State primary standard of sound pressure unit in air and audiometric scales GET 19-2025

The issues of calibration of sound pressure measuring instruments in the air (measuring microphones, sound level meters, etc.) are considered. At free-field calibration of measuring devices by a secondary method (by comparison with a reference measuring microphone), one of the sources of error is the determination of the free-field sensitivity of a reference microphone, defi ned as the sum of its pressure sensitivity and the typical diffraction correction. This approach to determining the free field sensitivity of a reference microphone was used due to the absence in the Russian Federation of a standard that implements the free-field calibration of measuring microphones by primary method and due to dependence on foreign acoustic laboratories, which are the source of data on typical diffraction corrections for measuring microphones. As part of the course to ensure the technological sovereignty of the Russian Federation in key areas of measurement and to ensure the transfer of the unit of sound pressure in air with high accuracy to measuring instruments intended for use in free-field conditions, the State Primary Standard of the unit of sound pressure in air and audiometric scales GET 19-2018 was improved with the aim of implementing the free-field calibration of measuring microphones using the primary method. The free-field calibration of measuring microphones is implemented using the reference anechoic chamber built at VNIIFTRI and Russian-made measuring equipment, which together form the reference complex EK-SP, included in the State Primary Standard of the unit of sound pressure in air and audiometric scales GET 19-2025. GET 19-2025 provides a free-fi eld calibration frequency range of 1–25 kHz with an unexcluded systematic error within 0.07–0.15 dB depending on the frequency, and the standard deviation of the result of 10 measurements is 0.02–0.1 dB depending on the frequency. Improving the accuracy of measurements in a free sound field is important for the aviation and engine industries, the rocket and space industry, transport, communications, ecology and healthcare.

1. Aslanyan E. G., Balahanov M. V., Dobrovolskii V. I., Kovalenko O. I., Nekrasov V. N. Physical and technical measurements at VNIIFTRI. Development prospects. Al’manac of modern metrology, (4(20)), 11–30 (2019). (In Russ.) https://www.elibrary.ru/ctpccn

2. Kon’kov A. V., Kuznetsov S. V., Kolesov S. Yu. Metrological Characteristics of the National Primary Standard for the Unit of Acoustic Pressure in Air at Frequencies of 2–25·103 Hz GET 19-2010. Izmeritel’naya Tekhnika, (4), 5–8 (2017). (In Russ.) https://www.elibrary.ru/yqiiiz

3. Wagner R. P., Nedzelnitsky V. Determination of acoustic center correction values for type LS2aP microphones at normal incidence. Journal of the Acoustical Society of America, 104(1), 192–203 (1998). https://doi.org/10.1121/1.423288

4. Jacobsen F., Barrera Figueroa S., Rasmussen K. A note on the concept of acoustic center. Journal of the Acoustical Society of America, 115(4), 1468–1473 (2004). https://doi.org/10.1121/1.1652036

5. Barrera-Figueroa S., Rasmussen K., Jacobsen F. The acoustic center of laboratory standard microphones. Journal of the Acoustical Society of America, 120(5), 2668–2675 (2006). https://doi.org/10.1121/1.2345830

6. Rodrigues D., Durocher J.-N., Bruneau M., Bruneau A.-M. A new method for the determination of the acoustic center of acoustic transducers. Acta Acustica, 96(2), 300–305 (2010). https://doi.org/10.3813/AAA.918279

7. Frederiksen E., Gramtorp J. Measurements of microphone free-field corrections and determination of their uncertainties. Bruel&Kjaer Technical Review, 1, 9–18 (1996). https://www.bksv.com/media/doc/bv0048.pdf

8. Barrera-Figueroa S., Rasmussen K., Jacobsen F. On experimental determination of the free-field correction of laboratory standard microphones at normal incidence. Metrologia, 44(1), 57–63 (2007). https://doi.org/10.1088/0026-1394/44/1/008

9. Golovin D. V., Vydrin Y. V., Vyshnyakov A. N., Nakvasin A. Y. Experimental studies to determine free-field corrections to the frequency characteristics of microphones used in aircraft noise testing on the ground. Proc. conference “XXI Scientific and Technical Conference on Aeroacoustics”, Moscow, September 21–26, 2025, pp. 232–233. TsAGI Publ., Moscow (2025). (In Russ.) https://www.elibrary.ru/bhsikh

10. Vishnyakov A. N., Golovin D. V. Generation of a test signal for calibration of ls microphones by the reciprocity method in a free field. Proc. conference “Digital signal processing and its application DSPA-2023”, Moscow, March 29–31, 2023, pp. 423–426. The Russian Scientific & Technical A. S. Popov Society for Radio Engineering, Electronics & Communications, Moscow (2023). (In Russ.) https://www.elibrary.ru/pbhabx

11. Barrera-Figueroa S., Rasmussen K., Jacobsen F. A time-selective technique for free-field reciprocity calibration of condenser microphones. Journal of the Acoustical Society of America, 114(3), 1467–1476 (2003). https://doi.org/10.1121/1.1604123

12. Hyu-Sang Kwon, Wan-Ho Cho, Sang-Joon Suh. Time-selective windowing technique in free-field microphone reciprocity calibration. Journal of the Acoustical Society of America, 134(1), 237–245 (2013). https://doi.org/10.1121/1.4809651

13. Isaev A. E. Precise calibration of sound pressure receivers in an aquatic environment under free field conditions. VNIIFTRI, Mendeleevo (2008). (In Russ.) https://www.elibrary.ru/shjlil

14. Denny Hermawanto, Kenji Ishikawa, Kohei Yatabe, Yasuhiro Oikawa. Determination of microphone acoustic center from sound field projection measured by optical interferometry. Journal of the Acoustical Society of America, 153(2), 1138–1146 (2023). https://doi.org/10.1121/10.0017246 ; https://elibrary.ru/pddgyt