84 lines
2.3 KiB
Python
84 lines
2.3 KiB
Python
# -*- coding: utf-8 -*-
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"""!
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Author: J.A. de Jong - ASCEE
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Description:
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Reverberation time estimation tool using least squares
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"""
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from .lasp_common import getTime
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import numpy as np
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class ReverbTime:
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"""
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Tool to estimate the reverberation time
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"""
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def __init__(self, fs, level, channel=0):
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"""
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Initialize Reverberation time computer.
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Args:
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fs: Sampling frequency [Hz]
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level: (Optionally weighted) level values as a function of time, in
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dB.
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channel: Channel index to compute from
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"""
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assert level.ndim == 2, 'Invalid number of dimensions in level'
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self._level = level[:, channel][:, np.newaxis]
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# Number of time samples
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self._channel = channel
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self._N = self._level.shape[0]
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self._t = getTime(fs, self._N, 0)
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print(f't: {self._t}')
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def compute(self, istart, istop):
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"""
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Compute the reverberation time using a least-squares solver
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Args:
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istart: Start time index reverberation interval
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istop: Stop time index of reverberation interval
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Returns:
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dictionary with result values, contains:
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- istart: start index of reberberation interval
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- istop: stop index of reverb. interval
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- T60: Reverberation time
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- const: Constant value
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- derivative: rate of change of the level in dB/s.
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"""
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points = self._level[istart:istop]
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x = self._t[istart:istop][:, np.newaxis]
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# Solve the least-squares problem, by creating a matrix of
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A = np.hstack([x, np.ones(x.shape)])
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# print(A.shape)
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# print(points.shape)
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# derivative is dB/s of increase/decrease
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sol, residuals, rank, s = np.linalg.lstsq(A, points)
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# print(f'sol: {sol}')
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# Derivative of the decay in dB/s
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derivative = sol[0][0]
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# Start level in dB
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const = sol[1][0]
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# Time to reach a decay of 60 dB (reverb. time)
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T60 = -60./derivative
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res = {'istart': istart,
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'istop': istop,
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'const': const,
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'derivative': derivative,
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'T60': T60}
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# print(res)
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return res
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