While there have been various attempts to get around this problem, accept for now that genuine silence is both possible and can actually be identified by even the most ruthless hippopotamus hunter. The question still remains as to what we hear when we listen to black noise? John Cage famously used silence in 4:33 but that was to draw attention to the inescapable ambient noise that surrounds us. Other musicians such as Orbital have used silence as a humorous form of political protest against draconian laws or Burial to create anticipation towards more recognisable sound. Yet all of these seem to be using silence to draw attention to other sounds. They tell us little about the character of black noise.
We can return to the science that motivated the discussion in the first place and tiresomely point out that black noise refers to no audio signals being emitted from a noise generator. This begs the question however, as to why we should refer to no noise as black noise? As previously drawn attention to by Cage, it is practically impossible to hear silence and it is philosophically challenging to show that no sound exists at a particular moment. It might be that this whole endeavour is ultimately an absurd task.
After taking into account just some of the issues surrounding silence, there seems a more poetic case for arguing that there should be an association between colour and an absence of sound. What is genuinely interesting is not the properties or the possibility of silence but being able to describe how the silence itself actually sounds. With that in mind, it seems a sly joke the world has played on us; when considered in isolation, colour and sound, the two most essential physical facts of the world are as ineffable and as mystic as they are.
While most people are familiar with ‘white noise’ as the random static that can be heard on misbehaving electronic equipment, less are familiar with its more colourful sonic cousins. Audio engineers have historically assigned certain noise signals colour labels with rigid technical definitions. These range from the deep and shimmering grey noise to the harsh and shattering blue noise. This link between noise and colour is both charming and elegant but offers little insight into the nature of sound. However, the less strictly defined black noise just so happens to raise a unique metaphysical puzzle about how we hear the world.
Black noise refers to what is more colloquially known as silence. This arbitrary academic term may seem of little relevance to many but it raises a few interesting questions that have real world implications for musicians and music lovers. Is silence itself a noise or put more paradoxically, is an absence of sound a sound in itself? This simple wordplay cast by scientists equating a coloured noise with what intuitively would not be considered a noise, brings about a rare philosophical riddle that affects those outside of the ivory tower.
One interesting way of tackling the issue is to look to Bertrand Russell’s famous statement to a young Wittgenstein, concerning negative truths that there is ‘No hippopotamus in the room at present’. While Wittgenstein could point to Russell if he were asked, ‘Is it true that Bertrand Russell is in the room’, there is no thing that is a non-hippopotamus which he could point to. To show that, a professional zoologist would be required to be in the room caring for an African mammal The cunning might try and argue that one could point to everything that is in the room and show that a hippopotamus wasn’t any one of those things. Unfortunately that would require one to say, “There exists all these things in the room and nothing else” - the nothing else claim here, being just as difficult to justify. With black noise we will have an equally difficult time showing that no sound can be actually heard.