Removed lasp_imptube. Old code not of use anymore
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#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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"""!
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Author: J.A. de Jong - ASCEE
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Description: Two-microphone impedance tube methods
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"""
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__all__ = ['TwoMicImpedanceTube']
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# from lrftubes import Air
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from .lasp_measurement import Measurement
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from numpy import pi, sqrt, exp
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import numpy as np
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from scipy.interpolate import UnivariateSpline
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# from lrftubes import PrsDuct
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from functools import lru_cache
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class TwoMicImpedanceTube:
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def __init__(self, mnormal: Measurement,
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mswitched: Measurement,
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s: float,
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d1: float,
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d2: float,
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fl: float = None,
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fu: float = None,
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periodic_method=False,
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# mat= Air(),
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D_imptube = 50e-3,
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thermoviscous = True,
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**kwargs):
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"""
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Initialize two-microphone impedance tube methods
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Args:
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mnormal: Measurement in normal configuration
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mswitched: Measurement in normal configuration
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s: Microphone distance
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fl: Lower evaluation frequency
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fu: Lower evaluation frequency
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kwargs: tuple with extra arguments, of which:
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N: Period length of periodic excitation *obligatory*
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chan0: Measurement channel index of mic 0
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chan1: Measurement channel index of mic 1
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"""
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self.mnormal = mnormal
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self.mswitched = mswitched
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self.mat = mat
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self.s = s
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self.d1 = d1
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self.d2 = d2
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self.fl = fl
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if fl is None:
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ksmin = 0.1*pi
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kmin = ksmin/s
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self.fl = kmin*mat.c0/2/pi
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self.fu = fu
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if fu is None:
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ksmax = 0.8*pi
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kmax = ksmax/s
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self.fu = kmax*mat.c0/2/pi
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self.thermoviscous = thermoviscous
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self.D_imptube = D_imptube
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self.periodic_method = periodic_method
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self.channels = [kwargs.pop('chan0', 0), kwargs.pop('chan1', 1)]
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# Compute calibration correction
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if periodic_method:
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self.N = kwargs.pop('N')
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freq, C1 = mnormal.periodicCPS(self.N, channels=self.channels)
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freq, C2 = mswitched.periodicCPS(self.N, channels=self.channels)
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else:
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self.nfft = kwargs.pop('nfft', 16000)
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freq, C1 = mnormal.CPS(nfft=self.nfft, channels=self.channels)
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freq, C2 = mswitched.CPS(nfft=self.nfft, channels=self.channels)
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# Store this, as it is often used for just a single sample.
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self.C1 = C1
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self.freq = freq
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self.il = np.where(self.freq<= self.fl)[0][-1]
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self.ul = np.where(self.freq > self.fu)[0][0]
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# Calibration correction factor
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# self.K = 0*self.freq + 1.0
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K = sqrt(C2[:,0,1]*C1[:,0,0]/(C2[:,1,1]*C1[:,1,0]))
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# self.K = UnivariateSpline(self.freq, K.real)(self.freq) +\
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# 1j*UnivariateSpline(self.freq, K.imag)(self.freq)
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self.K = K
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def cut_to_limits(self, ar):
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return ar[self.il:self.ul]
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def getFreq(self):
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"""
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Array of frequencies, cut to limits of validity
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"""
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return self.cut_to_limits(self.freq)
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@lru_cache
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def G_AB(self, meas):
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if meas is self.mnormal:
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C = self.C1
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freq = self.freq
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else:
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if self.periodic_method:
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freq, C = meas.periodicCPS(self.N, self.channels)
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else:
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freq, C = meas.CPS(nfft=self.nfft, channels=self.channels)
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# Microphone transfer function
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G_AB = self.K*C[:,1,0]/C[:,0,0]
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return self.getFreq(), self.cut_to_limits(G_AB)
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def k(self, freq):
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"""
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Wave number, or thermoviscous wave number
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"""
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if self.thermoviscous:
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D = self.D_imptube
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S = pi/4*D**2
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d = PrsDuct(0, S=S, rh=D/4, cs='circ')
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d.mat = self.mat
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omg = 2*pi*freq
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G, Z = d.GammaZc(omg)
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return G
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else:
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return 2*pi*freq/self.mat.c0
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def R(self, meas):
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freq, G_AB = self.G_AB(meas)
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s = self.s
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k = self.k(freq)
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d1 = self.d1
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RpA = (G_AB - exp(-1j*k*s))/(exp(1j*k*s)-G_AB)
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R = RpA*exp(2*1j*k*(s+d1))
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return freq, R
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def alpha(self, meas):
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"""
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Acoustic absorption coefficient
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"""
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freq, R = self.R(meas)
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return freq, 1 - np.abs(R)**2
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def z(self, meas):
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"""
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Acoustic impedance at the position of the sample, in front of the sample
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"""
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freq, R = self.R(meas)
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return freq, self.mat.z0*(1+R)/(1-R)
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def zs(self, meas):
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"""
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Sample impedance jump, assuming a cavity behind the sample with
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thickness d2
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"""
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freq, R = self.R(meas)
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z0 = self.mat.z0
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k = 2*pi*freq/self.mat.c0
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d2 = self.d2
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zs = 2*z0*(1-R*exp(2*1j*k*d2))/((R-1)*(exp(2*d2*k*1j)-1))
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return freq, zs
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