{ "title": "Describe time, space and acoustic response — Virtual Acoustic Objects", "text": "MODAVIS (2026). Describe time, space and acoustic response — Virtual Acoustic Objects. Research notebooks, September 2026 · research guides edition. https://modavis.org/editions/2026-09-r4/vao/acoustics/", "bibtex": "@misc{modavis_vao_acoustics_2026_09_r4,\n author = {{MODAVIS}},\n title = {Describe time, space and acoustic response — Virtual Acoustic Objects},\n year = {2026},\n month = {09},\n version = {2026-09-r4},\n url = {https://modavis.org/editions/2026-09-r4/vao/acoustics/},\n note = {Content SHA-256: 4bb7e2d2e00c69506d2dbec85cfa61b2f3414f3842f8e260fae7fc0edb833036}\n}", "url": "https://modavis.org/editions/2026-09-r4/vao/acoustics/", "sha256": "4bb7e2d2e00c69506d2dbec85cfa61b2f3414f3842f8e260fae7fc0edb833036", "edition": "2026-09-r4", "date": "2026-09-26", "canonicalPayload": "{\"book\":{\"number\":\"01\",\"slug\":\"vao\",\"title\":\"Virtual Acoustic Objects\"},\"chapter\":{\"blocks\":[{\"id\":\"timebases\",\"text\":\"A shared timeline needs an explicit mapping\",\"type\":\"heading\"},{\"text\":\"Audio frames, video frames, MIDI events and animation ticks do not automatically share a clock. VAO 0.5.0 describes explicit timebases and mappings. Rational rates avoid ambiguous decimal approximations; half-open intervals include their start and exclude their end. A region from frame 0 to frame 48,000 at 48,000 frames per second is therefore one second long, without counting an extra endpoint sample.\",\"type\":\"p\"},{\"text\":\"A linear mapping relates coordinates as target = source × scale + offset. Both coordinate units matter. For a source measured in audio frames and a target measured in seconds, the scale has units of seconds per frame. Clock drift, residual uncertainty and discontinuities require their own treatment. A single offset can align an onset without explaining drift during a long session, and a mapping must not interpolate across an unmodeled dropout.\",\"type\":\"p\"},{\"label\":\"Illustrative timing calculation · explanatory notation, not a VAO JSON record\",\"text\":\"source coordinate: audio frame index at 48,000 frames/second\\ntarget coordinate: video time in seconds\\nscale = 1 / 48,000 seconds/frame\\noffset = 0.125 seconds\\nframe 96,000 maps to 2.125 seconds\\n\\nKeep the measured alignment uncertainty and any discontinuities separately.\",\"type\":\"code\"},{\"id\":\"spatial-frames\",\"text\":\"A position means something within a frame\",\"type\":\"heading\"},{\"text\":\"A coordinate triple is incomplete without units, axis definitions, handedness and a reference frame. A microphone pose in an instrument frame differs from its pose in a room frame. A geographic longitude and latitude pair must not be silently interpreted as local Cartesian x and y. Explicit transformations and their provenance let another client reconstruct the intended relations or identify a missing conversion.\",\"type\":\"p\"},{\"text\":\"For a measured response, preserve the source and receiver positions, orientations where relevant, instrument and room state, and the method used to establish them. An approximate position should remain approximate. Giving more decimal places to an estimated coordinate does not improve the underlying measurement. A change of coordinate frame is a transformation; it is not a new acoustic observation.\",\"type\":\"p\"},{\"id\":\"impulse-responses\",\"text\":\"Keep the response and its domain together\",\"type\":\"heading\"},{\"text\":\"An impulse response characterizes a specified source–receiver arrangement under particular conditions. Its association with a VAO should identify the exact signal realization, channel interpretation and the scene or measurement to which it belongs. Applying that response elsewhere is a modeling choice. A player needs an explicit policy for positions outside the measured or modeled domain, such as a declared fallback, instead of suggesting that one response captures every listening position.\",\"type\":\"p\"},{\"headers\":[\"Record\",\"What the reader needs\",\"What it does not establish alone\"],\"rows\":[[\"Captured response\",\"Measurement setup, positions, signal identity and processing lineage.\",\"Validity at every source and receiver position.\"],[\"Simulated response\",\"Geometry, material and boundary assumptions, method and evaluation evidence.\",\"A measured response of the historical room.