Why? Because a quarter wavelength from your wall, the total travel difference (for a wave reflecting back on itself) is half a wavelength. Shortly after the reflection in this animation, the direct and reflected waves are superimposed and a standing wave is formed.Ĭancellation always occurs at ¼ the wavelength from your wall, regardless of the phase of the wave hitting the wall. If you place your speaker on an antinode, it will cause a peak or boost in the frequency response at 60 Hz. If you place your speaker on a node, it will cause a null or dip in the frequency response at 60 Hz.ġ/2 wavelength from the wall is an anti-node, where the two waves have added together (constructive interference). The animation shows them as equal strength, which does not actually happen in your room… but your bass reflections are still strong enough to cause serious problems! The amount of cancellation depends on the strength of the reflection relative to the direct sound. These are the places where the direct and reflected sound are always cancelling each other out (destructive interference).
After reflection, the sound pressure (charted amplitude) is zero at 1/4, 3/4, 5/4, etc wavelength from the boundary (the points in the wave that don’t move). Courtesy of Dan Russell at Penn State University. This causes a horrid dip, notch or null in the frequency response.Īnimation of a sound wave reflecting off a boundary. If your speaker is one quarter wavelength from the wall for a certain frequency, wave cancellation occurs at that frequency. When the reflected sound wave bouncing off your wall combines with the source sound wave coming from your speaker, it creates acoustic interference. Bass waves radiate backward from your speakers, toward the wall in front of you… and when they hit the wall, they reflect. Speakers are more omnidirectional at low frequencies, meaning bass waves radiate in all directions, causing a rumbling ruckus. Not hearing enough bass through your monitors? The distance between your room boundaries and speakers has a huge impact on your bass performance. For the axisymmetric scattering from a circular disc, a highly effective symmetric formulation results, and results agree with reference solutions across the entire frequency range.Speaker Placement and Reflections from Nearby Walls Is Speaker-Boundary Interference Killing Your Bass? PART: 1 2 3 4 No problems with irregular frequencies, as happen with the Kirchhoff–Helmholtz integral equation, are observed for this formulation. Numerical experiments demonstrate accurate response for frequencies down to 0 for thin plates and a cube.
In a subsequent step, this edge source signal is propagated to yield a multiple-order diffracted field, taking all diffraction orders into account.
This gives what can be called an edge source signal. It is shown that the multiple-order diffraction component can be found via the solution to an integral equation formulated on pairs of edge points. An existing secondary-source model for edge diffraction from finite edges is extended to handle multiple diffraction of all orders. The formulation is based on decomposing the field into geometrical acoustics, first-order, and multiple-order edge diffraction components. A formulation of the problem of scattering from obstacles with edges is presented.