Receiver 2D and Receiver 3D
Use a Receiver 2D () or Receiver 3D dataset (), selected from the More 2D Datasets submenu and the More 3D Datasets submenu, respectively, to collect the data necessary to visualize the impulse response for a Ray Acoustics simulation (of room acoustics, for example), using an Impulse Response plot node in a 1D plot group. The Impulse Response node uses the data from a Receiver dataset as input.
See Common Results Node Settings for links to information about the Data section.
Receiver
The receiver is specified as a sphere with a radius, located at a center position (the microphone needs to have a certain finite size such that there is a reasonable probability of rays interacting with it).
Under Center, specify the x, y, and (3D only) z coordinates for the center of the receiver.
Under Radius, specify the radius of the receiver. From the Radius input list, choose Variable size (large room volume) to determine the radius using an expression (see below), or choose Fixed size to enter a value for the radius in the Radius field (SI unit: m).
The following expression determines the radius R of the receiver in room acoustics applications:
where you enter the values for the Number of rays, N; Room volume, V (SI unit: m2); and Source-receiver distance, dSR (SI unit: m), to determine the radius. This computed receiver size is optimized for modeling of large rooms. However, it will return a different value for each source-receiver pair if there are multiple sources and receivers present in the simulation, and it will not necessarily correspond to the dimensions of a listener.
Directivity
From the Directivity type list, choose Omnidirectional (the default), User defined (dB), or User defined (linear) too enter a directivity expression in the Expression field either as a gain in dB or a linear gain. The linear gain option also allows the input to be negative, which corresponds to a shift in phase. Click the Replace Expression () button to choose an expression from available predefined expressions.
Extra Time Steps
An impulse response plot requires a precise evaluation of arrival times. You can control the added extra time steps from the Maximum number of extra time steps rendered list:
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Choose All (the default) to render all extra time steps. This setting is the preferred and most efficient.
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Choose Specified number of times to enter a maximum number of steps in the Maximum number of extra time steps field (default: 100).
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Choose Proportional to the number of solution times to enter a factor in the Proportionality factor field. The proportionality factor is a positive integer.
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Choose None to not add any extra time steps.
Advanced
From the Interpolation between time steps list, you can choose to use a Linear interpolation (the default) or a Cubic interpolation, which can be more exact but requires a larger computational effort.
Under Normal variables and Other variables, if desired, you can change the default names of the created variables for the normal directions (nx, ny, and, in 3D, nz) and for the Distance traveled by a ray inside the receiver, the Volume of the receiver, the Directivity, and the First ray arrival time.
Receiver datasets require the Acoustics Module.