1. What is Spherical Spreading Attenuation?

Spherical spreading attenuation describes how sound energy decreases as it propagates outward from a point source in a free field. The sound intensity follows the inverse square law, resulting in 6 dB attenuation per doubling of distance.

2. How Does the Calculator Work?

The calculator uses the spherical spreading equation:

Where:

• \( \Delta L \) — Noise attenuation in decibels (dB)
• \( r_2 \) — Distance 2 from the sound source (meters)
• \( r_1 \) — Distance 1 from the sound source (meters)

Explanation: The equation calculates the sound level difference between two distances from a point source, assuming spherical wave propagation in a free field.

3. Importance of Noise Attenuation Calculation

Details: Accurate noise attenuation prediction is crucial for environmental noise assessment, industrial noise control, architectural acoustics, and noise impact studies.

4. Using the Calculator

Tips: Enter both distances in meters. Distance values must be positive numbers. The calculator assumes a point source in free field conditions.

5. Frequently Asked Questions (FAQ)

Q1: Why 20 log instead of 10 log?
A: Sound pressure level uses 20 log because it's proportional to pressure (amplitude), not intensity (power). The 20 log relationship gives the correct 6 dB per doubling of distance.

Q2: What are typical attenuation values?
A: For every doubling of distance, sound level decreases by approximately 6 dB. For every tenfold increase in distance, sound level decreases by 20 dB.

Q3: When does spherical spreading apply?
A: Spherical spreading applies to point sources in free field conditions without reflections, absorption, or other interfering factors.

Q4: What are the limitations of this model?
A: This model doesn't account for atmospheric absorption, ground effects, reflections, wind, temperature gradients, or source directivity.

Q5: How does this differ from line source attenuation?
A: Line sources (like traffic on a road) follow cylindrical spreading with 3 dB attenuation per doubling of distance, unlike the 6 dB for point sources.