What is an Anechoic Chamber and How Quiet Can It Be?
Busy creating the latest and greatest noise measurement technology
One of the things that we often talk about when we’re running ourCPTC (Cirrus Product Training Courses)is how our hearing works and we often end up talking about how, if there’s no ambient sound, we can feel uncomfortable and can become disoriented very quickly.
One of the best (or maybe the worst) places to experience this is in an anechoic chamber. During my time at the University of Salford, we used the anechoic chamber for testing and evaluating hearing protection, as well as subjecting each other to tests as part of our final year projects. Something that often became very uncomfortable very quickly.
Theanechoic chamber at Salfordhas been designed to be as quiet as possible and the background noise level is a very low -12.4dB(A). This is well below what most people would ever need to measure with a sound level meter. This low level is essential if you need to accurately measure very quiet noise sources or test equipment that makes very little noise itself.
These purpose-designed rooms are isolated from outside noise so that nothing can leak in and they are often floating on special mounts to prevent any unwanted noise or vibration from getting through.
Inside the chamber itself you’ll usually find that all of the walls, ceiling and floor are covered by long triangular foam wedges, which have been designed to absorb any noise that hits them, preventing any sound from bouncing back to you. There is usually a wire mesh floor so that you can walk in and use the chamber for measurements.
的效果是,你只听到the noise that you generate yourself. What this means in reality is that you can hear the blood pumping through your head, the creaking of your joints and quite often the noise of your digestive system. These noises are always present but they are masked by the background noises that we live with day in, day out. By removing the noise of normal life, we can hear the noise that our bodies make.
Professor Trevor Cox from the University of Salford explains how the anechoic chamber at Salford works in thisfascinating 360 degree video。Drag your mouse around the explore the anechoic chamber.
In 2015, Microsoft’s anechoic chamber was measured as having a background noise level of -20.3dB(A), a new world record verified byGuinness World Records。这个数字更令人印象深刻的是，大约-23db是我们星球上可能存在的最安静的水平。这是空气分子相互反弹时发出的噪音。
有一个interactive presentationon the Microsoft website that allows you to explore the chamber and find out more about how quiet this room really is.
Do you have a question for the Noise Doctor?Drop us a line(or just shout really loud) and we’ll see what we can find out.
Download theNoise Measurement Terminology Guideto expand your noise knowledge and make measuring noise simpler
Download theNoise Measurement Terminology Guide扩展您的噪声知识并使测量噪声更简单。
Clarke Roberts
He particularly enjoys writing content about product applications, including noise nuisance, occupational noise and environmental noise pollution.
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