Diffraction Enhanced Image Source Method - Arbitrary Room Geometry (DEISM-ARG)

The code in this folder is able to solve the following problem:

A source and a receiver transducer with arbitrary directivity are mounted on one/two speakers; The local scattering and diffraction effects around the transducers result in complex directivity patterns. The directivity patterns can be obtained by analytical expressions, numerical simulations or measurements.

In DEISM-ARG, we can model the room transfer function between transducers mounted on one/two speakers using the image source method while incorporating the local diffraction effects around the transducers. The local diffraction effects are captured using spherical-harmonic directivity coefficients obtained on a sphere around the transducers. In addition to DEISM in shoebox rooms, DEISM-ARG can model more complex room shapes. However, for version 2.0, we now only supports convex shapes. In short, DEISM-ARG has the following features:

1. Arbitrary directivities of the source and receiver
2. Angle-dependent reflection coefficients, frequency- and wall-dependent impedance definition.
3. Convex room shapes

📚 Documentation

📖 Read the full documentation on Read the Docs

Installation

DEISM supports Python 3.10, 3.11, and 3.12 on Windows, Linux, and Apple Silicon macOS. Intel macOS is not supported, because the numba dependency no longer builds there. The current documentation is organized around the class-based workflow implemented by deism.core_deism.DEISM.

Useful entry points:

• Quickstart
• Workflows
• Parameter dependencies
• Configuration

Local HTML playground

After installing this version of DEISM, run deism-playground from any directory. It serves the packaged UI on localhost, starts one persistent Python simulation process, and opens your browser. No Node.js or manual HTML build is needed. Ctrl+C stops both processes. Use deism-playground --no-browser --port 8765 to choose a port and open the page yourself.

The sampled-directivity MAT datasets (186 MB) are not included in the wheels. On the first run the launcher downloads them from the GitHub release into ~/.cache/deism/sampled_directivity; a checkout in the working directory (examples/data/sampled_directivity, after git lfs pull) or the --data-dir option is used instead when present, --no-download skips the download, and --clear-cache removes the copy. Monopole transducers work without them.

The live preview uses JavaScript with reduced settings; Run Python DEISM uses the installed Python workflow and the original MAT datasets. See playground usage and validation for supported settings, performance measurements, and offline-demo limitations.

Check Python version

On macOS or Linux:

python3 --version

On Windows PowerShell:

python --version

If you do not have a supported Python version, install one from python.org.

Installation method 1: Python virtual environment

End users

On macOS or Linux:

python3 -m venv ~/.venv/deism
source ~/.venv/deism/bin/activate
python -m pip install --upgrade pip
python -m pip install deism

On Windows PowerShell:

python -m venv C:\Users\<YourUsername>\venvs\deism
C:\Users\<YourUsername>\venvs\deism\Scripts\Activate.ps1
python -m pip install --upgrade pip
python -m pip install deism

If PowerShell blocks activation, run:

Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

Developers

On macOS or Linux:

git clone https://github.com/audiolabs/DEISM.git
cd DEISM
python3 -m venv ~/.venv/deism_dev
source ~/.venv/deism_dev/bin/activate
python -m pip install --upgrade pip
python -m pip install -r requirements.txt
python -m pip install -e .

On Windows PowerShell:

git clone https://github.com/audiolabs/DEISM.git
cd DEISM
python -m venv C:\Users\<YourUsername>\venvs\deism_dev
C:\Users\<YourUsername>\venvs\deism_dev\Scripts\Activate.ps1
python -m pip install --upgrade pip
python -m pip install -r requirements.txt
python -m pip install -e .

DEISM reads pre-generated convex-room .msh files through meshio. Geometry scripts such as .geo must be meshed before they are passed to DEISM. The room must be convex, and every wall must carry exactly one named Physical Surface whose name matches its material key; the reader rejects non-convex rooms, untagged or unnamed walls, and surfaces that cover only part of a wall.

