AcouVApp Field

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_ptotal):

• 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.