sounding off: your incredible ears

We live so much in our eyes these days that we underestimate and undervalue our most potent and primal sense: hearing. Here are three reasons we should place hearing back on the throne as king of our senses.

1 Hearing is first in time.
Hearing develops at just 12 weeks after conception according to French audiologist Alfred Tomatis. Long before we have ears, we are hearing our mother's heartbeat through every cell. (Even as adults we still hear through our whole bodies. Ears are just the specialists: we sense sound through our skin, bone and muscle, which is how the profoundly deaf world-renowned percussionist Dame Evelyn Glennie can hear with no ear function at all.) The cochlea, the engine of the ear, reaches adult size and full functionality just 18 weeks after conception, long before the eyes are effective. From that point we hear very well, and learn to distinguish our mother's voice - as well as the reassuring three-time beat of her heart (lub-dub-pause). Hearing is the first sense we create, and according to numerous near-death accounts it's also the last sense to dim when we die.

Interestingly sound comes first not just for human beings but also for the universe. In the first 380,000 years of its existence the universe was an opaque plasma of photons, electrons and baryons. There was no light because matter and energy were one, and all the photons were bound up in the plasma; it wasn't until the moment of decoupling when the expanding plasma cloud cooled to 3,000 degrees Kelvin that the photons were released and light came into existence. But there was certainly sound before decoupling because the plasma was a medium and there was plenty of vibration going on as the universe expanded unimaginably quickly, but not evenly. Had humans been able to survive there and listen, they would have heard the sound of the universe being born long before light existed.

Fascinating then that many of the world's spiritual traditions have sound coming before light at the birth of our world. The Old Testament has the heavens and the earth formless, empty and dark with the spirit of God hovering (alternative translation: vibrating) over them - and only then does God say: "Let there be light." The New Testament says: "In the beginning was the word." The Hindus say "Nada Brahma", one meaning of which is "the world is sound." The mystics of Islam, the Sufis, say that all form manifests from sound. Looking further afield, the degree of consistency becomes quite impressive, with sound being placed at the centre of creation by religious traditions from all corners of the globe including Aztec, Inuit, Persian, Indian, Malayan, Ancient Egyptian, Polynesian, Japanese, Chinese, Balinese, Tibetan and Ancient Greek.

While considering sound and time we may also reflect that the two are intrinsically linked in our hearing and our listening. Music, for example, has been called 'art in time'. Only in time can it exist. Hermann Hesse wrote: "Music is time made aesthetically perceptible." There is no auditory equivalent of a photograph; a sound in an instant is meaningless, so there's no way of compressing sound from four dimensions (three spatial plus one temporal) to two. Sound always requires time. This is true also of language, which further requires memory to have meaning. You understand my language by remembering what I just said and placing my words in that context. Vision, by comparison is inherently instant.

2 Hearing is first in space.
Sight is a directed sense. With our binocular vision we see in a cone in front of us, approximately 180 degrees wide and 120 tall. Hearing, by comparison, is completely spherical. Anyone can place a sound precisely in three dimensions. We have no 'deaf spot' because hearing is and always has been our primary warning sense, and because it is vital to our spatial awareness. These are the reasons that our hearing is on duty from before birth to death, with no rest at all. We close our eyes to sleep, but our hearing carries on working: we have no earlids because even while we are dreaming our hearing constantly scans and analyses the sounds around us. We're all familiar with waking suddenly because some small unfamiliar sound has triggered our lizard brain to alert us.

We discern a great deal about any space in a second or two from its acoustics: with eyes shut we can perceive walls and other solid objects from the tiniest sonic reflections. With practice this skill can approach that of bats or dolphins - as in the case of Ben Underwood, the blind boy in California who navigates with clicks.

Of course our ears are also our organs of balance, telling us which way is up at all times. Hearing and space are intimately and permanently connected in a potent and authentic perceptive process. This is why there are few aural illusions, and why that phrase is unknown - whereas 'optical illusion' is so familiar.

3 Hearing is far more sensitive
We see a spectrum of vibration from about 390 nanometres (violet) to about 780 nanometres (red). (A nanometre is one thousand-millionth of a metre.) The frequencies of these tiny waves range from about 380 terahertz (red) to about 770 terahertz (violet). (Tera = an old fashioned billion, i.e. a million million. Hertz = one cycle per second.) An octave is a doubling of frequency, so our visual range is surprisingly just one octave! By comparison a young human being with good hearing can hear from about 16 Hz to about 16 KHz, which is ten octaves. Our auditory range is thus ten times greater than our visual in terms of relative frequency.

Human hearing can perceive a huge range of intensity, with a dynamic range of 130 dB. A sound that causes permanent damage with short exposure (like a train horn at one metre, which at 130 dB will perforate eardrums) has a thousand million times more power than the quietest sound the average healthy person can hear (a mosquito flying away at 3 metres, or 0 dB). In contrast, the eye's dynamic range (which can also be measured in dB) is just 90 dB. The decibel scale is logarithmic, so in terms of intensity our aural range is 10,000 times greater than our visual.

According to Richard Norton at the University of Chicago the average human ear can distinguish 1,378 'just noticeable differences' in tone. By comparison we can distinguish just 150 hues of colour. On this measure hearing is almost 100 times as sensitive.

That's not all. Even the most tone-deaf humans can spot an octave, and many people with good pitch can identify a given note. Our hearing is not just absolute: unlike vision, it also detects and measures relative values. We have no idea when two colours are an octave apart, but we know exactly when two tones are. It may be that the inherent relationship between number and tone helped to give us the foundations of mathematical understanding as we started to understand vibration and fashion musical instruments, especially stringed ones. (Every note in the harmonic series is achieved through selecting perfect proportions of a vibrating string's length.)

This is the amazing sense which is being thoughtlessly assailed by increasing urban noise (doubling every twenty years according to Murray Schafer) and maimed by increasing headphone abuse (our current teenage generation may be the first to enter the workforce with a majority already suffering from serious hearing damage).

I believe that if we rediscover how astounding this precious sense is, we will start to value and nurture it, and the world will become a very different place. This is my passion and why I'm doing what I'm doing. I invite you to join me in a campaign to save our hearing.

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