Installation method 2: Conda environment

End users

conda create -n deism python=3.12
conda activate deism
python -m pip install --upgrade pip
python -m pip install deism

Developers

git clone https://github.com/audiolabs/DEISM.git
cd DEISM
conda env create -f deism_env.yml
conda activate DEISM
python -m pip install -e .

Build tools for source installs

Published wheels include DEISM's two C++ extensions. Building from a source checkout or source distribution requires a working C++ compiler.

macOS:

xcode-select --install

Ubuntu or Debian:

sudo apt-get update
sudo apt-get install build-essential g++ python3-dev

RHEL, CentOS, or Fedora:

sudo yum install gcc-c++ python3-devel

Windows:

• Install Visual Studio Build Tools with the C++ workload.

Verify the installation

Basic import check:

python -c "import deism; print('DEISM import OK')"

Native-extension check:

python -c "from deism import libroom_deism; from deism.count_reflections_wrapper import CPP_COUNTING_AVAILABLE; assert libroom_deism and CPP_COUNTING_AVAILABLE"

Quick help check:

python examples/deism_singleparam_example.py --help

Quick smoke run:

python examples/deism_singleparam_example.py

Additional notes

• Some plotting utilities use matplotlib with text.usetex = True, so a LaTeX installation may be needed for figure rendering. See the Matplotlib usetex documentation.
• Most example outputs are written below outputs/.

Running DEISM

The current public workflow is class-based:

from deism.core_deism import DEISM

deism = DEISM("RIR", "shoebox")
deism.update_room()
deism.update_wall_materials()
deism.update_freqs()
deism.update_directivities()
deism.update_source_receiver()
deism.run_DEISM()

Default configuration files

DEISM selects its default YAML configuration from the pair (mode, roomtype):

These files are also bundled with installed wheels and source distributions. Repository-local files retain precedence, while an installed package falls back to its bundled defaults when invoked from another working directory.

Workflow order

Shoebox workflow:

• update_room()
• update_wall_materials()
• update_freqs()
• update_directivities() and update_source_receiver() in either order
• update_fluctuations() (optional atmospheric path-length fluctuations; see the fluctuation paper)
• run_DEISM()

Convex workflow:

• update_room()
• update_wall_materials()
• update_freqs()
• update_source_receiver()
• update_directivities()
• update_fluctuations() (optional; must follow update_source_receiver())
• run_DEISM()

The convex order is stricter because ARG directivity setup depends on reflection-path state computed during update_source_receiver().

Recommended starting examples

Beginner examples:

• examples/deism_singleparam_example.py for the current shoebox path
• examples/deism_arg_singleparam_example.py for the current convex path

Advanced or research-oriented examples:

• examples/deisms_lc_mix_test.py
• examples/shoebox_images_cal_compare.py
• examples/deism_args_compare.py
• examples/deism_arg_pra_compare.py
• examples/deism_arg_IWAENC_fig5_fig6.py
• examples/deism_JASA_fig8.py
• examples/deism_JASA_fig9.py
• examples/deism_volatility_example.py (shoebox atmospheric fluctuations)
• examples/deism_arg_volatility_example.py (convex atmospheric fluctuations)

For more detail, use the docs pages linked above instead of relying only on the older example scripts.

Directivities

Modeling the directivities of the source and receiver in the room acoustics simulation is receiving increasing attention. The directivities of the source or receiver can include both the transducer directional properties and the local diffraction and scatterring effects caused by the enclosure where the transducers are mounted. Modern smart speakers are typical embodiments of such scenarios. Human heads are also a very common case.

Simple directivities

• Monopole

Arbitrary directivities

Some key information should be provided if you want to include your own directivity data:

1. Frequencies at which the directivities are simulated or measured. A 1D array.
2. The spherical sampling directions around the transducer: azimuth from $0$ ( $+x$ direction) to $2 \pi$, inclination angle from $0$ ($+z$ direction) to $\pi$. A 2D array with size (number of directions, 2).
3. The sampled pressure field at the specified directions and frequencies. A 2D array with size (number of frequencies, number of directions).
4. The radius of the sampling sphere. A 1D array or float number.

