# Horn Pressure

> Inspect RMS pressure and phase at stations inside a horn, distinguish internal pressure from listening SPL, and interpret pressure peaks with flow.

Source: https://simulator.00aud.io/docs/reference/tiles/horn-pressure

Horn Pressure reads the acoustic pressure inside the horn at the station you choose. Use it to locate pressure build-up and understand how the path loads the driver.

- **Shows:** RMS acoustic pressure in Pa, or its phase, at a chosen station inside the horn.
- **Healthy when:** The station and mode are the ones you mean; a pressure peak is interpreted alongside flow and SPL.
- **If it is not:** Compare another station and inspect particle velocity before changing geometry.

## The tile

_Figure: Horn Pressure at Main H1 throat, Main H2 mouth, Main H4 mouth in the tapped-horn example._

Tapped-horn example at 100 W, half space, 1 m. Stations are measured from the closed end. Simulated when this page was built.

| Station | Position | Area | Peak | At |
| --- | --- | --- | --- | --- |
| Main H1 throat | 0.00 m | 400 cm² | 1,485.42 Pa RMS | 40.2 Hz |
| Main H2 mouth | 0.95 m | 600 cm² | 1,130.97 Pa RMS | 41.2 Hz |
| Main H4 mouth | 2.50 m | 2,400 cm² | 178.68 Pa RMS | 93.1 Hz |

In the tapped-horn example the closed-end station peaks at 1,485.4 Pa RMS, while the mouth peaks at 178.7 Pa RMS. Those maxima occur at different frequencies. [Open the example](https://simulator.00aud.io/app?template=tapped-horn&power=100) and compare stations at the same frequency with the hover readout.

Choose a location above the plot. The initial location is the first span’s throat. **Magnitude** shows Pa RMS; **Phase** shows pressure phase relative to the electrical drive. This is local pressure, not the SPL at the listening position.

## High pressure need not mean fast air

A closed end can support a large pressure variation while its volume flow is essentially zero. At other stations a narrow passage can have much more air motion. Read **Horn Particle Velocity** at the same location before drawing conclusions about air speed.

| Change or observation | Interpretation |
| --- | --- |
| More input power | Pressure rises with drive amplitude in the linear model. |
| Choose another station | The reading changes location; the horn itself is unchanged. |
| Change length, flare or stuffing | Changes resonances and acoustic loading; check SPL and excursion as well. |
| A comparison enclosure has no matching station | Its curve is left out; it is not a zero-pressure result. |

> **No pressure pass or fail line** The tile has no structural pressure rating and does not predict panel vibration, turbulence or nonlinear distortion. It describes the linear acoustic field inside the model.

## What to try

| Try | What it changes |
| --- | --- |
| [Choose a station](https://simulator.00aud.io/docs/horns/diagnostics#locations) | Compare the throat, a constriction and the mouth; the default is the first span’s throat. |
| [Compare pressure with flow](https://simulator.00aud.io/docs/reference/tiles/horn-particle-velocity) | High pressure can occur where flow is small. Read **Horn Particle Velocity** at the same station. |

## Ask your AI

**Ask your AI**

> Using 00 Simulator, simulate my horn at its current power and compare pressure and particle velocity at the throat, a narrow station and the mouth. Explain the largest pressure peak and identify its frequency without treating it as listening SPL.