Why do acoustic booths and soundproofing booths using acoustic foam or felt produce a "boxy" or "boomy" sound ?
Many people who have tried acoustic booths that use acoustic foam or felt for interior acoustics later decided to switch to our VocalBoothToGo acoustic booths and soundproof booths, which use VocalBoothToGo acoustic blankets (acoustic curtains) for interior acoustics, providing much better sound quality.
According to experienced actors and voice-over artists who have had the opportunity to compare different options, foam acoustic booths (even the larger ones) cause a "boxy" or "boomy" sound. When testing the VocalBoothToGo acoustic booths, they achieved high-quality balanced sound, which led to clearer and higher-quality recordings.
Why do portable acoustic booths from VocalBoothToGo outperform foam booths?
All booths from VocalBoothToGo surpass foam-lined booths in many aspects: portability, ease of assembly, practicality, durability, and resilience. But the most important aspect – sound quality – requires a more detailed examination.
Comparison of booths using Acoustic Foam or Felt and acoustic blankets (acoustic curtains) from VocalBoothToGo
We decided to conduct a comparison of foam booths and VocalBoothToGo booths, which use VocalBoothToGo acoustic materials.
The effect of booth construction and sound reflection
Acoustic foam must be attached to a solid surface, which partially reflects the sound back, even if with less energy.
In contrast, booths using acoustic blankets do not need solid walls to attach the material, as the blankets themselves form the wall, allowing the sound to pass more easily outside the booth while the acoustic blankets absorb surrounding sounds and protect the microphone from sound reflections.
Internal volume
Another difference is the internal space of the booth. Foam booths, due to the thickness of the foam, have a very small internal volume, which causes a "boxy" sound. Sound waves reflect, even though they are dampened.
VocalBoothToGo booths can have significantly larger internal space with the same external size, and the actor is surrounded by sound-absorbing material in a 360-degree radius, creating a more isolated environment.
The physics of sound absorption
The most important difference lies in the method of sound absorption between foam and blanket materials. Both types of materials convert sound energy into heat, but with different mechanisms.
Foam materials (acoustic foam)
Foam absorbs sound waves by trapping them in its pores and channels. Sound loses energy due to air friction against the channel walls. This process increases air resistance, which reduces the amplitude of the waves.
Fibrous materials (VocalBoothToGo acoustic blankets)
Fibrous panels, such as VocalBoothToGo acoustic blankets and curtains, work differently – sound waves try to move through the individual fibers, losing energy as they do so. This process is comparable to ocean waves hitting seaweed: the energy of the waves is used up by their movement, eventually calming them down.
The importance of sound absorption charts
We examined charts showing sound absorption of acoustic foam and acoustic blankets to better understand where the so-called "boominess" occurs. Below, we present absorption curve comparisons for different thicknesses of acoustic foam and VocalBoothToGo acoustic blankets.
Sound absorption chart (Fig. 1)
In the chart, you can see that the absorption curve of the VocalBoothToGo acoustic blankets is almost linear, meaning that mid to high frequencies are absorbed evenly at levels of 90-100%. On the other hand, the acoustic foam charts are nonlinear, with mid frequencies being absorbed more intensely than high ones, leading to uneven absorption.
The effect of acoustic foam thickness (Fig. 2)
As the thickness of the acoustic foam increases, mid frequencies are absorbed even more, which amplifies this unbalanced effect.
Conclusion
Foam acoustic booths often result in so-called "boomy" and "boxy" sound due to uneven frequency absorption. In contrast, acoustic and soundproof booths using VocalBoothToGo acoustic blankets provide more even sound absorption and better recording conditions. This difference is especially significant in small enclosed spaces, where foam booths more frequently create an unnatural sound.