For more information about directivity definition used in DEISM and DEISM-ARG, please refer to the following publication:

Zeyu Xu, Adrian Herzog, Alexander Lodermeyer, Emanuël A. P. Habets, Albert G. Prinn; Acoustic reciprocity in the spherical harmonic domain: A formulation for directional sources and receivers. JASA Express Lett. 1 December 2022; 2 (12): 124801. https://doi.org/10.1121/10.0016542

Contributors

• M. Sc. Zeyu Xu
• Songjiang Tan
• M. Sc. Hasan Nazım Biçer
• Dr. Albert Prinn
• Prof. Dr. ir. Emanuël Habets
• Anjana Rajasekhar
• M. Sc. Jeremy Lawrence

Academic publications

If you use this package in your research, please cite our paper:

Zeyu Xu, Adrian Herzog, Alexander Lodermeyer, Emanuël A. P. Habets, Albert G. Prinn; Simulating room transfer functions between transducers mounted on audio devices using a modified image source method. J. Acoust. Soc. Am. 1 January 2024; 155 (1): 343–357. https://doi.org/10.1121/10.0023935

Z. Xu, E.A.P. Habets and A.G. Prinn; Simulating sound fields in rooms with arbitrary geometries using the diffraction-enhanced image source method, Proc. of International Workshop on Acoustic Signal Enhancement (IWAENC), 2024.

The optional atmospheric path-length fluctuations (drift, volatility, fluctuationSeed; update_fluctuations()) implement the model of:

Jeremy Lawrence, Zeyu Xu, Andreas Walther, Nils Peters, Emanuël A. P. Habets; Integrating atmospheric fluctuations into the image source method. JASA Express Lett. 1 July 2026; 6 (7): 072401. https://doi.org/10.1121/10.0044473

Configuration files

The current default configuration files are:

• examples/configSingleParam_RTF.yml for shoebox RTF
• examples/configSingleParam_RIR.yml for shoebox RIR
• examples/configSingleParam_ARG_RTF.yml for convex RTF
• examples/configSingleParam_ARG_RIR.yml for convex RIR

See docs/configuration.rst for the configuration groups and runtime parameter mappings.

Speed of the convex pipeline

The convex (DEISM-ARG) workflow has three costly stages: finding the image sources, refitting the source directivity for every image, and the solver. All three were accelerated (September 2026): images, coefficients and RTFs matched the previous implementation bit-for-bit in the tested configurations. The defaults select the fast paths; the switches below exist for validation and for bounding temporary memory.

• Image finding (deism/libroom_src/room.cpp): the image-source DFS tracks, for each candidate image, the region of its generating wall through which a path to it must pass, and skips the subtree when that region is empty (beam tracing with a conservative margin; every remaining candidate still runs the original visibility test). deism.room_convex.room_engine.beam_pruning = False restores the exhaustive search; dfs_nodes_visited and dfs_subtrees_pruned report the counts. beam_margin must be finite and nonnegative. Both pruning settings are preserved when the wrapper rebuilds its engine after parameter changes. Rebuild the extension after updating the sources.
• Source refit (cal_C_nm_s_arg, fast path): images are fitted in batches (one spherical-harmonic evaluation and one LAPACK solve per batch), each distinct reflection matrix is fitted once (directivityRefitReuseIdentical, default 1; exact byte equality, no rounding), and the coefficients are written straight into the complex64 tensor. directivityRefitBatchImages (default 256) and directivityRefitUniqueBudgetMiB (default 256) bound the temporaries. cal_C_nm_s_arg(..., out_dtype=np.complex64) requests the compact output directly; the default return type is unchanged.
• Wigner 3j tables (pre_calc_Wigner): exact-rational evaluation with a process cache; params["wignerMethod"] = "sympy" selects the original sympy loop.
• LC solver kernel: image-major coefficient batches (numbaArgLcBatchImages, default 512).

