The Impact of Psychoacoustics on Medical Diagnosis and Technology

By Anthoni Oisin, BScReviewed by Danielle Ellis, B.Sc.

What is Psychoacoustics?
Enhancing fetal heartbeat detection
Pulse oximetry with a psychoacoustic twist
Telehealth cochlear implant fittings
Listening for clues: Psychoacoustics in medical diagnosis
The future of sound in medicine
Conclusion
References
Further reading

What is Psychoacoustics?

Psychoacoustics is the study of sound perception and audiology¹. It is a branch of psychology associated with psychophysics, cognitive psychology, and neuroscience².

When applied, psychoacoustics offers insight into a wide range of disciplines, including acoustics, computer science, music, sound technologies, audio engineering, and more. ³ Research breakthroughs also suggest that psychoacoustics could be key in innovating medical technologies. ^,4,5,6

Enhancing fetal heartbeat detection

Fetal heartbeat detection is typically done using imaging technologies, such as the Doppler, vaginal ultrasound, and phonocardiography. ^4,7 Fetal phonocardiogram signals can be captured using the Doppler and digital stethoscopes in tandem with neural network systems. ⁸

Heart rate and heart rate variability can be strong indicators of fetal health, meaning heartbeat detection plays a significant role when monitoring pregnancies. ⁸ Moreover, regular fetal health monitoring is immensely important in high-risk pregnancies. ⁸

Phonocardiography plots the sounds made by heart contractions and other cardiac features. ⁴ Phonocardiograms are non-invasive for the patient while being cost-efficient, meaning they can be a useful tool. ⁴ Despite this, phonocardiograms can capture a great deal of noise, making them more difficult and less reliable to interpret. ⁴

Research from 2024 found that pitch-shifting can improve parts of phonocardiography that are relevant for the automatic detection of fetal heartbeats. ⁴ Over 200 features were extracted from phonocardiograms, including psychoacoustic and audio features. ⁴ These features were then analyzed and used to train algorithms. ⁴

Psychoacoustic features taken from pitch-shifted phonocardiograms were found to be useful for heartbeat detection in this study. ⁴ When applied to real-world data, automatic heartbeat detection accuracy increased by around 7%.⁴ When the process was applied to a simulated dataset, the accuracy also improved, although by a lower figure of around 4-5%.⁴ Similarly, the misclassification rate in simulated data decreased by up to a factor of three. ⁴

Pulse oximetry with a psychoacoustic twist

Pulse oximetry is a fast, non-invasive measure of the blood's oxygen saturation. ^9,10 Light is sent through finger tissue to assess how well oxygen is circulating in the body. ¹⁰ It is commonly used in care with many patients, including in busy or emergency settings. ^5,11

The Rise of Remote Pulse Oximeters

Anesthesiologists use pulse oximetry to assess several aspects of patient well-being, including oxygen saturation, heart rate regularity, and distal perfusion. ⁵ Specifically, pulse oximetry can provide significant auditory clues when monitoring oxygen saturation, which can be useful for monitoring patients in busy environments. ^5,11 Most oximeters use a variable-pitch pulse tone to provide clinicians with this information. ¹¹

The variable-pitch pulse tone is supposed to vary, creating an audio representation of the patient's oxygen saturation. ¹¹ However, research indicates that the acoustic properties of these tones are not standardized, potentially making it harder for clinicians to use the monitor meaningfully. ¹¹ As such, some argue that this should be redesigned for ease. ^{12, 13}

One suggestion to improve the tone was to use a combination of sonification and a Shepard tone. ¹³ The Shepard tone is an auditory illusion where a sound appears to increase or decrease pitch despite never changing continuously.¹⁴ When the tone was tested in a lab setting, participants could correctly identify the oxygen saturation in 84% of all cases, suggesting that there could be merit to this redesign. ¹³

Telehealth cochlear implant fittings

Cochlear implants are devices that can be fitted for hearing loss. ¹⁵ The implant transduces acoustic energy into electrical signals, stimulating cells in the auditory nerve. ¹⁵ They typically need to be surgically implanted in an outpatient setting. ¹⁵

A 2020 study tested the possibility of autonomous cochlear implant fittings using a combination of artificial intelligence, psychoacoustic self-tests, and in-clinic sessions. ⁶ Six adult patients were fitted with the implants in a clinical environment. ⁶ Two weeks later, they attended the clinic again to participate in a supervised self-fitting session that emulated a home environment. ⁶

Each patient performed two psychoacoustic tests on themselves at home: pure tone audiometry and spectral discrimination. ⁶ The results of these tests were analyzed by software that would recommend new mappings. ⁶ Ultimately, four out of six patients could perform the tests without support and were fitted by the application without manual intervention. ⁶

