VRIJE UNIVERSITEIT BRUSSEL Acoustics - the Dept. of ...

PrefaceSound is caused by the vibration of air particles. Sound can also be representedas a wave, propagating in a certain media (air, steel, et cetera... ).Soundisaperfectmeansofcommunication. Spokenlanguageisanecessity inour contemporary society. It is difficult to imagine our world without sound.A total absence of sound (like in an anechoic room) feels weird although itcould be a blessing sometimes. Sound has many pleasurable aspects: listeningto your favourite music, a phone call from your friend, an aria of LucianoPavarotti, the growling of the engine of a sports car. It is clear that thenotion of a sound being pleasurable or not is subjective. The sounds emittedduring an activity will in most cases not hinder the executor. This samesound however, can hinder a person in the proximity. The interpretation ofsound is highly individual, meaning that it is a factor that is hard to takeinto account. For example; listening to modern music, played extremely loudcan be a lust for daughter or son; whereas it causes annoyance for father andmother. The lawnmower of your neighbour can irritate you while the soundof your own one doesn’t bother you. There is a thin line between sound andsound pollution. In other cases (like noise pollution on the shop floor) itis quite obvious. One could think of a distinction between sound and noisepollution on basis of the sound level. This is the way the difference is definedin current legislation. It is clear however that not only the sound level determinesif we are dealing with sound pollution. The time of day, the activityof a person and his/her mood play a role as well. A leaking tap can cause alarge irritation during the night, and no irritation at all during the day.i