b2KIT

Doppler Effect Simulator

Visualize wavefronts from moving sources. Adjust source speed and see frequency shift, Mach cones, and sonic booms.

Tested tool guide Tested browser tools Checked August 16, 2026

What Doppler Effect Simulator does and how it behaves

Follow successive wavefronts as an emitting source moves through its propagation medium. Adjusting the source speed shows compressed fronts ahead, expanded fronts behind, and the transition from ordinary Doppler shift to a Mach cone and sonic boom. The common misreading is that closely packed fronts mean the source itself is emitting more frequently. The emission rate can remain constant; source motion changes the spacing between fronts and therefore the rate at which they reach a stationary observer.

How the result is produced

1

Moving emission centers

Each wavefront begins at the source position where that crest was emitted, then expands at the wave speed while the source continues moving. Consequently, successive centers do not coincide. Fronts are closer together in the direction of motion and farther apart behind the source, representing shorter and longer observed wavelengths respectively.

2

Supersonic transition

When the source reaches the wave speed, forward disturbances accumulate instead of moving ahead of it. Above that speed, overlapping wavefronts have a common envelope: a Mach cone, shown in a two-dimensional view as a V shape. For Mach number M greater than 1, its half-angle satisfies sin(mu) = 1/M.

Good uses

  • Compare the wavefront pattern in front of and behind a moving sound source.
  • Demonstrate why an approaching source is heard at a higher frequency and a receding source at a lower frequency.
  • Explore how the Mach cone narrows as a source moves farther above the wave speed.

Limits and checks

  • Do not interpret the animation speed or pixel spacing as measured physical units unless the simulator explicitly supplies a scale.
  • A sonic boom is heard when a supersonic source's shock front passes an observer, not only at the instant the source first exceeds the sound speed.
  • The Mach regime depends on source speed relative to the local wave speed. Source speed by itself is insufficient when the medium or conditions differ.

Common questions

Does source motion change the frequency being emitted?

No, not necessarily. A source may emit crests at a constant rate in its own frame while its motion changes the distance between successive wavefronts. A stationary observer then encounters compressed fronts more often as the source approaches and expanded fronts less often after it passes.

Can this simulation be used for the Doppler shift of light?

No, not as a quantitative light-frequency calculator. The moving-source wavefront construction describes waves propagating through a medium and supports sound-speed concepts such as Mach cones and sonic booms. Light in vacuum requires the relativistic Doppler relation, which does not use a source speed relative to a propagation medium.

References and verification

The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.

Related Tools