Learning Forum

[ankit.ghosh]

A noise analysis is to be conducted within the engine room of a small craft, where the air inside the engine room is modeled using solid elements for a purely acoustic analysis. Given that the room is enclosed by steel, an impedance boundary condition is applied to all exposed surfaces. In order to define an impedance boundary in ANSYS, both resistive and reactive components are required. However, there are no suitable resources available to calculate these components. The calculations we have conducted are based on the fundamental principles of acoustic theory. Could you kindly verify and correct them?

Also, guide on " How can I verify and validate the results of my acoustic analysis? Are there any resources available to help perform hand calculations?"

 

Medium 1 - air
Density of air	ρa	1.225	kg/m3
Speed of sound in air	Ca	330	m/s
Impedance of Air	Za = ρa * Ca	404.25	kg/m2s
Medium 2 - steel
Density of steel	ρs	7750	kg/m3
Speed of sound in steel	Cs	5000	m/s
Impedance of steel	Zs = ρ* Cs	38750000	kg/m2s
Absorption coefficient	α	0.66		For steel
Reflection	R	0.9999
Transmission	T	4.17282E-05
Resistive Component	Zr = Zs / α	58712121.21	kg/m2s
		58.712	kg/mm2s
Reactive Component	Za	404.25	kg/m2s
		0.00040425	kg/mm2s

 

[Federico]

Hello, 

results shown in yellow appear correct to me, except Transmission which differs by a factor of 2 from my results 
Z = rho*c

R = (Z1-Z2)/(Z1+Z2)

T = 2Z1/(Z1+Z2)