As I sit here writing this on size 18 font I realise that I am finally succumbing to Presbyopia Presby the Latin for Old and Opia the Latin for Eye I didn’t mind suffering with mild Myopia (short sighted ness) But Old Eye at 46 I’m too young to be Presby.
Presbycusis Old ear at some point affects us all aswell (At least if we live long enough). In fact it is eveident in our Twenties. Mosquito alarms designed to ward off teenage gangs work by blasting out a high pitch siren. These high pitch sounds can not be heard by people over 20 but drive younger people insane.
When we are born we can hear from 20hz to 20000hz and we start to lose our hearing from the high frequencies from day 1 by the time we in our 60’s/70’s this loss will have started reach in to the speech spectrum. At this point a bit like my arms are some times not long enough to read the small print, we will start to struggle to hear in noisier situations, some people mumble and the kids today don’t speak as clearly as they use to.
Between 2khz to 4khz is where a lot of our speech understanding comes from. This is where the human ear is most sensitive where we make speech sounds called Frictives and Plosives as opposed to the open mouth sounds we make in the lower frequencies. Check out the 10 letter word below with 50% of the letters included from the lower part of the speech spectrum.
_E_E_I_IO_
Now see how much easier it is with 50% of the letters from the higher range
T_L_V_S_ _N
High Frequency sound is also very directional as opposed to low frequency sound being Omnidirectional. Owls with their sharp hearing and Satellite Dish shaped face can pin point the high frequency squeak of it’s prey with deadly precision. It is this directionality which makes hearing people whose back is to you or somebody talking to you from the front whilst sat in the back of a car or from a different room when Presbycusis takes hold in older age.
Comments