1     Definition 2     Functional Requirements 3     Syntax
4     Semantics 5    Conformance Testing 6     Performance Assessment

1    Definition

Acoustic Profile is data describing the intrinsic acoustic characteristics of an object.
It includes spectral, temporal, and room‑interaction descriptors, enabling interoperable analysis, rendering, and interpretation of object‑level audio properties.

2     Functional Requirements

The Acoustic Profile shall allow for representation of:

Frequency Characteristics

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

Timbre Characteristics

  1. MFCC (Mel‑frequency cepstral coefficients)
  2. SpectralCentroid (Hz)
  3. OtherDescriptors (object containing additional named spectral features)

Spectral Content

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

Loudness

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

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 (ms or seconds depending on calibration)
  • Diffusion: Schroeder Diffusion Coefficient (number ≥ 0)
  • Absorption: Absorption coefficient, 0 ≤ value ≤ 1
  • Doppler Effect: Related top the velocity of the Audio Object.

3     Syntax

https://schemas.mpai.community/OSD/V1.5/data/AcousticProfile.json

4     Semantics

Label Description
Header Acoustic Profile Header – standard OSD-ACP-Vx.y
MInstanceID Identifier of the M‑Instance producing or associated with this profile
AcousticProfileID Identifier of this Acoustic Profile instance
FrequencyRange Minimum and maximum nominal frequencies of the object
• MinFrequencyHz Minimum frequency (Hz)
• MaxFrequencyHz Maximum frequency (Hz)
Timbre Exactly one timbral characterization option:
• MFCC Array of Mel-frequency cepstral coefficients
• SpectralCentroid Spectral centroid in Hz
• OtherDescriptors Object containing additional named timbral descriptors (numeric values)
Spectrum OSD Plot describing frequency-dependent amplitude data
Loudness Perceptual loudness measure (LUFS or dB SPL)
Reflectivity Measures of reflection in the same medium
• EarlyReflectionTime Early reflection arrival time (seconds)
• LateReflectionTime Late reflection arrival time (seconds)
Reverberation Persistence of sound after excitation
• RT60 Frequency-dependent decay over 60 dB
• RT30 Decay over 30 dB
• RT20 Decay over 20 dB
• EDT Early decay time to −10 dB
Diffusion Degree of sound field diffusion (Schroeder coefficient)
Absorption Absorption coefficient (0–1)
Doppler Pitch-shifting effect.
  – Direct Sound Factor Number greater than or equal to 0
  – Indirect Sound Factor Number greater than or equal to 0
OACRights Per‑property rights (optional)
Rights Rights governing usage of the entire Acoustic Profile
DataExchangeMetadata Metadata for regulated interoperability scenarios
Trace Provenance metadata (Source, Time) per AIF V3.0
DescrMetadata Optional human‑readable description (≤2048 characters)

5     Conformance Testing

A Data instance Conforms with Acoustic Profile (OSD-ACP) if:

  1. Its JSON Object validates against its JSON Schema.
  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