6. If the intensity of sound from a source A has a loudness of 26 dB, then what is the decibels of a source B that is 100 times more intense? FEELING 7. Find is the loudness level in 120 120 110 phons of a 10,000 Hz pure tone at 100 100 30 dB in the chart: phons 90 BO 80 70 INTENSITY LEVEL (de) LOUDNESS LEVEL (phone) 60 60 Then what should the intensity 50 level (in dB) of 200Hz tone have to 40 be to have the same loudness in 30 phons. dB 20 20 10 20 50 100 200 500 1000 5000 10000 FREQUENCY (HZ)P = p. g. h h= height of the liquid column in meters; p = density of liquid in =4, g = 9.8 m/'s Work Done: W = F.d F = W/d or d = W/F Gravitational Potential Energy PE = mgh or m=PE/(g.h) or h=PE/(g. m) g = 9.8 m/s? m = mass h = vertical height Kinetic Energy KE = - m v2 or m = 2 KE /vz or 1 = 2.KE v = speed or velocity Power = Energy / time or P.t = E ort = E/P Intensity = Power/ area or Intensity = Power/ 4 nr where r = distance from source n = 3.14 I = P/a or P=La or a = P/I Variation of intensity with distance r from source ly; = 12r Intensity Level (decibel dB) = Intensity I in decibels = 10 * log ( ); where Io = 10"W/m Change in decibels with change in intensity by a factor: New value in decibels is = dBy = dB, + 10 Log (factor) speed of sound in air at temperature V = 331.4 + 0.6 (T .C)