Theory
Sullivan & Crocker measured the impedance of one perforate (hole diameter 2.49 mm, plate 0.81 mm) without flow. They found a frequency-independent resistance of about 2.4 kg m⁻² s⁻¹ in the linear regime and a reactance fitted by an end correction of (Sullivan and Crocker, 1978). The program keeps the reactance law and takes the resistance from this field, normalised by of the local gas, equation (1). The wall impedance is then (Acoustic impedance model of a perforated wall).
Equations
| where | meaning | unit |
|---|---|---|
| Single-hole resistance (this field) | kg m⁻² s⁻¹ | |
| Density and speed of sound of the local gas | kg/m³, m/s | |
| Wavenumber | 1/m | |
| Wall thickness and hole diameter | m |
Default and rule
- Default
- 2.4 rayl (kg m⁻² s⁻¹)Measured
- Rule
2.4 rayl, the paper's measured value for its perforate. Enter a measurement of your own for another perforate.
- Source
(Sullivan and Crocker, 1978), section III.A and Fig. 5.
Valid range > 0
Values
Above 0.
Legacy model
The model has no flow dependence and the value belongs to one plate; it is offered only to walls that already use it. The Elnady model covers this case.