`MovingLineSource`#

class acoular.sources.MovingLineSource

Bases: LineSource, MovingPointSource

A moving line source with an arbitrary signal.

The MovingLineSource class models a line source composed of multiple monopoles that move along a trajectory. It supports coherent and incoherent sources and considers Doppler effects due to motion.

Key Features:

Specify the trajectory and rotation of the line source.
Compute emission times considering motion and source direction.
Generate block-wise microphone output with moving source effects.

See also

LineSource: For line sources consisting of coherent or incoherent monopoles.
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 line source directivity. If set to (0, 0, 0), the line source is only translated along the trajectory without rotation. Default is (0, 0, 0).

get_emission_time(t, direction)

Calculate the emission time for a moving line source based on its trajectory.

This method computes the time at which sound waves are emitted from the line source at a specific point along its trajectory. It also determines the distances from the source to each microphone and calculates the radial Mach number, which accounts for the Doppler effect due to the motion of the source.

Parameters:

tfloat: The current receiving time at the microphones, specified in seconds.
directionnumpy.ndarray: The current direction vector of the line source, specified as a 3-element array representing the orientation of the line.

Returns:

tenumpy.ndarray: The computed emission times for each microphone, specified as an array of floats.
rmnumpy.ndarray: The distances from the line source to each microphone, represented as an array of absolute distances.
Mrnumpy.ndarray: The radial Mach number, which accounts for the Doppler effect, calculated for each microphone.
xsnumpy.ndarray: The position of the line source at the computed emission time, returned as a 3-element array.

Notes

This method performs Newton-Raphson iteration to find the emission time where the sound wave from the source reaches the microphones.
The distance between the line source and microphones is computed using Euclidean geometry.
The radial Mach number (Mr) is calculated using the velocity of the source and the speed of sound in the medium (c).
The method iterates until the difference between the computed emission time and the current time is sufficiently small (within a defined threshold).

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.

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 to define the orientation of the line source. Default is (0.0, 0.0, 1.0).

length: Vector to define the length of the line source in meters. Default is 1.0.

num_sources: Number of monopole sources in the line source. Default is 1.

source_strength: Strength coefficients for each monopole source.

coherence: Coherence mode for the monopoles ('coherent' or 'incoherent').

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.

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

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.

MovingLineSource#

`MovingLineSource`#