# BeamformerBase¶

class acoular.fbeamform.BeamformerBase

Bases: traits.has_traits.HasPrivateTraits

Beamforming using the basic delay-and-sum algorithm in the frequency domain.

steer = Property(desc="steering vector object")

SteeringVector or derived object. Defaults to SteeringVector object.

freq_data = Trait(PowerSpectra, …

PowerSpectra object that provides the cross spectral matrix and eigenvalues

r_diag = Bool(True, …

Boolean flag, if ‘True’ (default), the main diagonal is removed before beamforming.

r_diag_norm = Float(0.0, …

If r_diag==True: if r_diag_norm==0.0, the standard normalization = num_mics/(num_mics-1) is used. If r_diag_norm !=0.0, the user input is used instead. If r_diag==False, the normalization is 1.0 either way.

precision = Trait('float64', 'float32', …

Floating point precision of property result. Corresponding to numpy dtypes. Default = 64 Bit.

cached = Bool(True, …

Boolean flag, if ‘True’ (default), the result is cached in h5 files.

result = Property( …

The beamforming result as squared sound pressure values at all grid point locations (readonly). Returns a (number of frequencies, number of gridpoints) array of floats.

sig_loss_norm()

If the diagonal of the CSM is removed one has to handle the loss of signal energy –> Done via a normalization factor.

calc(ac, fr)

Calculates the delay-and-sum beamforming result for the frequencies defined by freq_data

This is an internal helper function that is automatically called when accessing the beamformer’s result or calling its synthetic() method.

Parameters
acarray of floats

This array of dimension ([number of frequencies]x[number of gridpoints]) is used as call-by-reference parameter and contains the calculated value after calling this method.

frarray of booleans

The entries of this [number of frequencies]-sized array are either ‘True’ (if the result for this frequency has already been calculated) or ‘False’ (for the frequencies where the result has yet to be calculated). After the calculation at a certain frequency the value will be set to ‘True’

Returns
This method only returns values through the ac and fr parameters
synthetic(f, num=0)

Evaluates the beamforming result for an arbitrary frequency band.

Parameters
f: float

Band center frequency.

numinteger

Controls the width of the frequency bands considered; defaults to 0 (single frequency line).

num

frequency band width

0

single frequency line

1

octave band

3

third-octave band

n

1/n-octave band

Returns
array of floats

The synthesized frequency band values of the beamforming result at each grid point . Note that the frequency resolution and therefore the bandwidth represented by a single frequency line depends on the sampling frequency and used FFT block size.

integrate(sector)

Integrates result map over a given sector.

Parameters
sector: array of floats

Tuple with arguments for the ‘indices’ method of a Grid-derived class (e.g. RectGrid.indices or RectGrid3D.indices). Possible sectors would be array([xmin, ymin, xmax, ymax]) or array([x, y, radius]).

Returns
array of floats

The spectrum (all calculated frequency bands) for the integrated sector.