Some populations particularly benefit from at-home telehealth interventions. ^16,17 Those in rural areas may have difficulties accessing clinics or hospitals - particularly if specialist care, such as an audiologist, is required. ¹⁷ Similarly, individuals who are bedbound, housebound, or with chronic health conditions can benefit from remote access. ¹⁶ Decreasing the amount of time in the clinic for cochlear implants could help these groups. ⁶

Listening for clues: Psychoacoustics in medical diagnosis

Psychoacoustic assessment can be used when diagnosing various medical conditions. For example, tinnitus and hyperacusis - two conditions relating to sound and perception - can both be diagnosed using findings from psychoacoustics. ^,18,19 Acoustics has also been used to identify respiratory and cardiovascular conditions, such as COVID-19. ²⁰

Tinnitus occurs when someone hears sounds from inside the body, such as ringing, rumbling, or pulsating. ²¹ Tinnitus is diagnosed based on self-report, but psychoacoustic measurements could help to make diagnosis more robust and reliable. ¹⁸ Research suggests that loudness and pitch are both relevant to diagnosis. ¹⁸ Specifically, psychoacoustic loudness match tests are sensitive to the presence of tinnitus in a patient. ¹⁸

Hyperacusis can also be diagnosed with psychoacoustics. ¹⁹ People with hyperacusis experience heightened sensitivity to sound to the point where it can trigger pain. ¹⁹ A new method for diagnosing hyperacusis was proposed in 2021 based on rating sounds by preference. ¹⁹

The psychoacoustic test was comparably accurate to other pre-existing tests, like the Hyperacusis Questionnaire. ¹⁹ Additionally, the test offered a relatively comfortable patient experience, as diagnostic information was gathered even at levels below the defined loudness discomfort level. ¹⁹

The future of sound in medicine

Psychoacoustics has contributed to the medical field so far and could continue to do so with time. As many of the links between fields outlined so far relate to emergent techniques and technology, there is scope for their continued improvement and innovation.

Numerous other papers and proposals exist at the cross-section of psychoacoustics and medicine, such as sonification for surgical interventions, de-noising algorithms for analyzing bowel sounds, and improving nurses' cardiac auscultation proficiency. ^22,23,24 In time, more connections between the disciplines could emerge.

While psychoacoustics has already contributed a great deal to medical innovation, many of these technologies and tools still need to be finalized. Additional research and more interdisciplinary collaboration could help bolster the field further.

Conclusion

Psychoacoustics has substantially informed the development of medical technologies and diagnostics. Its direct impact can be seen in obstetrics, telemedicine, and beyond. The discipline's impact is notable not only in anticipated areas (like audiology) but also in the development of key medical tools.

Along with psychoacoustics' direct effects, it also influences the innovation and invention of tools used by clinicians across a range of specialisms. With more research, the field could continue to support progress in medical development.

