sense, their marketing objective is to:
1. Promote their brands
2. Increase usage quantity and usage of a wide variety of their materials.

Hence, you still see the outdated, old-school approach created by the early leaders in this industry where the entire car flooring and firewall are covered by shiny damping materials. Just imagine the weight increase and tremendous cost without any guaranteed results!.

The noise that envelopes you in the car interior are a combination of engine noise, tire noise, wind noise and external traffic noise. These MUST be kept in balance. Eg: Aggresively reducing 1 type of noise could make the other noises more apparent/louder. Even a Lexus is not 100% quiet, as a perfectly quiet car makes you feel uncomfortable, just like staying late at office with the air-conditioning and other stuff switched off. It gives that eerie sensation if you're not used to it. Complete silence can be deafening.

Due to excitement generated by the media, many car enthusiasts jump into "soundproofing" their vehicles using these "classic" methods and approaches such as using loads of costly and heavy asphalt and/or butyl-based damping materials (eg Dynamat,GSI etc), and slathering these materials all over the car. Many have convinced themselves that there's an improvement while others have been quietly disappointed. Many have even used materials for home roofing (Peel and Seal) simply due to its lower price, and believing that these are equivalent to damping sheets meant specifically for automotive sound damping without considering its effect in the longer term and adhesive quality.

Many car owners have their own approaches such as heavily doing up the 4 doors with damping sheets without even knowing IS the problem mainly contributed by the doors themselves!. Others will vigorously attack the floor. The above is the main reason why many car owners are experiencing the "high-end hi-fi syndrome" when it comes to vehicle soundproofing...a never ending, expensive pursuit to chase after different elusive targets. A never-ending game. In short, most owners have never investigated: 1. What is the main type of noise that annoys them? 2. Where is this noise mostly emanating from? 3. What's the most cost-effective method to give the most "bang for the buck" results? On modern vehicles, the No1 noise problem is mostly tire noise/road noise, and my next blog deals with this issue.