Infrasound and its relevance for audible sound

• Applicants: Dr.-Ing. Thomas Fedtke; Professor Dr. Jesko L. Verhey
• Subject Area: Acoustics ; Otolaryngology, Phoniatrics and Audiology
• Term: from 2017 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 381242260

• Final Report Year: 2023

Final Report Abstract

An increasing number of individuals are being exposed to infrasound. It is, however, still not clear, how infrasound is processed by human beings. It is well known that certain individuals may be particularly sensitive and that their quality of life is considerably degraded by a range of symptoms (insomnia, concentration disorders, restlessness, migraine). The project aimed at investigating the perception mechanisms for infrasound and low-frequency sound. The focus was on the perception of infrasound with the ear. One hypothesis, how infrasound can be heard, was that the auditory system generates audible distortion products in the audiofrequency range. In order to investigate this hypothesis, it was crucial to rule out that these distortions are produced technically, i.e., by the infrasound stimulus presentation devices. Therefore, the project started with developing both, distortion-free infrasound sources and sensitive ear canal sound measuring devices. The latter was used in vivo to quantify the harmonic distortion produced by the human auditory system. It was investigated if the individual threshold in quiet correlate with the distortions. The results do not support the hypothesis of the audibility of infrasound on the basis of distortions. An alternative infrasound perception hypothesis is that infrasound becomes audible because it modulates audio sounds. In psychoacoustic experiments, infrasound had an impact on the perception of an amplitude modulation in the audio-frequency range, supporting the hypothesis. Apart from the testing of these hypotheses, general characteristics of infrasound perception with respect to temporal and spectral integration were investigated. The results of the latter as well as the technical ear-canal sound measurements were used as the basis for developing models of the infrasound perception processes within this project. The results of this project are believed to lay, in the long run, the ground for future safety regulations and for an adequate characterization of infrasound emission. The results are important for both protection of health (protection against hazardous infrasound immission) and economic development (infrasound emission, e.g., manufacturers and operators of wind turbines).

Publications

• Kompaktes verzerrungsarmes Infraschall-Einsteckhörersystem. Vortrag, 45. Jahrestagung für Akustik, DAGA 2019, Rostock. (2019)
  Joost H., Friedrich B., Verhey J. L. & Fedtke T.
  
• Detektionsschwellen von Infraschall-Tonkomplexen. Tagungsband der 46. Jahrestagung für Akustik, DAGA 2020, Hannover. (2020)
  Friedrich B., Joost H., Fedtke T. & Verhey J. L.
  
• Is infrasound perceived by the auditory system through distortions?. Acta Acustica, 5, 4.
  Joost, Holger; Friedrich, Björn; Verhey, Jesko L. & Fedtke, Thomas
  
• Spectral integration of infrasound at threshold. The Journal of the Acoustical Society of America, 147(3), EL259-EL263.
  Friedrich, Björn; Joost, Holger; Fedtke, Thomas & Verhey, Jesko L.
  
• Ein Modell zur Zeitintegration akustischer Reize im Infraschallbereich. Tagungsband der 47. Jahrestagung für Akustik, DAGA 2021, Wien. (2021)
  Friedrich B., Joost H., Fedtke T. & Verhey J. L.
  
• Schutz des Gehörs bei Infraschall-Hörversuchen. Tagungsband der 47. Jahrestagung für Akustik, DAGA 2021, Wien. (2021)
  Joost H., Bug M., Friedrich B., Verhey J. L. & Fedtke T.
  
• Zur Kalibrierung von Einsteckhörern für Infraschall und tieffrequenten Hörschall: Real-Ear-to-Coupler Differences (RECD). Vortrag, 24. Jahrestagung der Deutschen Gesellschaft für Audiologie, DGA 2022, Erfurt.Friedrich B, Joost H, Fedtke T, Verhey JL (2022) Daten zur Zeitintegration akustischer Reize im Infraschallbereich. Tagungsband der 48. Jahrestagung für Akustik, DAGA 2022, Stuttgart.
  Joost H., Friedrich B., Verhey J. L. & Fedtke T.
  
• Effects of infrasound on the perception of a low-frequency sound. Acta Acustica, 7(2023), 60.
  Friedrich, Björn; Joost, Holger; Fedtke, Thomas & Verhey, Jesko L.
  
• Einfluss des Infraschalls auf die Wahrnehmung von Amplitudenmodulationen im Hörfrequenzbereich. Tagungsband der 49. Jahrestagung für Akustik, DAGA 2023, Hamburg.
  Friedrich B., Joost H., Fedtke T. & Verhey J. L.
  
• How to define thresholds for level and interaural-level-difference discrimination: Insights from scedasticities and distributions. Hearing Research, 436, 108837.
  Heil, Peter & Friedrich, Björn
  
• Temporal integration of infrasound at threshold. PLOS ONE, 18(7), e0289216.
  Friedrich, Björn; Joost, Holger; Fedtke, Thomas & Verhey, Jesko L.