NCIDQ IDFX Practice Exam

To achieve a noticeable reduction in noise by 5dB, how much must the total absorption be increased?

1. By at least 1 time

2. By at least 2 times

3. By at least 3 times

4. By at least 4 times

The correct answer is: By at least 3 times

To achieve a noticeable reduction in noise of 5dB, it is important to understand the relationship between sound absorption and the decibel scale. The decibel scale is logarithmic, which means that an increase in sound absorption doesn't linearly correlate with a decrease in perceived noise levels. In terms of absorption coefficients, to achieve a reduction of 5dB, the total sound absorption must be increased substantially. Specifically, a 5dB reduction means that the overall sound energy needs to be halved, which mathematically corresponds to increasing the absorption by about three times in total absorption. This is because each 3dB change represents a doubling or halving of sound intensity, thus increasing the absorption substantially is necessary to achieve the desired reduction in decibels. Therefore, to reduce noise levels significantly, the increase in total absorption must be approximately three times the original level, aligning with acoustic principles and practices in sound management.