## How to Calculate Diffuse and Direct Sound Levels from Acoustic Power

This calculation helps estimate the **diffuse and direct sound levels** from the
**acoustic power level of a source**. It is crucial in determining the overall noise
environment of a room or space.

### Formula for Calculating Total Sound Pressure Level (L_{p}total):

\[
Lp_{total} = L_{w} + 10 \log_{10} \left( \frac{Q}{4 \times \pi \times r²} + \frac{4}{R}\right)
\]

**R** is called the room constant and is calculated using the formula:
\[
R = \frac{S \times \alpha_{mean}}{1 - \alpha_{mean}}
\]

### Conditions Indicating a Non-Diffuse Field:

This calculation is valid in a **diffuse field condition**, where sound is evenly
distributed. It does not account for the **modal aspect** of the room, which is a factor at
frequencies below the Schroeder frequency.

A sound field is considered non-diffuse when one or more of the following conditions are met:

- Uneven distribution of sound absorption on surfaces, such as when only one surface is highly
absorbing
- Lack of sound diffusing or scattering elements, like furniture, in the room
- Room dimensions where the ratio of longest to shortest room dimensions is higher than three
- Very large volumes, typically over 5000m³

### Schroeder Frequency Calculation:

The **Schroeder Frequency (f**_{s}) is calculated using the formula:

\[
f_{s} = 2000 \times \sqrt{\frac{T}{V}}
\]

Where:

**T** is the *reverberation time* (mean across all frequency ranges)
**V** is the *volume* of the space

For further reading, see: *Engineering Noise Control - Theory and Practice - Bies*.

Learn more about room modes or explore our acoustic product
database.