\"],[\"Acoustic metric\",\"Quantity, unit, band axes, method, uncertainty and any cited standard edition.\",\"Conformance merely because a standard is named.\"],[\"Learned field or surrogate\",\"Training and validation evidence, supported domain and derivation.\",\"Reliable extrapolation to undocumented conditions.\"]],\"type\":\"table\"},{\"id\":\"profiles\",\"text\":\"Declare the capabilities the object actually uses\",\"type\":\"heading\"},{\"text\":\"VAO 0.5.0 requires Core and Dynamic Delivery for every conforming object, including an embedded-only package. Additional profiles follow the represented capabilities: Multimodal Timeline for timebases and synchronized tracks, Spatial for frames and poses, Acoustics for relevant response or scene records, and Scientific for scientific records. Physical Instrument, Playable and Deterministic Runtime address further aspects when present. Profile declarations are not a promise that every client will execute every feature.\",\"type\":\"p\"},{\"text\":\"A useful inspection sequence is to read the profile declarations, identify required materialization groups, verify their availability, and then check the application’s implementation scope. A Blender importer may inspect a spatial package and load geometry without executing its acoustic behavior. A runtime capable of convolution still needs the correct responses, mappings and dependencies. The object contract and the application capability are both necessary to interpret what the user hears.\",\"type\":\"p\"},{\"items\":[{\"detail\":\"Inspection, geometry import, audio and interactive execution.\",\"href\":\"/notebooks/software/clients/\",\"label\":\"Compare VAO clients\"},{\"detail\":\"Preserve regions, channels and acquisition context.\",\"href\":\"/notebooks/fieldwork/analysis/\",\"label\":\"Connect a recording to its analysis\"}],\"type\":\"links\"}],\"intro\":\"An audio file becomes scientific evidence through its relationships: to an instrument state, a clock, a measurement position, a room and a processing history.\",\"slug\":\"acoustics\",\"sources\":[{\"detail\":\"Normative standard, profile index, Dynamic Delivery Profile and conformance specification in the versioned release.\",\"href\":\"https://doi.org/10.5281/zenodo.22214248\",\"label\":\"VAO Standard 0.5.0\"},{\"detail\":\"Dissertation submitted to Universität Leipzig, 11 September 2026. Chapters 5 and 6; evaluation distinctions in §8.1.1, pp. 254–256. Page numbers refer to the printed manuscript pagination. The manuscript is not distributed by this website.\",\"label\":\"Dominik Ukolov · Musikinstrumente im virtuellen Raum (2026)\"}],\"title\":\"Describe time, space and acoustic response\"},\"date\":\"2026-09-26\",\"edition\":\"2026-09-r4\",\"figures\":{}}", "payload": { "edition": "2026-09-r4", "date": "2026-09-26", "book": { "slug": "vao", "title": "Virtual Acoustic Objects", "number": "01" }, "chapter": { "slug": "acoustics", "title": "Describe time, space and acoustic response", "intro": "An audio file becomes scientific evidence through its relationships: to an instrument state, a clock, a measurement position, a room and a processing history.", "blocks": [ { "type": "heading", "id": "timebases", "text": "A shared timeline needs an explicit mapping" }, { "type": "p", "text": "Audio frames, video frames, MIDI events and animation ticks do not automatically share a clock. VAO 0.5.0 describes explicit timebases and mappings. Rational rates avoid ambiguous decimal approximations; half-open intervals include their start and exclude their end. A region from frame 0 to frame 48,000 at 48,000 frames per second is therefore one second long, without counting an extra endpoint sample." }, { "type": "p", "text": "A linear mapping relates coordinates as target = source × scale + offset. Both coordinate units matter. For a source measured in audio frames and a target measured in seconds, the scale has units of seconds per frame. Clock drift, residual uncertainty and discontinuities require their own treatment. A single offset can align an onset without explaining drift during a long session, and a mapping must not interpolate across an unmodeled dropout." }, { "type": "code", "label": "Illustrative timing calculation · explanatory notation, not a VAO JSON record", "text": "source coordinate: audio frame index at 48,000 frames/second\ntarget coordinate: video time in seconds\nscale = 1 / 48,000 seconds/frame\noffset = 0.125 seconds\nframe 96,000 maps to 2.125 seconds\n\nKeep the measured alignment