PyLdB

PyLdB calculates perceived loudness for pressure signatures using Stevens' Mark VII perceived loudness method. It is intended for pressure histories such as sonic boom signatures, with time in milliseconds and pressure in pounds per square foot (psf).

The main interface is the PyLdB class. A calculator can ingest arrays directly or read a two-column signature file compatible with numpy.genfromtxt. PANAIR .sig files such as misc/panair_r1.sig can be loaded by skipping the three header lines.

Quick Start

from pyldb import PyLdB

calculator = PyLdB("misc/panair_r1.sig", header_lines=3)
calculator.calculate(pad_front=6, pad_rear=6, len_window=800)

print(calculator.loudness.pldb)
print(calculator.loudness.dnl)
print(calculator.loudness.a_weighted_loudness)

After calculate() runs, results are available from calculator.loudness:

calculator.loudness.pldb
calculator.loudness.ctl
calculator.loudness.ctl_response
calculator.loudness.community_tolerance_level
calculator.loudness.dnl
calculator.loudness.equivalent_loudness
calculator.loudness.a_weighted_loudness
calculator.loudness.b_weighted_loudness
calculator.loudness.c_weighted_loudness
calculator.loudness.d_weighted_loudness
calculator.loudness.alphabet_weighted_loudnesses

Loading Data

Use PyLdB with a file:

from pyldb import PyLdB

calculator = PyLdB("signature.sig", header_lines=3)
results = calculator.calculate()

print(results.pldb)

Or pass arrays directly:

from pyldb import PyLdB

calculator = PyLdB(time=time_ms, pressure=pressure_psf)
results = calculator.calculate(pad_front=10, pad_rear=10)

The input arrays must be one-dimensional, equal length, strictly increasing in time, and evenly sampled.

Acoustic Metrics

calculate() computes PLdB first, then uses the acoustic helper methods to populate additional metrics:

• pldb: Stevens Mark VII perceived loudness in PLdB.
• ctl: Fidell CTL high-annoyance response probability for the supplied community tolerance level.
• community_tolerance_level: CTL value used for the response calculation.
• dnl: day-night average level. If no day or night levels are supplied, PLdB is used as the representative level for all 24 hours.
• equivalent_loudness: energy-equivalent level. If no sequence is supplied, PLdB is used.
• alphabet_weighted_loudnesses: A-, B-, C-, and D-weighted overall levels calculated from the one-third-octave band sound pressure levels.

Optional inputs:

results = calculator.calculate(
    ctl=75.0,
    growth=0.3,
    day_loudness=[70.0] * 15,
    night_loudness=[60.0] * 9,
    equivalent_loudnesses=[72.0, 75.0, 71.0],
)

Legacy API

Function-style calls are still available for compatibility:

import pyldb

time, pressure = pyldb.import_sig("misc/panair_r1.sig", header_lines=3)
pldb = pyldb.perceivedloudness(time, pressure, pad_front=6, pad_rear=6)

New code should prefer the PyLdB class because it exposes the full result set through calculator.loudness.

Installation

Clone the repository and install it in your Python environment:

git clone https://github.com/usuaero/PyLdB.git
cd PyLdB
pip install -e .

Testing

Unit tests are implemented with pytest:

pytest verif/test.py

Notes

PyLdB was supported by the NASA University Leadership Initiative (ULI) program under federal award number NNX17AJ96A, titled Adaptive Aerostructures for Revolutionary Civil Supersonic Transportation.

Support

Contact doug.hunsaker@usu.edu or christianrbolander@gmail.com with questions.

License

This project is licensed under the MIT license. See LICENSE for details.