`FiltFiltOctave`#

class acoular.tprocess.FiltFiltOctave

Bases: FiltOctave

Octave or third-octave bandpass filter with zero-phase distortion.

This filter applies an IIR bandpass filter in both forward and reverse directions, effectively eliminating phase distortion. It provides zero-phase filtering but requires significantly more memory compared to causal filtering.

See also

Filter: The base class implementing a general IIR filter.
FiltOctave: The standard octave or third-octave filter with causal filtering.

Notes

Due to the double-pass filtering, additional bandwidth correction is applied to maintain accurate frequency response.
This approach requires storing the entire signal in memory before processing, making it unsuitable for real-time applications with large datasets.

order: The half-order of the IIR filter, applied twice (once forward and once backward). This results in a final filter order twice as large as the specified value. Default is 2.

digest: A unique identifier for the filter, based on its properties. (read-only)

result(num)

Apply the filter to the input signal and yields filtered data block-wise.

The input signal is first stored in memory, then filtered in both forward and reverse directions to achieve zero-phase distortion. The processed signal is yielded in blocks.

Parameters:

numint: Number of samples per block.

Yields:

numpy.ndarray: An array containing the filtered signal for the current block. Each block has shape (num, num_channels), where num_channels is inherited from the source. The last block may contain fewer samples if the total number of samples is not a multiple of num.

Notes

This method requires the entire signal to be stored in memory, making it unsuitable for streaming or real-time applications.
Filtering is performed separately for each channel to optimize memory usage.

band: The center frequency of the octave or third-octave band. Default is 1000.

fraction

Defines whether the filter is an octave-band or third-octave-band filter.

'Octave': Full octave band filter.
'Third octave': Third-octave band filter.

Default is 'Octave'.

sos: Second-order sections representation of the filter coefficients. This property depends on band, fraction, order, and the source’s digest.

source: The input data source. It must be an instance of a SamplesGenerator-derived class.

sample_freq: Sampling frequency of output signal, as given by source.

num_channels: Number of channels in output, as given by source.

num_samples: Number of samples in output, as given by source.

FiltFiltOctave#

`FiltFiltOctave`#