Transfer Function Measurements When the Reference Signal is Known but not Accessible

Metadata

Publisher: SMPTE
Doc Type: Journal Article
Content Type: Original Research
Abbreviated Title: SMPTE Motion Imaging Jour.
Volume: 134, No. 3, pp. 16–21
Abstract: Transfer function measurements offer significant benefits over historical band spectrum measurements for calibrating loudspeakers by additionally calculating phase and coherence in the frequency domain and identifying the arrival time of reflections in the time domain. However, this requires two channels: the reference signal input to the speaker and a microphone in the sound field. In cinema systems, it is often difficult to duplicate the reference signal to an analyzer. There may be no spare inputs or outputs, limited routing options, and/or digital connectors not conducive to a Y-cable. A virtual reference method is presented, which, given a copy of the reference signal, can be reconstituted in real-time. Virtual reference can also detect, measure, and compensate for sample rate differences between the playback device and the analyzer. This allows the analyzer to show a stable trace while virtual reference separately displays clocking differences such as jitter and wander.
Publication Date: 2025-05-01
DOI: 10.5594/JMI.2025/PGRJ7276
ISSN: Print: 1545-0279 | Electronic: 2160-2492
Link: https://doi.org/10.5594/JMI.2025/PGRJ7276
Author(s): Juan Sierra Lozanzo
Swapan Gandhi
Jay Wyatt
Roger Schwenke
Keyword(s): Transfer Function, Reference Signal, Virtual Reference, Band Spectrum
Copyright: © 2025 SMPTE

Bibliographic Reference(s)

AES3-3-2009 (r2024) [Active, Reaffirmed]
AES75.2023 — Audio Engineering Society (AES), AES75-2023, “AES Standard for Acoustics-Measuring loudspeaker maximum linear sound levels using noise.”. EXTERNAL
ISO.226.2023 — International Organization for Standardization (ISO) ISO 226:2023, “Acoustics—Normal equal-loudness-level contours.”. EXTERNAL
John Meyer, “Precision Transfer Function Measurements Using Program Material as the Excitation Signal,” Proc. 111th International AES, p. 354, 2001. EXTERNAL
Audiovisual and Integrated Experience Association (AVIXA), A103.01:2019, “Sound System Spectral Balance.”. EXTERNAL
R. Schwenke and B. Long, “Physiological and Psycho-Acoustic basis for Multi-Resolution Frequency Response Analysis,” presented at the SMPTE 2011 Annual Tech. Conf. & Exhibit., Hollywood, CA, Oct. 2011. EXTERNAL
J. Bendat and A. Piersol, Random Data Analysis and Measurement Procedures, John Wiley & Sons, New York, 1986. EXTERNAL
R. Schwenke and M. Van Veen, “Determining the Source of Coherence Reduction using Playback Level of M-Noise,” presented at Reproduced Sound 2020, Institute of Acoustics (IOA), U.K., 2020. EXTERNAL
R. G. Klumpp and H. R. Eady, “Some Measurements of Interaural Time Difference Thresholds,” J. Acoust. Soc. Am., 28(5): 859–860, Sep. 1956. EXTERNAL
S. Thavam and M. Dietz, “Smallest Perceivable Interaural Time Differences,” J. Acoust. Soc. Am., 145(1): 458–468, Jan. 2019. EXTERNAL
SMPTE ST 202:2010 [Active, Stabilized]

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Juan Sierra Lozanzo, Swapan Gandhi, Jay Wyatt, and Roger Schwenke; Transfer Function Measurements When the Reference Signal is Known but not Accessible, MIJ 2025, Volume 134, Number 3 (pp. 16 to 21); SMPTE, 2025. Available at https://doi.org/10.5594/JMI.2025/PGRJ7276

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Juan Sierra Lozanzo, Swapan Gandhi, Jay Wyatt, and Roger Schwenke; Transfer Function Measurements When the Reference Signal is Known but not Accessible, MIJ 2025, Volume 134, Number 3 (pp. 16 to 21); SMPTE, 2025. Available at https://doi.org/10.5594/JMI.2025/PGRJ7276

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<span class="citation">Juan Sierra Lozanzo, Swapan Gandhi, Jay Wyatt, and Roger Schwenke; <cite>Transfer Function Measurements When the Reference Signal is Known but not Accessible</cite>, MIJ 2025, Volume 134, Number 3 (pp. 16 to 21); SMPTE, 2025. Available at <a href="https://doi.org/10.5594/JMI.2025/PGRJ7276" target="_blank" rel="noopener">https://doi.org/10.5594/JMI.2025/PGRJ7276</a></span>

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Juan Sierra Lozanzo, Swapan Gandhi, Jay Wyatt, and Roger Schwenke; Transfer Function Measurements When the Reference Signal is Known but not Accessible, MIJ 2025, Volume 134, Number 3 (pp. 16 to 21); SMPTE, 2025
doi: 10.5594/JMI.2025/PGRJ7276
url: https://doi.org/10.5594/JMI.2025/PGRJ7276

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<li>
Juan Sierra Lozanzo, Swapan Gandhi, Jay Wyatt, and Roger Schwenke; <cite id="bib-10-5594-jmi-2025-pgrj7276">Transfer Function Measurements When the Reference Signal is Known but not Accessible</cite>, MIJ 2025, Volume 134, Number 3 (pp. 16 to 21); SMPTE, 2025
<span class="doi">10.5594/JMI.2025/PGRJ7276</span>
</li>