The science of acoustics is the study of sound and how it carries or is heard in an enclosed space. The goal of studio design is to insure that sound will behave in a controlled, predictable manner. Understanding the science of acoustics is the first step in the design of a recording studio.
Sound is a vibration which creates a wave motion in the air. The frequency and length of an audio wave determines the pitch of the tone. With a low tone, the frequency will be slower and farther apart. If it is a higher tone, the frequency will be faster and closer together. Doubling the frequency of a note moves it up an octave in musical terms.
A tone frequency is measured in cycles per second, or Hertz Hz. The extreme ranges of frequencies extend from 0 Hz up to hundreds of thousands of cycles per second. Most humans cannot hear the extreme frequencies of tones, however, just because we cannot hear a tone frequency does not mean that it is not important in sound, it still contributes to the sonic experience in some way.
Science tells us that human hearing is generally accepted to extend from 20 Hz to 20 kHz, so for the treatment of studio acoustics design we are generally concerned with the frequencies that fall into the human range of hearing or lower.
In the science of acoustics, wavelength is the measure of an audio wave’s physical length; the lower the frequency, the longer the wave length, and the higher the frequency the shorter the wave length.
|20 Hz||56.3 feet|
|60 Hz||18.8 feet|
|100 Hz||11.3 feet|
|160 Hz||7.0 feet|
|320 Hz||3.5 feet|
|500 Hz||2.3 feet|
|1 kHz||1.1 feet|
|2.5 kHz||5.4 inches|
|5 kHz||2.7 inches|
|10 kHz||1.4 inches|
|20 kHz||0.7 inche|
These measurements are important when you are considering studio design because wavelength in combination with phase affects where there will be problems in an enclosed space.
According to the science of acoustics, the term phase describes the relationship of two sounds or signals in time. An audio wave travels in a continuous series of peaks and troughs whose progress is measured in degrees.
If two waves are traveling in phase, they reinforce each other. If two waves are traveling out of phase by 1 degree the result is a thin or hollow sound. If two waves are traveling out of phase by 180 degrees, they cancel each other out, resulting in silence.
The science of acoustics influences the use of specific construction materials and absorption treatments to aid in the control audio wave reflections.
Under normal conditions, when audio waves travel through the air and encounter a surface, for instance a wall; part of the audio wave will be absorbed by the wall, part of that audio wave may be reflected, and oftentimes that audio wave will pass through or around the surfaces of the wall and exit to the outside.
Add to that mix, audio waves reflecting from the many different surfaces in a room in various directions, and the result is a jumble of acoustic sound reflections which interfere with the clarity of the sound.
As you can see, the science of acoustics is complex and you have been presented with ‘just’ the basics. In the process of building a recording studio, or retrofitting an existing space, it is important to have a basic understanding of the science of acoustics.