Sound power emitted is the total amount of acoustic energy radiated by a sound source per unit of time. It is a fundamental characteristic of sound sources and is measured in watts (W). Unlike sound intensity, which varies with distance from the source, sound power is a constant property of the source itself.
Formula
The formula for sound power emitted is:
\[ P = I \times A \]
Where:
\( P \) is the sound power emitted (in watts, W)
\( I \) is the sound intensity (in watts per square meter, W/m²)
\( A \) is the surface area (in square meters, m²)
Calculation Steps
Let's calculate the sound power emitted for a given scenario:
Given:
Sound Intensity (\( I \)) = 0.5 W/m²
Surface Area (\( A \)) = 10 m²
Apply the sound power formula:
\[ P = I \times A \]
Substitute the known values:
\[ P = 0.5 \text{ W/m²} \times 10 \text{ m²} \]
Perform the final calculation:
\[ P = 5 \text{ W} \]
Example and Visual Representation
Let's visualize the concept of sound power emitted:
This diagram illustrates:
The sound source (yellow circle) emitting sound power (\( P \))
The sound intensity (\( I \)) represented by the green arrow
The surface area (\( A \)) through which the sound passes (blue circles)
The decreasing intensity as the sound spreads over a larger area (fading blue circles)
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