Module 3: Spatial Fields & Environments

Free Field vs. Diffuse Field

The acoustic extremes of boundless space vs. endless reflections. Explore how sound propagates in anechoic chambers with zero echo vs. reverberation rooms where omnidirectionally integrated sound fields bounce indefinitely.

Interactive Acoustic Soundstage Guide

1. Toggle Space Profiles

Use the console switch button track to jump instantly between an absorbing Free Field and a reflective Diffuse Field.

2. Manipulate Metrics

Slide the physical source power and distance vectors to map localized sound pressure level attenuation limits across coordinates.

3. Analyze Field Energy

Observe the cross-sectional graph below the stage tracking real-time drop-off values versus isotropic environment equilibrium levels.

Acoustic Boundary Interaction Engine

Simulate environment boundaries. Toggle between a perfectly absorbing Free Field (Anechoic) and a highly reflective Diffuse Field (Reverberant) to track sound vector scattering profiles.

Acoustic Space Mode
Boundary Reflection Ray Map
Source Direct Ray Scattered Vectors
Spatial Energy Distribution Profile
Lines Analysis Guide

Loading spatial field calculations...

Absorption Coefficient (α)
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Boundary dampening conversion metric
Net Received Level (SPL)
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Total raw pressure summation at listener
Sound Field Property
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Isotropic density vs free attenuation tracking

The Layman Breakdown: Endless Horizons vs. The Mirror Maze

What happens to acoustic energy once it leaves a source? Depending on environmental boundary properties, sound either travels infinitely into oblivion or compiles into a uniform, dense soup.


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The Boundless Free Field

Imagine suspended speakers hanging perfectly in the open air, miles above the earth. When sound leaves the driver cones, it keeps traveling outward forever, never hitting a wall, tree, or floor. There are zero acoustic reflections.

Because no energy ever returns to your ears, volume drop-off obeys pure inverse-square physics. It sounds exceptionally dry, clinical, and eerie because your brain receives no environmental feedback.

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The Blended Diffuse Field

Now imagine a heavy concrete vault with high-gloss marble barriers and zero furniture. When you clap your hands, the sound waves strike the walls and bounce off with almost zero loss of energy. Within milliseconds, millions of reflections cross lines.

The space fills with an isotropic sound field—meaning acoustic energy becomes completely uniform. Moving around the room does not change the volume because the reflections blend together into a dense, non-directional soup.

Acoustic Proof

Energy Density Integration & Reverberant Room Sabins

In a perfect free field, the sound pressure level attenuation calculation drops off cleanly based strictly on radial geometry distance ($r$):

$$SPL_{\text{free}} = L_w - 20\log_{10}(r) - 11$$

In a perfect diffuse field, total energy density ($E$) stabilizes as a function of room volume ($V$) and the average absorption coefficient ($\\alpha$) of bounding elements. Sound level depends entirely on the reverberant steady state rather than distance:

$$E = \frac{4 W}{c A \alpha} \quad \text{where} \quad A \alpha = \sum S_i \alpha_i \quad \text{(Total Sabins)}$$
Absorption ($\alpha$)
Dampening Value: A metric from 0.0 (total reflection, perfect concrete diffuse criteria) to 1.0 (total absorption, an echoic open horizon free field).
Isotropic State
Uniform Spread: The ultimate goal of a diffuse chamber. At any spatial coordinate, the probability of wave vectors entering from any random structural angle matches identically.