The Colours of Noise - Blue
Noise is an important concept in engineering.
Many of the challenges in designing certain technologies, instruments and machines come from needing to extract an information signal from a background of unwanted noise. Assigning colour to noise assists engineers in signal processing by giving certain forms of noise recognisable qualities.
The noise colour spectrum.
The noise colour spectrum operates in a similar way to the spectrum of light. The sound spectrum begins with white noise, which is analogous to white light. We know that white light is a random combination of all possible colours, and it follows that white noise is a random mixture of many different frequencies. Because of this, white noise has a low information signal and a muddy quality.
White noise has a dampening effect, drowning out other sounds. We’ve all heard white noise – the hiss of an untuned FM radio, the background noise on a bad recording, the static sound of a noise machine.
The analogy naturally extends to other colours. Any kind of filtered noise can be called ‘coloured noise’ in the sense that it is not white noise – it has other qualities, textures or notes. This is where blue comes in.
The crucial role of blue noise.
Blue noise, also known as azure noise, gets its name from optics. The colour blue is on the higher end of the light spectrum. Similarly, blue noise has a strong shift in energy toward the high end of the sound spectrum. Blue noise has a high concentration of treble with very little bass.
Blue noise is a fascinating one, because while it’s a fairly boring sound it plays a crucial role in engineering. Because it is made up of very few low frequencies and a lot of high frequencies, blue noise can be difficult for the naked ear to discern. The common example used is the high pitched shhhhhh sound a kinked hose makes when it’s spraying water. At high volumes it can be harsh and even unbearable, like a loud whining hiss.
On the other hand, blue noise has important applications in sound engineering. The analogy is once again with the visual, because if you arrange retinal cells in a blue pattern you get good visual resolution. Following this, blue noise can be applied in a process known in sound engineering as dithering. Put simply, dithering is a way of smoothing out the audio signal to minimise distortion.
Noise control is at the heart of what we do.
Thinking of noise in terms of colour gives us greater control over the sounds we want to attenuate or amplify. HVAC Attenuation puts control and craft at the heart of our production. Our attenuators are designed and manufactured to order in Australia and rigorously tested for quality. We are also getting ready to provide dedicated selection software for your product which enables you to undertake detailed sound analysis (more on this soon).
Noise control is an art. And just as a painter has brushes, turpentine, a palette and easel, having the right tools at your disposal is essential when considering sound control or minimisation.