The knowledge about noise
basis CNS8753 test specification. As shown in the sketch placed fan in background noise below 15 decibels of no sound in the room, a 1 meter distance noise meter, measure the suction fan surface, through the computer to collect measured data after the draw materials and sound pressure a prospective trend diagram can, octave band sound pressure level must chart and so on.
how noise said the strength of the human ear to listen to voa, actually varies with the frequency of the sound, for example, in 1000 hz people particularly sensitive to the ear, so the same sound pressure of the two different frequency, that the frequency of 1000 hz its volume is bigger. What the difference between music and noise is sounds comfortable or not, the sonic and not two. The human ear can hear the voice of intensity level ( SIL) Can the type said: SIL = log I/Io ( Bel) Or lO the log ( I/10*- 12 ( W/m*2) ) The Db Io: hear the voice of minimum intensity ( 10 * - 12 ( W/m*2) ) I: the intensity of the sound < W/m * 2 > in addition, also can use the sound pressure, said: L = log p * 2 * 2 / Po < Bel > or < dB > 10 log p/Po Po: minimum can listen to voa press < N/m * 2 > p: sound pressure < W/m * 2 >