Question

To have a good sound effect inside a hall

• A. the hall should not have any sound absorbing material
• B. the reverberation time has to be maximum
• C. the reverberation time has to be zero
• D. the reverberation time has to be optimum

Hint:

The Sabine formula, $T = \frac{0.161 V}{A}$, is used by engineers to calculate reverberation time, where $V$ is volume and $A$ is total absorption. Adjusting "A" with carpets or curtains is how the "optimum" time is achieved.

Answer 1

The Correct Option is D

1. What is Reverberation Time?: Reverberation time is the time taken for the sound intensity to drop by $60 \text{ dB}$ after the source has stopped.

2. Why extremes are bad:

• Too high (Maximum): Sound persists for too long, causing overlapping of syllables and making speech unintelligible (excessive echoes).

• Too low (Zero): The hall feels "dead." Sound lacks richness and fails to reach the back of the room effectively.

3. The "Optimum" Requirement: A "good sound effect" requires a balance. Speech requires shorter reverberation times ($\approx 0.5 \text{--} 1.0 \text{ s}$) for clarity, while music requires slightly longer times ($\approx 1.5 \text{--} 2.0 \text{ s}$) for a full, resonant quality. Therefore, designers aim for an

optimum time based on the hall's purpose.