[aguirreSL]

Adds two modules for absorption, as ita_sabine and ita_reverberation_chamber_absorption_coefficient in the ITA-Toolbox:

1. pytta.iso9613.attenuation(f, temperature, humidity, pressure): pure-tone attenuation of sound by the atmosphere in dB/m, ISO 9613-1. The humidity enters through the molar concentration of water vapour, from the saturation pressure of the standard.
2. pytta.iso354, measurement of sound absorption in a reverberation room, ISO 354:2003:
   • absorption_area(T, V, c, m=0): Equations (5) and (7), A = 55.3 V / (c T) - 4 V m;
   • absorption_coefficient(T1, T2, V, S, t1, t2, m1, m2): Equations (8) and (9), with the speed of sound of each measurement from Equation (6);
   • power_attenuation(f, temperature, humidity, pressure): m = alpha / (10 lg e), with alpha from ISO 9613-1, as the standard asks;
   • sabine(V, A, c, m=0) and eyring(V, S, alpha, c, m=0): reverberation times.

The tests in tests/test_iso354.py:

1. Check the air absorption against the ISO 9613-1 table for 20 °C (relative humidity 20 %, 50 % and 100 %, 63 Hz to 8 kHz), as reproduced in Long, Architectural Acoustics, Table 5.1. The largest relative deviation is 0.24 %, within the three significant digits of the table.
2. Build a room of 200 m³ with Sabine, add 10 m² of a material with alpha = 0.6, and get alpha back from Equations (5) to (9), with air absorption at 500 Hz and 4 kHz.
3. Check that T_Eyring / T_Sabine = alpha / -ln(1 - alpha) for the same mean absorption.

Checked with Python 3.12, numpy 1.26 and scipy 1.17. The existing tests behave as on development: the 7 failures there (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