Horns · Guide
Damp a horn with stuffing
The last step fills 50 % of H1 in the tapped horn example, from the closed end, at 10,000 Pa·s/m². Inside the working band, 25–120 Hz, the response changes by at most 1.0 dB. Above 200 Hz the fill does more: the highest peak moves from 119 dB at 243 Hz to 116 dB at 301 Hz. That is the usual reason to stuff a horn: to calm the path’s resonances above the band while keeping the band itself.
Set it#
In the Horn Editor’s drawing#
- Hover a span and click its stuffing toggle to fill the whole span. Click the lit toggle again to empty it.
- Drag a flag on the bottom edge to resize the fill. Drag it past a station to carry the fill into the next span.
- Drag the stipple to slide the fill along the path.
- Click the resistivity chip to type a value, or drag it up or down. Denser dots mean a higher resistivity.
- Hover the fill for its extent, its resistivity and the band the material model fits.
In the Horn Editor’s table#
Each span row has a Stuffing cell. Stuff this span fills the whole span at 10,000 Pa·s/m², or at the resistivity of a stuffed neighbour. A stuffed span shows a chip with its resistivity and extent: click it for Resistivity in Pa·s/m², Start and End in %, and Remove stuffing.
- Airflow resistivity
- 100 to 100,000 Pa·s/m². Use the value measured for your material, or the supplier’s figure.
- Start and End
- Percentages of the span, measured from where it starts. The fill occupies the whole cross-section between them.
- Which spans
- Every path: main, rear, stub and the Paraflex auxiliary path and adapter.
- Mode spacing
- Becomes Unfilled mode spacing once a path has fill. Filled air is dispersive, so read its resonances from the response instead.
What the model assumes#
Fill uses the equivalent-fluid model from Yasushi Miki’s 1990 paper, Acoustical properties of porous materials: modifications of Delany-Bazley models. Its absorption depends on frequency and on the material’s airflow resistivity.
- The material fills the whole cross-section over its length. A lining on the walls is a different thing and is not modelled.
- Compression of the fill and turbulent flow are not modelled.
- Density is not a substitute for airflow resistivity, and there are no material presets. Measure it, or ask the supplier.
- The model fits from 1/100 of the resistivity to the resistivity itself, in hertz: 10,000 Pa·s/m² fits from 100 to 10,000 Hz. Results outside that band are extrapolated.
- Start and End follow the span, so resizing a span changes the physical length of its fill.
Check what it did#
Compare SPL, impedance and the horn diagnostics before and after. Pressure and particle velocity along the path show where the fill is working. Reading the horn diagnostics.
Stuffing and folding#
The Fold tile cannot carry stuffing onto the folded passage yet. A stuffed horn gets no folded line on the graphs, and its fold cannot be written back into the horn. Folding.
Stuffing and Hornresp#
The Hornresp export writes the fill’s resistivity and occupied length to Hornresp’s own fields, with a warning: Hornresp uses a different material model, so its response can differ. It refuses stuffing on a Paraflex auxiliary path and on a multiple-entry horn. The regression tests track stuffed cases against Hornresp without claiming agreement. Exporting to Hornresp.
Ask your AI#
Ask your AI
Using 00 Simulator, open my horn and try stuffing the first span with 10,000 Pa·s/m² fibre, filling a quarter, a half and all of it, without saving. Simulate each and tell me which calms the peaks above the working band most while changing the band itself least.
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