A point source of sound has a power of 17 W - AQA - A-Level Physics - Question 3 - 2021 - Paper 5

Next, calculate the intensity (I) of the sound using the formula:

$I = \frac{P}{A}$

Where P is the power (17 W) and A is the area calculated:

$I = \frac{17}{452.39} \approx 0.0376 \text{ W/m}^2$

Finally, calculate the intensity level in decibels (dB) using the formula:

$L = 10 \log_{10}\left( \frac{I}{I_0} \right)$

where $I_0 = 10^{-12} \text{ W/m}^2$ (reference intensity). Thus:

$L = 10 \log_{10}\left( \frac{0.0376}{10^{-12}} \right) \approx 10 \log_{10}(3.76 \times 10^{10}) \approx 10 \times 10.576 \approx 105.76 ext{ dB}$

As the frequency is increased from 3.0 kHz to 8.0 kHz, one other change perceived by a person is that the sound may become quieter at higher frequencies. This phenomenon occurs because human hearing sensitivity varies with frequency, often being less sensitive as frequency increases.