uncertainty and any discontinuities separately." }, { "type": "heading", "id": "spatial-frames", "text": "A position means something within a frame" }, { "type": "p", "text": "A coordinate triple is incomplete without units, axis definitions, handedness and a reference frame. A microphone pose in an instrument frame differs from its pose in a room frame. A geographic longitude and latitude pair must not be silently interpreted as local Cartesian x and y. Explicit transformations and their provenance let another client reconstruct the intended relations or identify a missing conversion." }, { "type": "p", "text": "For a measured response, preserve the source and receiver positions, orientations where relevant, instrument and room state, and the method used to establish them. An approximate position should remain approximate. Giving more decimal places to an estimated coordinate does not improve the underlying measurement. A change of coordinate frame is a transformation; it is not a new acoustic observation." }, { "type": "heading", "id": "impulse-responses", "text": "Keep the response and its domain together" }, { "type": "p", "text": "An impulse response characterizes a specified source–receiver arrangement under particular conditions. Its association with a VAO should identify the exact signal realization, channel interpretation and the scene or measurement to which it belongs. Applying that response elsewhere is a modeling choice. A player needs an explicit policy for positions outside the measured or modeled domain, such as a declared fallback, instead of suggesting that one response captures every listening position." }, { "type": "table", "headers": [ "Record", "What the reader needs", "What it does not establish alone" ], "rows": [ [ "Captured response", "Measurement setup, positions, signal identity and processing lineage.", "Validity at every source and receiver position." ], [ "Simulated response", "Geometry, material and boundary assumptions, method and evaluation evidence.", "A measured response of the historical room." ], [ "Acoustic metric", "Quantity, unit, band axes, method, uncertainty and any cited standard edition.", "Conformance merely because a standard is named." ], [ "Learned field or surrogate", "Training and validation evidence, supported domain and derivation.", "Reliable extrapolation to undocumented conditions." ] ] }, { "type": "heading", "id": "profiles", "text": "Declare the capabilities the object actually uses" }, { "type": "p", "text": "VAO 0.5.0 requires Core and Dynamic Delivery for every conforming object, including an embedded-only package. Additional profiles follow the represented capabilities: Multimodal Timeline for timebases and synchronized tracks, Spatial for frames and poses, Acoustics for relevant response or scene records, and Scientific for scientific records. Physical Instrument, Playable and Deterministic Runtime address further aspects when present. Profile declarations are not a promise that every client will execute every feature." }, { "type": "p", "text": "A useful inspection sequence is to read the profile declarations, identify required materialization groups, verify their availability, and then check the application’s implementation scope. A Blender importer may inspect a spatial package and load geometry without executing its acoustic behavior. A runtime capable of convolution still needs the correct responses, mappings and dependencies. The object contract and the application capability are both necessary to interpret what the user hears." }, { "type": "links", "items": [ { "label": "Compare VAO clients", "href": "/notebooks/software/clients/", "detail": "Inspection, geometry import, audio and interactive execution." }, { "label": "Connect a recording to its analysis", "href": "/notebooks/fieldwork/analysis/", "detail": "Preserve regions, channels and acquisition context." } ] } ], "sources": [ { "label": "VAO Standard 0.5.0", "href": "https://doi.org/10.5281/zenodo.22214248", "detail": "Normative standard, profile index, Dynamic Delivery Profile and conformance specification in the versioned release." }, { "label": "Dominik Ukolov · Musikinstrumente im virtuellen Raum (2026)", "detail": "Dissertation submitted to Universität Leipzig, 11 September 2026. Chapters 5 and 6; evaluation distinctions in §8.1.1, pp. 254–256. Page numbers refer to the printed manuscript pagination. The manuscript is not distributed by this website." } ] }, "figures": {} } }