Columns

By Lillian So Chan


Dripping

 

I can almost hear it…in an abrupt moment of that splash, a hundred strains of crystal pearl drops spraying into the moonlit night, twinkling as they break the tranquil air, wrinkling the perfectly rounded edge of the mirrored moon.

Such, is the power of sound – it enriches our experience and heightens our awareness.

Sound and music arouse emotions in our heart and paint imagery in our mind. Often a tint of passion in the tone of a greeting, a lingering note after the music fades, a suppressed annoyance in a courteous remark, and a heartbreak in an awkward moment of silence… conveys the meaning more than a thousand words.

The familiar footsteps, the squealing sound of an open door, the unexpected voice of someone from the past…our ears can distinguish more than 400,000 sounds.

We are constantly capturing the subtleties in our communications with others and in our environment through sound.

Accumulative effects of the insignificant

Sometimes, everyday sounds are so faint or so routinely in the background that we are no longer aware of their presence, or the effects they have on us.

I was seriously sleep deprived in my first year living in Canada. After having grown up in a noise-polluted, busy city with around-the-clock urban noises, I was deaf-founded in the silence of the night. It was too quiet.

The faint clicking of the clock and the dripping of the tap in the bathroom were magnified. I can almost hear that rhythmic dripping now. With every six counts there would be another drop…

It was much later that I learned that 20 drops of water is approximately one mL. Five mL is a teaspoonful. So in about an hour (depending on the diameter of the facet and how much water is allowed to come through the tap etc), 180 mL or about half a soft-drink can of water dripped away.

The accumulative effects of the insistent insignificant can spiral into mind-boggling amounts.

Both miniature and powerful

The components of a human ear are miniature, and their performance is amazingly powerful. The auditory system including the sensory organ of hearing and the sensory organ of balance – completed with receiver, amplifier, microphone, and a sophisticated, complex hydraulic system – is about the size of a pea.

The cochlea in the inner ear, responsible for hearing, functions like a soft, coiled, 35 mm (14 inches) piano keyboard with 20,000 keys.

Damage

The intricate and delicate workings of the human ear make it susceptible to damage. Increasing numbers of young adults and children are experiencing hearing loss. Daily exposure to loud music played on portable devices and frequent exposure to loud music events are suspected causes. Many are already experiencing hearing loss even though they do not consider sound defined as hazardous to be loud.

It is estimated that about half of the 28 million cases of impaired hearing in the US resulted from short term or chronic exposure to loud noise. Furthermore, about 30 million Americans are exposed to daily noise levels that pose a risk for hearing loss.

Worldwide, it is estimated that 16% of disabling hearing loss in adults is due to occupational noise.

Listening to an alarm clock ringing for 8 hours?

How much noise is safe then?

It depends not on what you hear, but on how you hear, when you hear, and how loud it is.

The US National Institute of Occupational Safety and Health defines hazardous noise as sound that exceeds 80-85 dB in loudness over an 8-hour workday. This loudness is the equivalent of an alarm clock at bed side, or a telephone dialing tone, or city traffic noise. Listening to these noises all day long is annoying, but poses no risk of hearing loss.

However, for each 3 dB increase in loudness, the safe exposure time is cut in half. Prolonged exposure to hazardous noise or a short exposure to loud, impulsive noise can damage the structure of the hair cells in the inner ear, resulting in permanent hearing loss.

Individual differences in the rate of change in hearing are large, showing that a genetic susceptibility may be a factor. But in general, the magnitude of hearing loss depends on the level of noise to which one is exposed, the duration and frequency of exposure, and the accumulative amount of exposure (numbers of hours) per day.

An average person is born with about 16,000 hair cells in the cochlea. Up to 30-40% of these sensory cells can be damaged or destroyed before any measureable hearing loss is detected. By the time it is detectable, the damage is permanent. Hearing loss due to hair cell destruction cannot be restored by the use of a hearing aid.

… May our worlds always be filled with soft voices, wonderful sound, beautiful music, and creative silence...

References


  • Chan, L (2007) Dripping; editorial, WellnessOptions magazine issue #33, p7
  • Chan, L; Radomski, M W; Donhoffer, H; Filosa, F; Abel, S; Cheung, R (2007) Health effects of noises; WellnessOptions magazine issue #33 p29
  • Daniel, E (2007) Noise and hearing loss: a review. Journal of School Health, May 2007, vol 77, p225-231American School Health Association