[aguirreSL]

Adds the module pytta.iso3382 with two spatial measures of ISO 3382-1:2009 that RoomAnalysis does not have:

1. lateral_fraction(omni, eight, nthOct=1, minFreq=125, maxFreq=4000) gives the early lateral energy fractions JLF (A.14) and JLFC (A.15) from the impulse responses of an omnidirectional and a figure-of-eight microphone at the same point. JLF sums pL² and JLFC sums pL·p from 5 ms to 80 ms, both over the sum of p² from 0 to 80 ms.
2. iacc(binaural, t1=0, t2=None, nthOct=1, minFreq=125, maxFreq=4000) gives the interaural cross correlation coefficient (B.1, B.2): the largest magnitude of the normalized cross correlation of the left and right ear responses over t1 to t2, for lags shorter than 1 ms. t1=0, t2=0.08 gives the early IACC and t1=0.08 the late one.

Both work by octave or fractional octave band through OctFilter, or broadband with nthOct=None. The time origin is the start of the impulse response, the first sample whose squared value is within 20 dB of the maximum, found on the broadband responses and kept for every band. The late lateral sound level LJ (A.16) is not included, since it needs the response of the source at 10 m in a free field.

The tests in tests/test_iso3382_spatial.py build responses from single reflections, so the expected values are exact:

1. With lateral reflections at 3 ms, 20 ms, 40 ms (60° off the lateral axis) and 100 ms, JLF and JLFC match A.14 and A.15. This pins the 5 ms and 80 ms limits and the cosine against the squared cosine.
2. Silence before the direct sound does not change the fractions.
3. IACC is 1 for identical ears, for inverted ears and for ears 0.5 ms apart, and 0 for ears 2 ms apart.
4. Identical early parts with late parts 3 ms apart give an early IACC of 1 and a late IACC of 0.
5. Band analysis returns one value per octave from 125 Hz to 4 kHz.

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