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How The Hearing System Works.
Our hearing responds to oscillations in the air, which we interpret as sounds. The oscillations we can hear vary in frequency from approximately 35Hz to 15KHz (depending on age and losses) or, equivalently, in wavelength from 31ft. to 7/8in. Most eight-year-olds really can hear the nominal 20-20KHz we see in specs. The mechanisms of the hearing system are remarkable in their ability to sense oscillations so different in scale. .
The mechanical structure of the ear is a chain of transducers (energy converters) which convey the oscillations of the air to the sensors of the nervous system for data gathering and subsequent interpretation by the brain. Like other audio systems, the entire hearing system is subject to problems such as distortion, noise and progressive and catastrophic failure, however, if the system is operated within its design parameters then it will work well for a long time. Understanding the parameters will give you the knowledge you need to make judgements about your own sonic environment. .
Parts Of Speech and Hearing.
The function of the hearing system has been developed by evolution to serve, among other needs, our need to communicate, so speech and hearing are linked. Understanding the functions of the hearing system helps one to understand the causes and effects of hearing loss. .
The hearing system is divided into two subsystems which respond to the two modes of speech. The low frequency subsystem identifies pitch and the characteristic resonances of the person speaking (vowels, chest and head tones), while the high frequency subsystem identifies stops and starts (consonants, mouth sounds). The brain integrates and interprets both modes to form an image of words. .
Why We Like It Loud.
It turns out that loud sounds directly affect our autonomic nervous system (also called involuntary - it controls the body functions that you hope never stop, like breathing and digestion), in a way similar to many stimulant drugs.
