
What are standing waves?
Standing waves are the buildup of sound level (increased amplitude) at a particular frequency that results when traveling sound waves coming from opposite directions constructively combine to increase amplitude above that of the original waves. Standing waves occur when sound is reflected back toward the source at the original frequency. This is why it is important that soundproofing materials actually absorb the sound (by converting the energy they contain into heat) and not simply try to block it from coming through a wall. The number of times and the efficiency with which a sound wave is reflected will determine how high the amplitude will rise. In all cases it will be louder than the original sound produced.
The amplified sound you hear in a sea shell occurs because standing waves are formed as the interior of the shell reflects back the noise of the blood rushing through your ear.

For over a decade the name BARRIER has been associated with the highest performance and most technologically advanced thermal insulation in the world. Now BARRIER Ultra-dB™ offers the same quantum leap in noise control technology. BARRIER Ultra-dB acoustic insulation is a carefully engineered soundproofing material intended for those applications requiring superior performance without the size and weight of laminated foam and lead/vinyl products.
With BARRIER Ultra-dB acoustic insulation you get:
A wide frequency band solution
Sound is an incredibly complex thing. Varying frequencies, amplitude, intensity, harmonics, pressure level, dB(a), dB(b), dB(c), dB(m), dB(v), dB(spl), sone scale, phon scale and on it goes. For the tortured ear it all adds up to just one thing — NOISE. Those of us trying desperately to get some peace and quiet may find it hard to believe that there isn't some magic material capable of just blocking it all off. Unfortunately, while no such material exists, our Ultra-dB blocks sound so well, you'll realize you won't need magic.
While many materials block sound, no single material blocks noise. The problem is the frequency range. What we call "noise" nearly always consists of many different frequencies. The sound spectrum analysis on the right (click for larger image) shows a 3-cylinder diesel engine running at 2,800 rpms. The “noise” it emits includes frequencies ranging from 22Hz to over 11kHz. No single material can effectively block all these frequencies. The only way to attenuate this kind of noise is to select a combination of materials which work together to effectively control sound across a broad spectrum. In practice this is harder than it may seem since different materials grouped together change resonance characteristics and can respond in unexpected ways. When it comes to effective noise attenuation, it is the quality of the materials selected and the way in which they are combined that determines the performance of the finished product. As with all Glacier Bay products, superior engineering is the secret to the superior performance of Ultra-dB.
The physics of multilayer acoustic insulation materials

Noise is energy and, as you know, you can't just get rid of energy. What you can do is change its form. That's what acoustic insulation does, by changing the energy contained in sound waves into heat. The more effectively it does this the greater the sound reduction. To understand why BARRIER Ultra-dB works so much better than our competitors, let's first take a look at the basics of multilayer sound-control technology.
Multilayer “foam-vinyl-foam” type laminates are an attempt by manufacturers to try to attenuate a wider range of frequencies than would be possible with one material alone. The individual layers are often described by their functionality as the “absorption-damping-decoupling” layers. The “absorption” layer (nearest the noise source) is comprised of foam which is of a density that allows it to be moved (i.e. vibrated) by higher frequency sound waves. Energy is required to move the foam and this energy comes from the sound waves themselves. The frequency of sound which most effectively moves the foam is that particular material's "resonant" frequency. Consequently, it is the resonant frequency which is the one best attenuated by the material. Because they are located nearest the noise source, absorption layers also help to inhibit the formation of standing waves.
The resonant frequency of foam is quite high — above 250—500 Hz depending on thickness. Frequencies lower than that pass through virtually unaffected. Attenuating these lower frequencies is much more difficult and is the primary function of the “damping” layer. The damping layer used in conventional sound materials is very heavy (lead or a filled vinyl of similar density) and relies on high mass to provide a lower resonant frequency and harness the energy contained in these waves. The waves hit the damping layer and, as with the lighter foam, make it vibrate. Unfortunately, because of the weight of the damping layer, this vibration can create a new problem. If the vibrating mass is allowed to mechanically transfer energy to another surface (such as a wall or bulkhead) the noise is simply transferred through and radiated off the other surface. It is the job of the “decoupling” layer to prevent this from happening.
The BARRIER Ultra-dB™ difference
Conventional acoustic insulation materials work well if you use sufficient weight and thickness. There are many manufacturers and little difference between product performance other than the differences in the thickness and weight. The design goal of BARRIER Ultra-dB was to provide greater noise reduction in a thinner, lighter material.
It was necessary to find a way to better attenuate low frequencies without resorting to the high mass of conventional damping layers. What was needed was a lightweight material which would resonate at low frequencies and effectively dissipate that energy internally with a minimum of linear movement. To accomplish this is was necessary to get away from the type of uniform, molded "sheet" products (filled vinyl or lead) which are commonly used. The uniform nature of these materials limits their frequency range and requires that the entire sheet be moved as a whole to dissipate energy. This movement, as previously mentioned, introduces its own set of isolation problems.
BARRIER Ultra-dB solves the damping layer problem in a particularly ingenious way. Rather than using a uniformly molded sheet, our damping layer is a composite made up of randomly adhered elastomeric particles of varying sizes, shapes, weights, densities and durometers. When sound waves strike, different particles within the layer will resonate depending on the frequency of the wave. At any given frequency only a fraction of the particles vibrate. Each vibrating particle is loosely suspended between other particles, most of which do not resonate at the same frequency. This permits the energy contained within the vibrating particle to be dissipated into the adjacent material rather than through movement of the entire layer.
The result is better attenuation over a wider frequency range and without the problems associated with a single, heavy vibrating mass.
Pricing*
| Product | Thickness | Sheet Size | Price |
| Ultra-dB™ Flex | 1.5" (38mm) | 4.5' x 6' (137 x 183 cm) | $295 |
* All prices are f.o.b. Union City, CA. Additional packaging costs may apply to some orders.
Want to talk to someone about Ultra-dB sound insulation? Contact Glacier Bay, Inc.

