When a stone is thrown into the water we see surface waves spreading in circles. In the same way, sound waves or vibrations propagate from their source in spherical waves. These waves are picked up by the hearing system and converted into impulses interpreted by the brain.
|
 |
 |
Sound is characterised in different ways, but primarily in terms of intensity and frequency.
The intensity of sound is expressed in decibel (dB). A low dB value indicates a soft sound – a high dB value a loud sound.
The soft rustle of leaves in the forest corresponds to a sound level of about 20-25 dB. The intensity of normal speech is 55-65 dB while that of an aeroplane comes up to around 140 dB.
The threshold of discomfort for people with normal hearing is typically around 120 dB.
Frequency is defined as the number of vibrations per second. The higher the number of vibrations per second, the higher the pitch. The lower the number of vibrations per second, the lower the pitch. Pitch is called the frequency of sound. Frequency is expressed in Hertz (Hz).
Tones that are high in pitch are high-frequency tones (many vibrations per second). They are very important for speech intelligibility. The consonants of speech and overtones of vowels are primarily made up of high frequency components.
Tones that are low in pitch are low-frequency tones (few vibrations per second). Low-frequency tones mostly contribute to the perception of timbre and fullness of sound. The vowels of speech mainly consist of low frequency components.
The pleasant sounds we hear in our surroundings contribute greatly to our quality of life.
Communication plays a very important role in our lives. Not being able to communicate can lower one’s quality of life considerably.
Access to information (verbal or sounds) is an important element of everyday life. Lack of information may mean that you miss the train.
When sound is too loud, uncomfortable or unwanted, we perceive it as noise. Noise can ”stress” our entire system, reducing the quality of life.
A sound can drown out another sound, so that the softest sound is no longer audible. This is called masking. In rooms with noise, such as loud music, it can be difficult to hear speech. Here, the music masks speech and is therefore perceived as background noise.
SEE ALSO:
Sound intensityFrequencyDecibelSensitivity to soundAcoustic trauma
