Question

The unit used to measure sound intensity level is:

• A. Hertz
• B. Decibel
• C. Pascal
• D. Joule

Hint:

Always remember: {Sound intensity level = Decibel (dB)} and {Frequency = Hertz (Hz)}.

Answer 1

The Correct Option is B

Step 1: Understanding sound intensity and sound intensity level.
Sound intensity is defined as the sound power transmitted per unit area perpendicular to the direction of sound propagation. However, the human ear cannot perceive sound intensity on a linear scale; instead, it responds logarithmically to changes in sound intensity. Therefore, sound intensity is expressed in terms of \textit{sound intensity level}.
Step 2: Definition of sound intensity level.
Sound intensity level is a logarithmic measure of sound intensity relative to a reference intensity. It is given by the formula: \[ L = 10 \log_{10} \left( \frac{I}{I_0} \right) \] where \( I \) is the sound intensity and \( I_0 \) is the reference sound intensity. The unit of sound intensity level is the decibel (dB).
Step 3: Reason for using decibel scale.
The decibel scale compresses a very wide range of sound intensities into a manageable scale. This makes it suitable for representing noise levels in environmental studies and noise pollution assessment.
Step 4: Analysis of options.
(A) Hertz: Hertz is the unit of frequency and measures the pitch of sound, not intensity level.
(B) Decibel: Correct — Decibel is the standard unit used to measure sound intensity level on a logarithmic scale.
(C) Pascal: Pascal is the unit of pressure and is used to measure sound pressure, not sound intensity level.
(D) Joule: Joule is the unit of energy and has no direct relation to sound intensity level.
Step 5: Final conclusion.
Since sound intensity level is expressed on a logarithmic scale and measured in decibels, the correct answer is (B) Decibel.