imptube

This library provides an implementation of transfer function impedance tube measurements according to ISO 10534-2:1998.

It requires several Python packages to be installed:

• sounddevice
• soundfile
• scipy
• numpy
• pandas

Installation

It is currently not possible to install this library using pip or conda, please use the latest released package instead and install using pip locally.

Documentation

Documentation can be found here

Usage

The library currently provides two ways to perform a measurement.

Method 1: Direct measurement without saving any data

This method shows the inner logic of the whole measurement. In contrast to the second method, this method does not work with any folder/file structure.

import imptube as imp

temp = 29  # Temperature in degrees Celsius
humidity = 30  # Relative humidity in percent
atm_pressure = 101300  # Atmospheric pressure in Pascal

tube = imp.Tube(
    further_mic_dist=0.4,
    closer_mic_dist=0.1,
    freq_limit=1000
)

measurement = imp.Measurement(device=15)  # Create an instance of the Measurement class

# Perform the configuration 1 measurement
data, fs = measurement.measure(export=False, thd_filter=True)  
p11, p12 = imp.stereo_to_spectra(data.T)
freqs = imp.frequencies(p11, fs)

input("Ready to measure in the second configuration?") 

# Perform the configuration 2 measurement
data, fs = measurement.measure(export=False, thd_filter=True)
p21, p22 = imp.stereo_to_spectra(data.T)

# Calculate the calibration factor based on the spectra
cf = imp.calibration_factor(p11, p12, p21, p22)
# Calculate the transfer function based on the spectra
# of the first configuration
tf = imp.transfer_function(p11, p12)  

# Correct the transfer function using the calibration factor
tf_corrected = tf / cf  
tf_I, tf_R = imp.tf_i_r(temp, freqs, tube.mic_spacing)

# Calculate the reflection factor, absorption coefficient and 
# surface impedance based on the transfer function and other parameters
refl_factor = imp.reflection_factor(tf_I, tf_R, tf_corrected, temp, freqs, tube.closer_mic_dist)  

absorption_coeff = imp.absorption_coefficient(refl_factor)

surf_impedance = imp.surface_impedance(refl_factor, temp, atm_pressure)

Method 2: Using the Sample class and autosaving the captured and processed data to a specific folder structure

import imptube as imp

tube = imp.Tube(
    further_mic_dist=0.3,
    closer_mic_dist=0.1,
    freq_limit=1000)

measurement = imp.Measurement(device=15)

sample = imp.Sample("test1",
    temperature=29,
    rel_humidity=30,
    tube=tube)

imp.calibration(
    sample=sample,
    measurement=measurement
)

imp.single_measurement(
    sample=sample,
    measurement=measurement,
    depth=160
)

Acknowledgments

This library was created thanks to the FAST-J-22-7880 project.

Special thanks to Prof. Christ Glorieux for his help with the theory.

Github Copilot was used to generate parts of the documentation and code.

Author

• David Jun

  PhD student at Brno University of Technology and KU Leuven

Contributing

Pull requests are welcome. For any changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

License

MIT