## Distance-attenuation Extension

Version 3
*(Nils Peters, 07/05/2011 12:54 am)*

1 | 1 | Nils Peters | h1. Distance-attenuation Extension |
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3 | 1 | Nils Peters | Review of concepts for simulating distance attenuation of sound sources. |

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5 | 1 | Nils Peters | h2. MIDI Manufacturers Association, Interactive Audio Special Interest Group 3D Level 1 Guideline |

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7 | 1 | Nils Peters | source: http://www.midi.org/techspecs/rp49public.pdf |

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10 | 1 | Nils Peters | * Maximum Distance Parameter |

11 | 3 | Nils Peters | ** the distance at which no additional distance based attenuation is applied when the sound moves further away |

12 | 1 | Nils Peters | * Gain at Maximum Distance Parameter |

13 | 3 | Nils Peters | ** the maximum distance based attenuation applied to the sound. It is applied when the sound is at Maximum Distance |

14 | 1 | Nils Peters | * Reference Distance Ratio Parameter |

15 | 3 | Nils Peters | ** the distance beyond which distance based attenuation is applied, and below which no distance based attenuation is applied |

16 | 3 | Nils Peters | * Distance Ratio Parameter |

17 | 3 | Nils Peters | ** the normalized distance (0..1). the actual distance is computed by @distanceRatio@ * @maximumDistance@ |

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19 | 1 | Nils Peters | !spatial-midi.png! |

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21 | 3 | Nils Peters | The actual attenuation due to distance is computed according to the following model and is the same than the IA-SIG has chosen for the 3D Audio Rendering and Evaluation guidelines Level 2 (I3DL2). |

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23 | 2 | Nils Peters | @attenuation@ = 20*log10(@referenceDistance@ / (@referenceDistance@ + @ROF@ (@distance@ - @referenceDistance@))) |

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25 | 2 | Nils Peters | @ROF@, the roll-off factor is defined as: |

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27 | 2 | Nils Peters | @ROF@ = (@referenceDistance@ * 10^(- @maxAttenuation@ * 0.05) - @referenceDistance@) / (@maxDistance@ - @referenceDistance@) |

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