There is a great variety of sound dampening foam panels available in the marketplace. When you are building out a sound recording studio, you will have questions such as these: What type of sound dampening foam you want to use? Where to buy soundproof foam? Where to place sound dampening foam in your recording studio.
We have looked into some of the best acoustic dampening foams out there and investigated the differences between them as far as the sound propagation in them, sound reflection, sound refraction, and, ultimately, sound absorption and sound diffusion. Among these properties, sound absorption and sound diffusion are the most important.
When your acoustic damping foam absorbs sufficient amount of sound, you don’t have to worry about what happens with the remaining sound that reflects back into the room. However, when insufficient sound is absorbed, it becomes important that the reflected sound reflects in a diffusive manner.
Diffuse reflection means that the sound reflected off of the sound dampening foam reflects in many different directions. Then, before it finally reaches the microphone, it will have more opportunities to hit another sound dampening foam. The sound dampening foam will absorb it further then. When the diffusion is insufficient, it can happen in the worst case scenario that most of the sound from the sound source reflects directly into the microphone, which would cause a clear, most likely unwanted, echo.
Sound Dampening Foam Placement To Reduce External Noise And Internal Echoes
There are two aspects of sound dampening. The first, reduction of noise coming from the outside of the sound recording studio. The second, reduction of reflections from the walls to reduce echoes, reverberation, and buildup of standing waves all of which will adversely impact the recorded sound.
Placing sound dampening foam on the walls would have to be wall-to-wall in order to be completely effective. We have found that … are the best foams to reduce the intensity of the outside noise. Check out our more detailed findings in this post: Sound Absorbing Foam Panels For Reduction Of External Noises. The most important reason for placing sound dampening foam, however, is to reduce reflections off the walls of the sounds originating inside the recording studio.
Placement Of Acoustic Dampening Foam To Reduce Internal Reflections
We have simulated absorption of sound that impinges on the acoustic dampening foam at a certain angle off the normal. We simulated normal incidence, where the sound impinges at a right angle to the foam surface, as well as incidence angles of 15, 30, 45, 60 and 75 degrees. These incidence angles cover incidences between normal and grazing incidence. The important frequency in the simulations was around 240 Hz, corresponding to speed of sound in the foam of about 140 m/s.
We have found (see post Acoustic Sound Foam Placement In Recording Studio, Part 2, Oblique Incidence) that for normal incidence and 15 degree incidence, as well as for 60 and 75 degree incidences, the “vertical wedge” foam absorbs best, as long as it is oriented with the vertical side toward the source of the sound. We also found that for the 30 and 45 degree angles of incidence, the “narrow wedge” foam absorbs best. In our simulations we found that the foams that absorb the most also diffuse the reflected sound the most.
Based on these findings we envision positioning sound dampening foam in the recording studio in positions relative to the source of sound which can either be the vocalist, the musical instrument, or a loudspeaker. We present the positioning of panels in the figure below, as an example.
The figure represents a schematic top view of the recording studio. The source of sound is toward the left, in the middle. The front wall is closer to the source, and you can see it on the left side. The side walls are on top and bottom of the picture, and the rear wall is to the right. The black lines originating at the source of the sound represent directions in which we should place vertical wedge dampening foam panels. The orange lines represent directions in which we should place the narrow wedge foam panels.
We see that for the front wall, sound only hits the wall under the normal, 15, 30, and 45 degree angles of incidence. The sound hits the rear end of the side wall under the 60 degree and 75 degree angles also. The angles under which the sound hits the rear wall are between 0 (normal incidence) and 30 degrees only.
Placement Of Sound Dampening Foams On Side Walls And Rotation Of Foam Tiles
In the figure below
we show a view of one of the side walls. Again, the position of the sound source is further on the left. The front wall is on the left, and the rear wall is on the right. The sound source is assumed to be positioned somewhere at the mid-height of the room. The black panels represent the narrow wedge panels while the orange panels represent the vertical wedge sound dampening foam panels.
In this view we can also show the optimal rotation of both types of foams. Our simulations show that in order for sound to enter the foams best, the vertical wedge foam should face the source of sound with the actual vertical side. Likewise, the narrow wedge foam should be oriented in relation to the sound source such that the ridge of the wedge is perpendicular to the direction of the incoming sound. This is shown in figure above by orienting the panels above and below the mid-height of the room, we will achieve better sound absorption.
Placement Of Sound Dampening Foams On Rear Wall And Tile Rotation
In the figure below
we show the suggested placement and rotation of sound dampening foams. This is for the rear wall. Again, the black foams are the vertical wedge foams. They are oriented toward the source of sound with their vertical side. The orange colored squares represent the narrow wedge foams. These are oriented such as to face the source of sound with one of their sides. A similar suggestion about orienting wedge foams holds for the front wall as well.