[aguirreSL]

Adds pytta.absorbers: the surface impedance and absorption of layered absorbers by the transfer matrix method, as the Impedance Calculator of the ITA-Toolbox (applications/Analytic/Impedance_Calculator).

1. porous(f, sigma, model='miki'): the characteristic impedance and wavenumber of a porous material of flow resistivity σ, by the empirical models of Delany and Bazley (1970), Miki (1990, with the constants of the paper, Eqs. (27) and (28)) or Komatsu (2008, valid up to f / σ = 100, where it reaches air).
2. mpp_impedance(f, diameter, thickness, porosity): the series impedance of a microperforated panel by Maa (1998).
3. surface_impedance(f, layers, angle=0): the surface impedance of layers on a rigid backing, given from the surface down as ('air', d), ('porous', model, sigma, d), ('mpp', diameter, thickness, porosity) or ('mass', m). At oblique incidence the air and porous layers keep the trace wavenumber, while the panels react locally.
4. absorption(Zs, angle=0) and random_incidence_absorption(f, layers=None, Zs=None): the absorption coefficient at an angle and Paris' integral over the angles of incidence.

The Komatsu model and the 1D transmission line were checked against Aretz (2012), Eqs. (7.12) to (7.15), and the Miki constants against the paper, both from my library. The ITA calculator also has the Attenborough model, permeable mass layers and bending plates, after Mechel's Formulas of Acoustics, which are not included.

The tests in tests/test_absorbers.py print the measured differences:

1. A rigid-backed air layer has Zs = -j ρc cot(kd) (5.5e-16) and absorbs nothing.
2. The transfer matrix of one porous layer gives Zc coth(Γd) (2.3e-16), and a 5 m layer gives Zc.
3. Delany-Bazley and Miki tend to air at large f / σ, and Komatsu reaches air at f / σ = 100. The Miki model agrees with its usual rounded SI form (0.0699, 0.107, 0.109, 0.160) within that rounding.
4. As ω goes to 0, the microperforated panel tends to the Poiseuille resistance 32ηt / (p d²) and to the mass ρt (4/3 + 0.85 d/t) / p.
5. For a locally reacting surface with a real normalized impedance z, Paris' integral equals 8/z (1 + 1/(1 + z) - (2/z) ln(1 + z)) within 1e-5, for z from 0.5 to 10.
6. Unknown models and layers are rejected.

Checked with Python 3.12, numpy 1.26 and scipy 1.17. The 7 failures of development (3 in test_h5io.py, 4 in test_pyttasave.py) are the same with and without this change.

Co-Authored-By: Claude Fable 5.1 noreply@anthropic.com