Soundproofing. The very word is a ticking time bomb of misplaced expectations. To soundproof a room is a colossal, complex and costly undertaking.
Soundproof rooms ONLY exist in the very best of recording studios, in industrial applications like anechoic chambers, or in outer space where there is no air.
Sound-transmission mitigation – now this is a realistic goal. To what extent? For how much money? How much physical area will be required?
These are the questions that must be asked, answered and budgeted for before construction begins.
Air in, Air out
Would you like to be able to breathe in the room or apartment? If air can move freely between adjacent spaces, so can sound.
How will you reduce the transmission of sound between the shared ductwork of your heating and air-conditioning system?
Gaps and paths
An old adage of the acoustics industry is “If a 1/4-inch gap is left open below a door, 60% of the sound will escape...”
Sound is sneaky. It will attempt to escape from any room, by any path possible. Sealing all flanking paths (gaps, penetrations, door jambs, etc.) is a small but important detail.
In older wood-frame buildings – like single family homes – there are so many flanking paths that typically only a limited amount of transmission mitigation can be achieved. The entire house must be thought of as one big block, with all parts connected to all other parts.
If sound vibrations enter the walls and floors, those same sound vibrations will travel within the structure and possibly reappear somewhere else in the home. Stopping vibrations from entering structure is key.
The physical characteristics of frequencies are varied. High frequencies are very short in wavelength and have a small amount of power. Whereas, low frequencies are very long in wavelength and have a large amount of power.
Human hearing has the ability to hear all frequencies between 20 Hz. & 20,000 Hz. (approximately 9-1/4 octaves) – a very large range.
So why does this whole thing about wavelength and absorption matter?
1. There is no “Magic Material” that will absorb all frequencies evenly. In other words, absorption as a method of control MUST be considered as a multi-thickness and multi-materials solution.
“If you don’t like this answer – find another Universe!” In this Universe, Physics just works that way! This is not opinion; it’s Physics
2. Spoken word and voices, musical instruments and music itself, all have multiple frequencies within them. If we only control (absorb) certain frequencies in a room, then the other frequencies that are being produced are not controlled at all, or at best are minimally controlled.
Calculated and proportional sound isolation and frequency control, whether by absorption, trapping, diffusion mass and de-coupling or a combination of all, is the norm in a well-designed acoustic environment. This isn’t a sales-pitch – its just Physics...!
To read the full article by Peter Harper, click here.