Have you ever screamed into a pillow? Well I do constantly and if you do, you’ll notice that it sounds very muffled. This is due to the acoustic qualities that absorptive material removes. Absorption is great at removing higher frequencies. It will take some of the low end out but because the physical sound waves are larger in the lower end, they tend to pass right through.

Bass Trapping:

Another example is hearing a nightclub from the outside. The soft furnishings inside the building remove most of the higher frequencies but the low beat of the music still travels through the walls.

So how do you get rid of the low end? This is the hardest of the frequency ranges to deal with. The wavelengths of low frequencies are so large and the energy they produce is greater. Wikipedia states, “For sound waves in air, the speed of sound is 343 m/s (at room temperature and atmospheric pressure). The wavelengths of sound frequencies audible to the human ear (20 Hz–20 kHz) are thus between approximately 17 m and 17 mm, respectively.”

This means that most the low end of the audio coming out the speakers in the studio has a wavelength that is longer than most rooms. This typically creates a build-up of low energy at the corners and walls of the rooms called ‘standing waves’. The treatment used to deal with these frequencies are bass traps. They normally consist of corner pieces placed in the corners of the room. The idea is for the bass frequencies to pass through them and get ‘trapped’ in the corner pieces before they come back in the room.