MovingPointSourceDipole#

class acoular.sources.MovingPointSourceDipole

Bases: PointSourceDipole, MovingPointSource

Define a moving point source with dipole characteristics.

This class extends the functionalities of PointSourceDipole and MovingPointSource to simulate a dipole source that moves along a defined trajectory. It incorporates both rotational and translational dynamics for the dipole lobes, allowing simulation of complex directional sound sources.

Key Features:

  • Combines dipole characteristics with source motion.

  • Supports rotation of the dipole directivity via the rvec attribute.

  • Calculates emission times using Newton-Raphson iteration.

See also

PointSourceDipole

For stationary dipole sources.

MovingPointSource

For moving point sources without dipole characteristics.

digest

A unique identifier for the current state of the source, based on its properties. (read-only)

rvec

A reference vector, perpendicular to the x and y-axis of moving source, defining the axis of rotation for the dipole directivity. If set to (0, 0, 0), the dipole is only translated along the trajectory without rotation. Default is (0, 0, 0).

get_emission_time(t, direction)

Calculate the emission time and related properties for a moving source.

Parameters:
tnumpy.ndarray

The current receiving time at the microphones.

directionfloat or numpy.ndarray

Direction vector for the source’s dipole directivity.

Returns:
tuple

A tuple containing:

Warning

Ensure that the maximum iteration count (100) is sufficient for convergence in all scenarios, especially for high Mach numbers or long trajectories.

Notes

The emission times are computed iteratively using the Newton-Raphson method. The iteration terminates when the time discrepancy (eps) is below a threshold (epslim) or after 100 iterations.

result(num=128)

Generate the output signal at microphones in blocks.

Parameters:
numint, optional

Number of samples per block to yield. Default is 128.

Yields:
numpy.ndarray

A 2D array of shape (num, num_channels) containing the signal detected at the microphones. The last block may have fewer samples if num_samples is not a multiple of num.

Notes

Radial Mach number adjustments are applied if conv_amp is enabled.

get_moving_direction(direction, time=0)

Calculate the moving direction of the source along its trajectory.

This method computes the updated direction vector for the moving source, considering both translation along the trajectory and rotation defined by the reference vector. If the reference vector is (0, 0, 0), only translation is applied. Otherwise, the method incorporates rotation into the calculation.

Parameters:
directionnumpy.ndarray

The initial orientation of the source, specified as a three-dimensional array.

timefloat, optional

The time at which the trajectory position and velocity are evaluated. Defaults to 0.

Returns:
numpy.ndarray

The updated direction vector of the moving source after translation and, if applicable, rotation. The output is a three-dimensional array.

Notes

  • The method computes the translation direction vector based on the trajectory’s velocity at the specified time.

  • If the reference vector is non-zero, the method constructs a rotation matrix to compute the new source direction based on the trajectory’s motion and the reference vector.

  • The rotation matrix ensures that the new orientation adheres to the right-hand rule and remains orthogonal.

direction

Vector defining the orientation of the dipole lobes and the distance between the inversely phased monopoles. The magnitude of the vector determines the monopoles’ separation:

  • distance = [lowest wavelength in spectrum] * [magnitude] * 1e-5

Use vectors with magnitudes on the order of 1.0 or smaller for best results. Default is (0.0, 0.0, 1.0) (z-axis orientation).

Note: Use vectors with order of magnitude around 1.0 or less for good results.

prepadding

Behavior of the signal for negative time indices. Currently only supports 'loop'. Default is 'loop'.

conv_amp

Determines whether convective amplification is considered. When True, the amplitude of the signal is adjusted based on the relative motion between the source and microphones. Default is False.

trajectory

Instance of the Trajectory class specifying the source’s motion. The trajectory defines the source’s position and velocity at any given time.

signal

Instance of the SignalGenerator class defining the emitted signal.

loc

Coordinates (x, y, z) of the source. Default is np.array([[0.0], [0.0], [1.0]]).

num_channels

Number of output channels, automatically set based on the microphone geometry.

mics

MicGeom object defining the positions of the microphones.

env

An Environment or derived object providing sound propagation details, such as speed of sound in the medium. Default is Environment.

start_t

Start time of the signal in seconds. Default is 0.0.

start

Start time of data acquisition at the microphones in seconds. Default is 0.0.

up

Internal upsampling factor for finer signal resolution. Default is 16.

num_samples

Total number of samples in the emitted signal, derived from the signal generator.

sample_freq

Sampling frequency of the signal, derived from the signal generator.