Can Auralex Studiofoam Wedgies Be Top Performing Soundproofing Foam?

Auralex Studiofoam Wedgies is considered by Auralex as “a great solution for spot treatment of sound studios”. They only offer Wedgies in one color, charcoal gray, and one size, one foot by one foot. However, in our simulations, we have found that Studiofoam Wedgies come closest to what we termed “narrow wedge” soundproofing foam. In our simulations, we often found that the narrow wedge foam performs better than what we termed “regular wedge”. Regular wedge soundproofing foam would correspond to the Auralex Studiofoam Wedge soundproofing foam.

Auralex notes, correctly, that Studiofoam Wedgies have a larger surface area than Studiofoam Wedges. This is true. A larger surface are does, in certain circumstances, improve sound absorption. Studiofoam Wedgies have a larger number of wedges per foot than Studiofoam Wedges. Thus, not only is the surface area greater, but also the “wedge angle” in Wedgies is less than the “wedge angle” in Studiofoam Wedges.

Let’s go into more details of the claims of better performance, and let’s review Auralex Studiofoam Wedgies, and compare them with their counterpart Studiofoam Wedges as we go along.

Dimensions, Material, Density Of Auralex Studiofoam Wedgies

Auralex Wedgies come in 1 ft by 1 ft squares. There are 15 wedges in each. This is more than 12 wedges per two foot in Auralex Studiofoam Wedges. This means that the base of each wedge in Studiofoam Wedgies is 1.6 in. long. Each wedge’s height is 1.5 in. A relatively larger height makes Auralex Wedgies fall under the “narrow wedge” category. We will see down below that such narrow wedge foam has better acoustic properties, especially for critical lower frequency where speed of sound diminishes and the foam surface geometry, not just foam surface area, starts to play a greater role.

Wedgies are made of high density open cell polyurethane rubber material. Its surface density is 0.83 kg/m². While this is a relatively high density for a foam, Auralex Wedgies is still a featherlight material, and it is very easy to mount or glue on the walls and ceilings.

Speed Of Sound And Dispersion In Soundproofing Foam

Speed of sound in polyurethane foam actually varies with frequency of sound. This is the meaning of the word “dispersion”. This behavior is quite unusual. In general, speed of sound in acoustic foam will be lower than speed of sound in air. The speed of sound actually tends to approach zero as frequency of sound approaches zero. Practically, this means that for very relevant frequencies in the 100 Hz – 300 Hz, where fundamental frequencies of both male and female voice, as well as fundamental frequencies of many musical instruments, lie, the speed of sound can be as low as 100 m/s or less, compared with the speed of sound of 330 m/s in air.

Sound Absorption And Noise Reduction Coefficient

In the table below, we compare sound absorption coefficients of Studiofoam Wedgies and Studiofoam Wedges.

Role Of Surface Area And Shape

As Auralex states, due to 15 wedges per foot in Studiofoam Wedgies, as opposed to lesser number in regular Studiofoam Wedges, the Wedgies will have larger surface area. That is true because each wedge adds approximately equal amount of surface area. However, for absorption, it is not only the surface area that matters, but also volume, and, in particular, the angle of incidence of the sound wave onto the wedge surface. Due to the larger number of wedges per foot in Auralex Wedgies, and due to the same height of an individual wedge, the wedges in Wedgies are significantly narrower. We call this type of wedge foam a “narrow wedge” as opposed to “regular wedge” in Auralex Studiofoam Wedge soundproofing foam.

Because of the top angle of the wedge is smaller in Wedgies, the same incoming sound wave will impact under a much different incident angle, and will be sent upon transmission into the foam in a significantly different direction. Because of that, its path could be much longer or shorter inside the foam, therefore the sound could be absorbed much more or less. We will study these differences, and how they affect optimal placement of Auralex Wedgies in the recording studio, below.

Sound Absorption Of Auralex Wedgies For Various Angles Of Incidence

Absorption At Normal Incidence

Figure below shows a simulation of a normal incidence of a sound ray

onto a narrow wedge, Wedgie-like acoustic foam. We observe that it is possible at certain impact locations, that the normally impacting sound ray (in red) will be partially transmitted into the foam, then will totally internally reflect off the bottom of the foam, then totally internally reflect off the other, left, side of the narrow wedge, two wedges away. Then, it will bounce back to the right, pass two wedges in total, and do one more circle back down into the bottom of the foam, and then experience another loop before it finally exits the foam back into the room. This long, double, loop means a long path through the absorbing foam, which means high absorpti
When we compare these results with [Auralex Studiofoam Wedges review] the review of Auralex Studiofoam Wedges, we notice some of the same characteristics, and some differences. The multiple loops made by the sound ray can be observed with Studiofoam Wedges as well, though the details of the directions are different. There is no apparent clear winner when it comes to absorption at normal incidence at low frequencies. This is also seen in Table above where Wedges performs better at 100 Hz, 160 Hz and 200 Hz while Wedgies performs better at 125 Hz, for the normal incidence sound.