References

1. Lin, Y., & Abdulla, W. H., (2015). Principles of psychoacoustics. Audio Watermark: A Comprehensive Foundation Using MATLAB, 15-49. https://link.springer.com/chapter/10.1007/978-3-319-07974-5_2
2. Yost, W. A. (2015). Psychoacoustics: A brief historical overview. Acoustics Today, 11(3), 46-53. https://acousticstoday.org/wp-content/uploads/2015/08/Psychoacoustics-A-Brief-Historical-Overview.pdf
3. Zhang, P. X. (2013). Psychoacoustics. In Handbook for sound engineers (pp. 62-83). Routledge. https://belglas.com/wp-content/uploads/2018/03/handbook-for-sound-engineers.pdf
4. Vican, I., Kreković, G., & Jambrošić, K. (2024). Improved fetal heartbeat detection using pitch shifting and psychoacoustics. Biomedical Signal Processing and Control, 90, 105850. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4181567
5. Schlesinger, J. (2016). Pulse oximetry: Perception, pitch, psychoacoustics, and pedagogy. Anesthesia & Analgesia, 122(5), 1253-1255.
6. Meeuws, M., Pascoal, D., Janssens de Varebeke, S., De Ceulaer, G., & Govaerts, P. J. (2020). Cochlear implant telemedicine: remote fitting based on psychoacoustic self-tests and artificial intelligence. Cochlear Implants International, 21(5), 260-268. https://pubmed.ncbi.nlm.nih.gov/32397922/
7. Maraci, M. A., Bridge, C. P., Napolitano, R., Papageorghiou, A., & Noble, J. A. (2017). A framework for analysis of linear ultrasound videos to detect fetal presentation and heartbeat. Medical image analysis, 37, 22-36. https://www.sciencedirect.com/science/article/pii/S1361841517300117
8. Chen, Y., Wilkins, M. D., Barahona, J., Rosenbaum, A. J., Daniele, M., & Lobaton, E. (2021, November). Toward automated analysis of fetal phonocardiograms: Comparing heartbeat detection from fetal doppler and digital stethoscope signals. In 2021 43rd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC) (pp. 975-979). IEEE. https://pubmed.ncbi.nlm.nih.gov/34891451/
9. Nitzan, M., Romem, A., & Koppel, R. (2014). Pulse oximetry: fundamentals and technology update. Medical Devices: Evidence and Research, 231-239. https://pubmed.ncbi.nlm.nih.gov/25031547/
10. Torp, K. D., Modi, P., & Simon, L. V. (2017). Pulse oximetry. StatPearls. NIH National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK470348/
11. Loeb, R. G., Brecknell, B., & Sanderson, P. M. (2016). The sounds of desaturation: a survey of commercial pulse oximeter sonifications. Anesthesia & Analgesia, 122(5), 1395-1403. https://pubmed.ncbi.nlm.nih.gov/27028772/
12. Sanderson, P. M., Loeb, R. G., Liley, H., Liu, D., Paterson, E., Hinckfuss, K., & Zestic, J. (2022). Signaling patient oxygen desaturation with enhanced pulse oximetry tones. Biomedical Instrumentation & Technology, 56(2), 46-57. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9767428/
13. Schwarz, S., & Ziemer, T. (2019, June). A psychoacoustic sound design for pulse oximetry. In 25th International Conference on Auditory Display (ICAD 2019) (pp. 23-27). https://repository.gatech.edu/server/api/core/bitstreams/811c2c1b-1dab-4acd-bf5b-7f73d11916f6/content
14. Burns, E. M. (1981). Circularity in relative pitch judgments for inharmonic complex tones: The Shepard demonstration revisited, again. Perception & Psychophysics, 30, 467-472. https://psycnet.apa.org/record/1982-22692-001
15. Deep, N. L., Dowling, E. M., Jethanamest, D., & Carlson, M. L. (2019). Cochlear implantation: an overview. Journal of Neurological Surgery Part B: Skull Base, 80(02), 169-177. https://pubmed.ncbi.nlm.nih.gov/30931225/
16. Pinero De Plaza, M. A., Beleigoli, A., Mudd, A., Tieu, M., McMillan, P., Lawless, M., Feo, R., Archibald, M.,  & Kitson, A. (2021). Not well enough to attend appointments: Telehealth versus health marginalisation. In Healthier Lives, Digitally Enabled (pp. 72-79). IOS Press. https://www.researchgate.net/publication/351040408_Not_Well_Enough_to_Attend_Appointments_Telehealth_Versus_Health_Marginalisation/fulltext/6080dd3b2fb9097c0cfde7f2/Not-Well-Enough-to-Attend-Appointments-Telehealth-Versus-Health-Marginalisation.pdf
17. DeHart, D., King, L. B., Iachini, A. L., Browne, T., & Reitmeier, M. (2022). Benefits and challenges of implementing telehealth in rural settings: A mixed-methods study of behavioral medicine providers. Health & Social Work, 47(1), 7-18. https://pubmed.ncbi.nlm.nih.gov/34910158/
18. Basile, C. É., Fournier, P., Hutchins, S., & Hébert, S. (2013). Psychoacoustic assessment to improve tinnitus diagnosis. PloS one, 8(12), e82995. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0082995
19. Enzler, F., Fournier, P., & Norena, A. J. (2021). A psychoacoustic test for diagnosing hyperacusis based on ratings of natural sounds. Hearing research, 400, 108124. https://pubmed.ncbi.nlm.nih.gov/33321385/
20. Ren, Z., Chang, Y., Bartl-Pokorny, K. D., Pokorny, F. B., & Schuller, B. W. (2022). The acoustic dissection of cough: diving into machine listening-based COVID-19 analysis and detection. Journal of Voice. https://www.sciencedirect.com/science/article/pii/S0892199722001667
21. Levine, R. A., & Oron, Y. (2015). Tinnitus. Handbook of clinical neurology, 129, 409-431. https://pubmed.ncbi.nlm.nih.gov/25726282/
22. Ziemer, T., Black, D., & Schultheis, H. (2017, June). Psychoacoustic sonification design for navigation in surgical interventions. In Proceedings of Meetings on Acoustics (Vol. 30, No. 1). AIP Publishing. https://pubs.aip.org/asa/poma/article/30/1/050005/908553/Psychoacoustic-sonification-design-for-navigation
23. Dimoulas, C., Kalliris, G., Papanikolaou, G., & Kalampakas, A. (2006). Novel wavelet domain Wiener filtering de-noising techniques: application to bowel sounds captured by means of abdominal surface vibrations. Biomedical signal processing and control, 1(3), 177-218. https://www.sciencedirect.com/science/article/abs/pii/S1746809406000322
24. Cyphers, N. A., Mest, C. G., & Doyle-Tadduni, M. E. (2019). Effect of psychoacoustic learning on cardiac auscultation proficiency in nurse practitioner students. Nurse Educator, 44(2), 79-83. https://pubmed.ncbi.nlm.nih.gov/30134440/

Further Reading

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• Insight into Implantable Medical Devices
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