How to Build a Recording Studio - Part 7: Acoustics
Sound, like ripples formed on water when a stone is dropped on it is a wave. If the waves are larger, the tone is lower. Lower tones, called bass frequencies, move in long wide waves while higher tones called treble frequencies move in a constricted, shorter wave. Human ear can comprehend sound of frequencies ranging from 20 Hz to 20 KHz. For instance, a piano has the widest range among all instruments, ranging from 39 Hz (low note) and 3 KHz (high note).
Measurement of sound is done in decibels (dB). A normal concert produces approximately 95-100 dB of sound and a noisy rock concert could produce a sound of 130 dB. This is more than the threshold of pain; don’t forget to put on your earplugs which are specially made to protect your ears when you are exposed to very high sound levels. It is Interesting to know that whales can easily produce sound levels of even 180 dB. So avoid proximity to whales and wear some ear protection when you are exposed to such loud noises.
In absorption a sound wave is soaked up by a certain material and is measured by its co-efficient rating. The higher the rating of the material, the more is sound that is removed from the affected areas in your room. The various parts of the room may need differing co-efficient rating. Studios are empty shells in the beginning. Hard walls and surfaces have to be treated to make a room that sounds great. For instance, studios commonly use theater curtains of 20 gauge. It is a dense velvet material, having excellent absorption capacity for high-end frequencies. The thinner materials can absorb higher frequencies. Thicker materials absorb lower frequencies. This is the reason for having thick bass traps of large sizes containing holes or ports or to block low-end frequencies.
The variety of designs and products used in the industry is endless. Wall panels are widely used for absorbing sound. These are fiberglass panels enveloped in a cloth fabric. Varying thicknesses and sizes are used in cases of problem frequencies. Here too, the thin materials absorb high end frequencies and thicker materials the low end.
This is opposed to absorption. Assume that the sound wave is striking a mirror and reflecting back. This favors a brighter tone. If there is too much of absorption in a room causing it to sound extremely dead, place hard surfaces like wood panels in strategic spots to enhance the sound in the room.
There are studios having hanging panels that can be reversed or flipped from reflective to absorptive and vice versa to alter the sound in the room at will. Vocals will need more absorptive, dead sounding room. Drums need a more live room. Drums create the opposite effect when absorption is used in a room that is small and tight producing a heavy sound of Pop drum.
These are only guidelines, not rules. Make use of your ears for deciding the best sound.