Absorption At 15 Degrees

In the figure below a 15 degree incidence onto a simulated Studiofoam Wedgies

geometry soundproofing foam is shown. We observe that the part of the incident wave that refracts into the foam on the right behaves similarly as the normally incident wave behaved. It bounces off of the bottom surface, hits the opposite side of the wedge on the left and partially exits at an 15 degree angle to the left, and partially internally reflects back into the wedge, and makes another loop back to the bottom of the foam and back into the wedge. This indicates good absorption for the part of the wave that makes into the foam upon initial incidence.

The part of the impinging wave that reflects off the wedge on initial approach makes it easily into the neighboring wedge on the right, and then starts a trip at a low-slope angle toward the right edge of the foam tile, where it reflects off the vertical side. This nearly horizontal, long passage through the foam makes for good absorption too.

Absorption At 30 Degrees

In the figure below we see that the effect of “looping” back and forth

between the wedge side and the bottom side of the foam is still there, but less pronounced. Instead, as compared with the 15 degree incidence and especially normal incidence, we see that, because the 30 degree incident wave is closer to being normal to the wedge side on impact, more of the wave refracts into the foam, and, likewise, more of the wave exit on the left after just one internal reflection on the bottom of the foam. This is the behavior of the flat foam, a foam with the flat surface, and is the so called specular reflection. Since a lot of the sound exits back into the room after just one reflection off the bottom, the absorption is less than that at 15 degree incidence.

Absorption At 45 Degrees

Figure below shows what happens when the angle of incidence is 45 degrees.

At this angle, it becomes very likely that the incident wave will refract into the foam (due to near-normal incidence onto the wedge surface) and then totally internally reflect off of the opposite side of the same wedge. This is shown in the figure. After that, the wave bounces off the bottom of the foam and exits out of the neighboring wedge to the right. This, again, is a typical reflection behavior in specular reflection. The path through the foam is short, thus absorption will not be great at this angle of incidence. Likewise, the dispersion is not great as the majority of the wave will reflect back obeying the law of reflection.

Absorption at 60 Degrees

Figure below shows a simulation of a 60 degree incidence onto the Studiofoam Wedgies type

foam tile. Note that the elements used did not allow to simulate the entire tip of the wedge, which makes the actual path a bit different, but the main conclusion still stands. The sound ray enters the third wedge from the left at an 60 degree angle from the normal, which is nearly normal to the surface of the side of the wedge. The wave enters the foam with little reflection, and then totally internally reflects off the other side of the wedge, the bottom of the foam, and off the neighboring wedge. It then repeats the loop, but at the next wedge.

This bodes well for absorption as the wave is trapped in the foam along a relatively long path. As seen in the figure above, the sound does exit back into the room, but at a variety of places and at a variety of angles, so the diffusion is good.

Absorption At 75 Degrees

The figure below depicts the path of the sound wave as it enters the foam at a 75 degree angle

of incidence (measured, as usual, from the normal). The incoming wave transmits under about 90 degree angle into the side of the foam on the right. The wave then totally internally reflects off of the left side of the same wedge. It continues down toward the bottom of the foam. There, it nearly totally reflects back up and completes the internal reflection loop. This loop repeats again. Due to this looping, the path of the wave will be quite long inside the foam. Therefore, the absorption will be significant. As one can see in the figure, the diffusion is looking good as well due to a great variety of angles in which the sound wave finally enters back into the room. This result compares favorably with the result for a “regular wedge”, or Auralex Studiofoam Wedge type foam.

Conclusion: Placement Of Auralex Studiofoam Wedgies

Based on the results above, we can see Auralex Wedgies being used effectively in many different situations. They show best results for angle of incidence around 15 degrees. The simulation shows Auralex Wedgies absorbing well at 60 and 75 degree angles of incidence as well. The Wedgies seem to perform well at normal incidence. They seem to do better at 60 to 75 degree incidence. Whenever possible they should be used instead of regular wedge foam at these angles. For more information on placement or soundproofing foam, see Soundproofing Foam Placement For Recording Studio.

Bottom line, we find that, Studiofoam Wedgies can be used effectively for much more than “spot treatment of sound studios”. Due to their narrow wedge structure, they have unique capacity to absorb sound at low frequencies. We have showed that for certain angles of incidence such as near normal, and for 60-75 degree incidence. Their diffusion properties for these angles of incidence are superb also.

Fire Retardancy

Studiofoam Wedgies are made of open cell, polyurethane based foam that is fire retardant. We could not confirm that they have A Rating for Fire retardancy. We suspect that they do have A Rating. After all, the Auralex Studiofoam Wedges have A Rating. See also recent ASTM E-84 Fire Rating Test report Auralex Rating).

Durability

Unlike some other soundproofing foams, Studiofoam Wedgies are not made of melanine but of polyurethane. Therefore, they will be durable and will not crumble over time.

Appearance: Colors And Look

Auralex Studiofoam Wedgies are only available in charcoal gray color. This color will match other colors that are available for other Auralex foam products.

Accessories

We recommend Foamtak spray-on adhesive to attach Wedgies directly to the wall. You apply Foamtak lightly to achieve a temporary mount. You apply it heavily for a more permanent mount.

Availability

Auralex Studiofoam Wedgies are available in single packs and four packs at SamAsh.com.