We humans are a noisy bunch. Our unwanted sounds, more commonly defined as noise, have been echoing around the planet since before the Romans banned chariots from their paved streets (as their clatter disrupted sleep and caused annoyance). The truth has always been that we cannot close our ears as simply as we can shut our eyes. Looking away from the crescendo that started with, barely perceptible, wooden wheels on cobbles is not an option, especially as it has since amplified and spread to every corner of the globe and the skies above.
Gordon Hempton says that no place on earth is completely free of all human sound, all the time. The acoustic ecologist and founder of the non-profit One Square Inch, recorded the sound of aircraft from deep within the Amazon rainforest as well, as remote parts the North Pole. His work to find the quietest places on earth, revealed only 12 places in the US that are noise free for intervals of 15 minutes or more. Wisely, he only published the names of five, no doubt to preserve the peace for himself in the others.
As that wall of noise grows, so the science of acoustics becomes ever more salient. According to the experts at the IOA, the definition of acoustics is the “generation, transmission and reception of energy in the form of vibrational waves in matter”. A somewhat dry description of a very complex subject that requires expertise in areas as diverse as building design and wind farms. Acoustic engineering could also be described as the management of sound, be it damping reverberation in a concert hall or reducing external sound in a protected area. Acoustic doors play a crucial role in sound management.
While, for convenience, we describe some door-sets as acoustic, they may be better defined as sound attenuating doors. Sound attenuation (or sound insulation) is the prevention or reduction of the transfer of sound through a structure. Generated in different frequencies, which can be identified in pitch change, what we consider to be the loudness of sound most often refers to sound pressure, the measurement of which is expressed in decibels (dB). When sound strikes a surface, some of it is deflected, some of it absorbed and some passes through. Sound that is deflected is known as reverberation, sound attenuation is concerned with controlling the amount that passes through structure.
Some materials have better sound insulating qualities, but all building materials have some. So, although performance varies, walls are generally good sound attenuating barriers. However, gaps in walls designed to enable traffic or light, obviously also allow airborne sound to pass through. Where sound attenuation may be an issue, some door-sets have been specially designed to reduce the airflow across the gap to improve background noise levels.
The design of these doors can vary, some use mass, denser materials improve performance, while others use a combination of air gap and material layers, which are more effective for a wider range of frequencies. Attenuation is also influenced by factors such as: configuration; size, materials, hardware, glazing, sealing system, surrounding structure and quality of installation, making precise performance difficult to predict.
Available in 75mm and 100mm thickness, Acoustidor is certified to EN ISO 140-3 and offers sound attenuation from 41db to 56db. Made from galvanised steel sheeting, to reduce noise, it is constructed with a very efficient combination of air gap and insulation layers, augmented by an effective double door seal. It is effective for frequencies between 63Hz to 8000Hz which adequately covers our ears areas of maximum sensitivity which is 3 to 4kHz. It is a versatile solution for sound insulation barriers.
Ironically, the only place where it is possible to escape from human made noise, for any length of time, is inside a human built anechoic chamber. Sound proof and sound wave absorbing, they can be very disconcerting and uncomfortable for ears more conditioned to the constant din. Acoustidor may not be able to produce that kind of absolute silence, but it can and does keep the noise down a bit.
“…only 12 places in the US that are noise free for intervals of 15 minutes or more”