31. What will be the resultant decibel level when two sources make noise of equal decibels?

- Decibel level will be the same
- Decibel level will increase by 3 decibels
- Decibel level will decrease by 3 decibels
- Decibel level will be equal to the sum of decibels of the two sources

32. The equivalent noise level is significant for the following

- Fluctuating noise over different time periods
- Fluctuating noise over constant time periods
- Constant noise over different time period
- Constant noise over same time periods

33. In a sinusoidal wave of the sound pressure, the number of times a peak amplitude arrives in one second is called as

- wavelength
- amplitude
- period
- none of these

34. The following statement is true between Period (P) and frequency (f) of a sound wave?

- P is inversely proportional to f
- P is linearly proportional to f
- P is directly proportional to the square of f
- P is directly proportional to f

35. Acceptable noise level for residential and business urban areas as per IS 4854 – 1968 is

- 25-35 dB
- 40 -50 dB
- 50 – 60 dB
- 70 -80 dB

36. Human beings are most sensitive to sound oscillations with frequencies between

- 100-1000 cycles/sec
- 200-2000 cycles/sec
- 300-3000 cycles/sec
- 400-4000 cycles/sec

37. An industry is having two machines each will generate 70 dB noise. If both the machine are operated simultaneously, what will be the total noise generated from the machines?

- 70 dB
- 73 dB
- 140 dB
- 4900 dB

38. A source emitting 80 dB and another emitting 60 dB if put in the same location will produce a noise of

- 80 dB
- 140 dB
- 60 dB
- 20 dB

39. The threshold of hearing for normal healthy ear is

- 0.00002 N/m
^{2} - 0.0002 N/m
^{2} - 0.002 N/m
^{2} - 0.02 N/m
^{2}

40. The degree of hearing loss depends on the

- intensity of the noise
- Duration of the noise

- Statement (ii) alone is true
- Statement (i) alone is true
- Both the statements are false
- Statement (i) or (ii) are true