UGC NET Questions (Paper – 1)

Noise pollution refers to unwanted or harmful sound in the environment. Sound intensity is measured on a logarithmic scale called the decibel scale. Environmental and occupational standards specify safe limits in decibels for different settings. Therefore, decibel (dB) is the correct unit used for noise levels.

Option A:
Option A is incorrect because parts per million are used for concentrations of gases or solutes, not for sound. Air pollutants like SO₂ or NO₂ may be reported in ppm.

Option B:
Option B is correct as decibel is the standard unit for sound intensity. It allows comparison of noise levels from different sources on a common scale.

Option C:
Option C is incorrect since hertz measures frequency, not loudness. Frequency describes pitch, while decibels indicate intensity.

Option D:
Option D is incorrect because lumen is a unit of luminous flux used in lighting, not sound. It is relevant to visual, not auditory, pollution.

Noise intensity is typically measured using the decibel scale,which is logarithmic and reflects the perceived loudness of sound. Environmental regulations often specify acceptable noise levels in decibels for different zones. Therefore decibel is the correct unit mentioned in the stem.

Option A:
Candela is a unit of luminous intensity used in photometry to measure light,not sound. It has no direct relation to noise measurement,so it cannot fill the blank correctly.

Option B:
Decibels provide a convenient way to express very large ranges of sound power in manageable numbers. Because the question specifically refers to environmental noise measurement,this option precisely matches the standard practice.

Option C:
Watt hour is a unit of energy,commonly used for electricity consumption. It does not describe sound intensity or noise levels. Hence it is not relevant to the concept in the question.

Option D:
Lumen measures luminous flux or the total amount of visible light emitted by a source. It is again related to light rather than sound,so it is not appropriate for the blank.