102 lines
2.4 KiB
Python
102 lines
2.4 KiB
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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"""
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Sound level meter implementation
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@author: J.A. de Jong - ASCEE
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"""
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from .wrappers import Slm as pyxSlm
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import numpy as np
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from .lasp_common import (TimeWeighting, P_REF)
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__all__ = ['SLM', 'Dummy']
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class Dummy:
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"""
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Emulate filtering, but does not filter anything at all.
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"""
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def filter_(self, data):
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return data[:, np.newaxis]
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class SLM:
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"""
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Multi-channel Sound Level Meter. Input data: time data with a certain
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sampling frequency. Output: time-weighted (fast/slow) sound pressure
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levels in dB(A/C/Z). Possibly in octave bands.
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"""
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def __init__(self, fs, tw=TimeWeighting.default, ):
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"""
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Initialize a sound level meter object.
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Number of channels comes from the weighcal object.
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Args:
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fs: Sampling frequency [Hz]
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tw: Time Weighting to apply
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"""
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if tw[0] is not TimeWeighting.none[0]:
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# Initialize the single-pole low-pass filter for given time-
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# weighting value.
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self._lp = SPLowpass(fs, tw[0])
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else:
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self._lp = Dummy()
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self._Lmax = 0.
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# Storage for computing the equivalent level
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self._sq = 0. # Square of the level data, storage
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self._N = 0
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self._Leq = 0.
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@property
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def Leq(self):
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"""
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Returns the equivalent level of the recorded signal so far
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"""
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return self._Leq
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@property
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def Lmax(self):
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"""
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Returns the currently maximum recorded level
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"""
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return self._Lmax
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def addData(self, data):
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"""
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Add new fresh timedata to the Sound Level Meter
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Args:
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data:
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returns:
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level values as a function of time
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"""
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assert data.ndim == 2
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assert data.shape[1] == 1
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P_REFsq = P_REF**2
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# Squared
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sq = data**2
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# Update equivalent level
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N1 = sq.shape[0]
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self._sq = (np.sum(sq) + self._sq*self._N)/(N1+self._N)
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self._N += N1
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self._Leq = 10*np.log10(self._sq/P_REFsq)
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# Time-weight the signal
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tw = self._lp.filter_(sq)
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Level = 10*np.log10(tw/P_REFsq)
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# Update maximum level
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curmax = np.max(Level)
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if curmax > self._Lmax:
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self._Lmax = curmax
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return Level
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