python benchmarks/bench_convex_directivity_images.py times every stage of a checkout; --root measures another checkout and --compare prints the before/after table. Measured on the IWAENC Fig. 5 room (MIX, SH 5/5, 491 frequencies, warmed, 4 cores) the stages changed as follows (seconds, old -> new):

Warm medians of three repetitions in one process; the old numbers come from the pre-optimization commit measured by the same script. Peak process RSS for the order-15 case fell from 4.9 GB to 2.1 GB. The full table and the isolated effect of each switch are produced by benchmarks/bench_convex_directivity_images.py.

Compact image storage

Image generation and reflection attenuation are decoupled by default in both room types ("compact" mode): the image-source engine emits frequency- independent path geometry, and the frequency-dependent attenuation is rebuilt from it by a parallel numba kernel. This makes image generation independent of the number of frequencies and avoids holding the full (n_images, n_frequencies) attenuation array.

Each room type has its own flag, because the two paths were implemented separately and rebuild attenuation at different points:

Set either flag to 0 for the legacy materialized path. Neither flag is read from the YAML configuration files or the command line — both are set programmatically, e.g. deism.params["convexCompactImages"] = 0.

Shoebox rooms

Compact shoebox storage is produced only by the numba image generator (shoeboxImageCalcVersion="v2-numba", the default). Selecting a serial generator degrades to materialized storage rather than failing. Two further consequences:

• images["atten_all"] (and the atten_all_early / atten_all_late pair) is absent in compact mode. Code that reads those arrays directly must set shoeboxCompactImages=0.
• The legacy Ray backend cannot consume compact storage and raises NotImplementedError. Use the numba backend (run_DEISM), which is the faster and supported path.

RTFs agree with materialized storage to ~1e-8 relative error for ORG, LC, and MIX, with real and complex impedance alike.

Convex rooms (DEISM-ARG)

For convex rooms the compact geometry is the wall sequence and incidence cosine per image.

Configuration (in the parameter dictionary / config):

• convexCompactImages (default 1): 0 selects the legacy path.
• convexCompactEngine (default "cpp"): which engine produces the compact geometry when compact mode is on — "cpp" (the libroom C++ extension) or "python" (Room_deism_python, the reference producer). The C++ engine is the default because it is faster at every band count measured and matches the Python producer exactly on wall sequences, to 1e-4 on incidence cosines and to 1e-5 end to end; select "python" when the extension cannot be built. Rebuild the extension after updating the sources: python setup.py build_ext --inplace.

Neither flag is read from the YAML configuration files or the command line — both are set programmatically on the parameter dictionary, e.g. deism.params["convexCompactImages"] = 0 to select the legacy path.

convexCompactEngine is ignored in legacy mode (convexCompactImages=0), which keeps the original C++ behavior with per-frequency attenuation computed in libroom.

Notes:

• Compact mode supports exactly one receiver per run (the standard DEISM-ARG setup). Multiple receivers raise an error.
• This DEISM-ARG compact path is 3D-only and applies to convex rooms. Shoebox rooms have their own compact storage, described above, selected with shoeboxCompactImages.
• Complex impedance is handled exactly in compact mode (the attenuation is rebuilt by _build_arg_attenuation_batch); the legacy C++ path truncates complex impedance to its real part — a known parity gap of order 1e-2.
• Compatible with the ORG, LC, and MIX DEISM variants and with ifRemoveDirectPath; output shapes are unchanged relative to legacy mode.
• Cross-engine agreement is implementation parity, not acoustic validation: the known DEISM-ARG limitations for arbitrary geometries (reflection- boundary discontinuities, missing spherical-wave reflection effects, edge/ corner diffraction) apply to all backends equally.