Octave¶
Module for working with octaves.
The following is an example on how to use acoustics.octave.Octave.
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acoustics.octave.exact_center_frequency(frequency=None, fraction=1, n=None, ref=1000.0)[source]¶ Exact center frequency.
Parameters: - frequency – Frequency within the band.
- fraction – Band designator.
- n – Index of band.
- ref – Reference frequency.
Returns: Exact center frequency for the given frequency or band index.
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acoustics.octave.nominal_center_frequency(frequency=None, fraction=1, n=None)[source]¶ Nominal center frequency.
Parameters: - frequency – Frequency within the band.
- fraction – Band designator.
- n – Index of band.
Returns: The nominal center frequency for the given frequency or band index.
Note
Contrary to the other functions this function silently assumes 1000 Hz reference frequency.
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acoustics.octave.lower_frequency(frequency=None, fraction=1, n=None, ref=1000.0)[source]¶ Lower band-edge frequency.
Parameters: - frequency – Frequency within the band.
- fraction – Band designator.
- n – Index of band.
- ref – Reference frequency.
Returns: Lower band-edge frequency for the given frequency or band index.
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acoustics.octave.upper_frequency(frequency=None, fraction=1, n=None, ref=1000.0)[source]¶ Upper band-edge frequency.
Parameters: - frequency – Frequency within the band.
- fraction – Band designator.
- n – Index of band.
- ref – Reference frequency.
Returns: Upper band-edge frequency for the given frequency or band index.
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acoustics.octave.index_of_frequency(frequency, fraction=1, ref=1000.0, G=1.9952623149688795)[source]¶ Determine the band index x from a given frequency.
Parameters: - frequency – Frequencies \(f\).
- fraction – Bandwidth designator \(b\).
- ref – Reference frequency.
- G – Octave frequency ratio \(G\).
The index of the center frequency is given by
\[x = round{b \frac{\log{f/f_{ref} }}{\log{G} }}\]Note
This equation is not part of the standard. However, it follows from
exact_center_frequency().
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class
acoustics.octave.Octave(fraction=1, interval=None, fmin=None, fmax=None, unique=False, reference=1000.0)[source]¶ Class to calculate octave center frequencies.
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__init__(fraction=1, interval=None, fmin=None, fmax=None, unique=False, reference=1000.0)[source]¶ Initialize self. See help(type(self)) for accurate signature.
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bandwidth¶ Bandwidth of bands.
\[B = f_u - f_l\]
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center¶ Return center frequencies \(f_c\).
\[f_c = f_{ref} \cdot 2^{n/N} \cdot 10^{\frac{3}{10N}}\]
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fmax¶ Maximum frequency of an interval.
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fmin¶ Minimum frequency of an interval.
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fraction= None¶ Fraction of octave.
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interval¶ Interval.
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lower¶ Lower frequency limits of bands.
\[f_l = f_c \cdot 2^{\frac{-1}{2N}}\]See also
lower_frequency().
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n¶ Return band
nfor a given frequency.
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reference= None¶ Reference center frequency \(f_{c,0}\).
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unique= None¶ Whether or not to calculate the requested values for every value of
interval.
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upper¶ Upper frequency limits of bands.
\[f_u = f_c \cdot 2^{\frac{+1}{2N}}\]See also
upper_frequency().
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acoustics.octave.frequency_of_band(x, fraction=1, ref=1000.0, G=1.9952623149688795)¶ Center frequencies \(f_m\) for band indices \(x\). See equation 2 and 3.
Parameters: - x – Band index \(x\).
- ref – Reference center frequency \(f_r\).
- fraction – Bandwidth designator :math`b`. For example, for 1/3-octave filter b=3.
- G – Octave frequency ratio \(G\).
The center frequencies are given by
\[f_m = f_r G^{x/b}\]In case the bandwidth designator \(b\) is an even number, the center frequencies are given by
\[f_m = f_r G^{(2x+1)/2b}\]See equation 2 and 3 of the standard.
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acoustics.octave.band_of_frequency(frequency, fraction=1, ref=1000.0, G=1.9952623149688795)¶ Determine the band index x from a given frequency.
Parameters: - frequency – Frequencies \(f\).
- fraction – Bandwidth designator \(b\).
- ref – Reference frequency.
- G – Octave frequency ratio \(G\).
The index of the center frequency is given by
\[x = round{b \frac{\log{f/f_{ref} }}{\log{G} }}\]Note
This equation is not part of the standard. However, it follows from
exact_center_frequency().