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Definition Functional Requirements Syntax Semantics Conformance Testing Performance Assessment

1 Definition

Acoustic Profile (CAE-ACP) is data describing the acoustic characteristics of an Object or of a Scene. The Acoustic Profile of an Object includes its frequency range, spectrogram, loudness and directional patterns; the Acoustic Profile of a Scene includes its reflectivity, reverberation, diffusion, absorption and Doppler effect.
It enables interoperable analysis, rendering, and interpretation of the acoustic properties of Objects and Scenes. A Data Type that refers to an Acoustic Profile refers to the one it has: the Object part or the Scene part.

2 Functional Requirements

The Acoustic Profile of an Object shall allow for representation of:

Frequency Characteristics

  • FrequencyRange
    • MinFrequencyHz: Minimum nominal frequency emitted or represented by the Object
    • MaxFrequencyHz: Maximum nominal frequency

Spectral Content

  • Spectrogram: Reference to OSD Plot describing frequency-dependent magnitude information.

Loudness

  • Loudness: Perceptual loudness measure (e.g., LUFS in dB).

Directional Characteristics

  • DirectionalPatterns: How the Object radiates by direction, relative to the orientation of its Space-Time (gain in dB by azimuth and elevation, optionally by frequency band).

The Acoustic Profile of a Scene shall allow for representation of:

Room-Interaction Characteristics

  • Reflectivity
    • EarlyReflectionTime (s)
    • LateReflectionTime (s)
  • Reverberation (frequency-dependent where applicable)
    • RT60: time for decay of 60 dB
    • RT30: decay of 30 dB
    • RT20: decay of 20 dB
    • EDT: early decay time
  • Diffusion: Schroeder Diffusion Coefficient (number ≥ 0)
  • Absorption: Absorption coefficient (number ≥ 0)
  • Doppler Effect: DirectSoundFactor (0 to 1) and IndirectSound (number ≥ 0), related to the velocity of the Audio Object.

3 Syntax

https://schemas.mpai.community/CAE3/V1.0/data/AcousticProfile.json

4 Semantics

Label Description
Header Acoustic Profile Header – standard CAE-ACP-Vx.y (the value “CAE-ACP-V1.0”). Both parts carry it.
MInstanceID Identifier of the M‑Instance producing or associated with this profile.
UEnvironmentID Identifier of the User Environment.
AcousticProfileID Identifier of this Acoustic Profile instance. Required.
AcousticProfileTime Time of this Acoustic Profile instance (Simple Time (OSD-STM)).
Object part The acoustics of an Object: what it sounds like, and how it radiates. Required: Header, AcousticProfileID, FrequencyRange, Loudness. The following fields are those of the Object part.
FrequencyRange Minimum and maximum nominal frequencies of the Object. Required.
• MinFrequencyHz Minimum frequency (Hz), a number not below 0. Required.
• MaxFrequencyHz Maximum frequency (Hz), a number not below 0. Required.
Spectrogram Plot (OSD-PLT) describing frequency-dependent amplitude data.
Loudness Perceptual loudness measure, a number (e.g., LUFS in dB). Required.
DirectionalPatterns How the Object radiates by direction, relative to the orientation of its Space-Time: gain in dB by azimuth and elevation (a 2D Plot (OSD-PLT)), or by azimuth, elevation and frequency band (a 3D Plot). Absent, the Object radiates alike in every direction.
DataXMData Data Exchange Metadata describing this Acoustic Profile instance.
DescrMetadata Optional human‑readable description (≤2048 characters).
Scene part The acoustics of a Scene: what happens to the sound of its Objects on the way to the listener. Required: Header, AcousticProfileID. The following fields are those of the Scene part.
Reflectivity[] Measures of reflection in the same medium.
• EarlyReflectionTime Early reflection arrival time (seconds), a number not below 0. Required.
• LateReflectionTime Late reflection arrival time (seconds), a number not below 0. Required.
Reverberation[] Persistence of sound after excitation.
• RT60 Frequency-dependent decay over 60 dB (Plot (OSD-PLT)).
• RT30 Decay over 30 dB (Plot (OSD-PLT)).
• RT20 Decay over 20 dB (Plot (OSD-PLT)).
• EDT Early decay time, a number not below 0.
Diffusion Degree of sound field diffusion (Schroeder coefficient), a number not below 0.
Absorption Absorption coefficient, a number not below 0.
Doppler[] Pitch-shifting effect.
• DirectSoundFactor Factor of the direct sound, a number from 0 to 1.
• IndirectSound The indirect sound, a number not below 0.
DataXMData Data Exchange Metadata describing this Acoustic Profile instance.
DescrMetadata Optional human‑readable description (≤2048 characters).

5 Conformance Testing

A Data instance Conforms with CAE-ASM V1.0 Acoustic Profile (CAE-ACP) if:

  1. Its JSON Object validates against its JSON Schema, as the Object part or as the Scene part.
  2. Any included JSON Object validates against its JSON Schema.
  3. All Data in the JSON Object:
    1. Have the specified Data Types.
    2. Conform with the Qualifiers signaled in their JSON Schemas.

6 Performance Assessment

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