Nature of Sound
Sound travels in waves of alternating high and low pressure all travelling in the same direction through a given medium, for example, air. They originate from a vibrating object, for example a drum, or a person's vocal cords.
There are two main properties of these waves that influence the way we hear them, the frequency and the intensity.
The frequency of a sound is how close the waves are, and determines the sounds pitch. The higher the frequency of a vibration the higher its pitch. Frequency is measured in Hertz (Hz) and humans can hear sounds between 20 and 20,000 Hz, with normal speech lying in the region of between 100 and 3000 Hz.
The intensity of a sound is how big the waves are, and determines the sounds volume. Intensity is measured in decibels (dB), and the point at which humans can hear sounds is defined as 0dB at 1000 Hz.
Loud sounds and hearing loss
Exposure to high intensity sounds leads to hearing loss by damaging cells inside the cochlea. Sounds with an intensity of over 90 dB require some hearing protection to be implimented. Sound becomes uncomfortable to a normal ear in the region of around 120dB and is painful when the intensity reaches over 140dB. The louder the sounds the more rapid the hearing loss. Most people fail to notice their progressive hearing loss until it is too late.
Take a look at our noise-o-meter on the right of this page to see if you could be damaging your hearing everyday.