Low-Order Filter Approximation of Diffraction for Virtual Acoustics

Kirsch, Christoph; Ewert, Stephan D.

doi:10.1109/waspaa52581.2021.9632674

Cited by 7 publications

(8 citation statements)

References 19 publications

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“…A prominent feature of UDFA is the validity in all three zones including the view and reflection zone, whereas some earlier approaches [16], [48] only considered the shadow zone. Additionally, when only considering the shadow zone, the current (most efficient) single-term solution for infinite wedges can also be applied for finite wedges (including a DC gain) resulting in a close approximation for sufficiently large bending angles, while also converging to a flat response with unity gain at the shadow boundary.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…To ensure a smooth transition to the GA direct sound component, unity gain at the shadow boundary can be achieved by using a single filter (see, e.g. [48] for a heuristically derived expression). The exact cutoff frequency for a single low-pass filter with unity gain at DC and asymptotically matching the two-term filter representation (3,4), can be derived as…”

Section: B Two-and Single-term Approximationmentioning

confidence: 99%

“…Here, the simplest expression [50] can be applied in UDFA similar to [48], using the bending angle 𝜃 b :…”

Section: B Two-and Single-term Approximationmentioning

confidence: 99%

“…In this case, it is desired that the effect of diffraction disappears at the shadow boundary and asymptotes against unity gain [16], [36]. A computationally efficient parametric infinite impulse response (IIR) filter approximation of diffraction effects for the shadow zone based on the infinite knife edge was proposed in [48]. In general, such low-order IIR filters (also see, e.g., [2] for a warped IIR design) offer high computational efficiency and the ability to conveniently interpolate filter coefficients in timevariant geometrical conditions.…”

Section: Introductionmentioning

confidence: 99%

“…A parametric design for recursive (IIR) filters with scalable precision is proposed, enabling straight forward interpolation of the filter coefficients in time-variant geometrical conditions in VAEs. The remainder of this paper is structured as follows: Section II outlines the underlying filter representation [50] for infinite wedges and derives an exact solution for the heuristic filter approximation in [48]. Section III derives the filter approximation for finite wedges.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

A Universal Filter Approximation of Edge Diffraction for Geometrical Acoustics

Kirsch

Ewert

2023

IEEE/ACM Trans. Audio Speech Lang. Process.

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Sound propagation in urban and indoor environments often involves diffraction at corners, finite objects and openings, resulting in perceptually relevant frequencydependent attenuation. Geometrical acoustics (GA) have become a de-facto standard for prediction and simulation of sound propagation and real-time virtual acoustics, including effects of edge diffraction. However, methods to account for edge diffraction often assume infinite edges, such as the uniform theory of diffraction or are computationally involved, such as the Biot-Tolstoy-Medwin-Svensson (BTMS) method. Particularly for interactive auralization, an efficient approximation of edge diffraction is desirable. Here, an extension of GA to account for diffraction with simple-to-derive parameters and a time-domain recursive filter implementation is suggested. This universal diffraction filter approximation (UDFA) describes diffraction from infinite and finite wedges using a combination of first-order and (fractional) half-order low-pass filters to account for the frequency-dependent attenuation of the diffracted incident and reflected sound field. The physically-based UDFA exactly matches asymptotic solutions for infinite wedges and provides approximations for finite wedges. It is demonstrated that firstorder diffraction from flat finite objects like a plate or an aperture can be described by combining the filters for each edge. To account for effects of higher-order diffraction, an additional heuristic filter extension is suggested.

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Section: Summary and Discussionmentioning

confidence: 99%

Section: B Two-and Single-term Approximationmentioning

confidence: 99%

“…Here, the simplest expression [50] can be applied in UDFA similar to [48], using the bending angle 𝜃 b :…”

Section: B Two-and Single-term Approximationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Universal Filter Approximation of Edge Diffraction for Geometrical Acoustics

Kirsch

Ewert

2023

IEEE/ACM Trans. Audio Speech Lang. Process.

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Filter-based first- and higher-order diffraction modeling for geometrical acoustics

Kirsch,

Ewert

2024

Acta Acust.

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Geometrical acoustics (GA) offers a high computational efficiency, as required for real-time renderings of complex acoustic environments with applications in, e.g., hearing research, architectural planning, and entertainment. However, the assumed ray-like sound propagation does not account for perceptually relevant effects of diffraction. In indoor environments, diffraction at finite objects and apertures such as tables, music stands, and doors is of interest for computationally efficient rendering. Outdoors, buildings and barriers are relevant. Here, we extend the recent physically-based universal diffraction filter approximation (UDFA) for GA to approximate spectral effects of higher-order diffraction and apply it to a flat finite object and a double edge. At low frequencies, such effects predominantly occur when sound is diffracted repeatedly at the edges of a finite object, and at high frequencies when sound is propagating around subsequent edges of, e.g., buildings or sound barriers. In contrast to existing methods, the suggested filter approaches and topology offer spatially smooth infinite impulse response implementation for modelling higher-order diffraction at flat objects for arbitrary geometrical arrangements. For double diffraction at a three-sided barrier, errors are considerably decreased in comparison to a state-of-the-art sequential approach. Both suggested methods are computationally highly efficient and scalable depending on the desired accuracy.

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A filter representation of diffraction at infinite and finite wedges

Ewert

2022

JASA Express Letters

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Diffraction of sound occurs at sound barriers, building and room corners in urban and indoor environments. Here, a unified parametric filter representation of the singly diffracted field at arbitrary wedges is suggested, connecting existing asymptotic and exact solutions in the framework of geometrical acoustics. Depending on the underlying asymptotic (high-frequency) solution, a combination of up to four half-order lowpass filters represents the diffracted field. Compact transfer function and impulse response expressions are proposed, providing errors below ±0.1 dB. To approximate the exact solution, a further asymptotic lowpass filter valid at low frequencies is suggested and combined with the high-frequency filter.

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Low-Order Filter Approximation of Diffraction for Virtual Acoustics

Cited by 7 publications

References 19 publications

A Universal Filter Approximation of Edge Diffraction for Geometrical Acoustics

A Universal Filter Approximation of Edge Diffraction for Geometrical Acoustics

Filter-based first- and higher-order diffraction modeling for geometrical acoustics

A filter representation of diffraction at infinite and finite wedges

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