“Normal” hearing at any frequency in humans is defined as the ability to perceive a sound at a
volume of 20 dB or less. Hearing loss is not considered to be “severe” until the volume required
to perceive a sound reaches a threshold of 70 dB, and “profound” hearing loss (or deafness)
occurs when the sound must be 100 dB or more in volume to be heard. Given these ranges of
hearing and the corresponding degrees of hearing loss, it is reasonable to ask if a 10 dB hearing
loss is actually significant. For example, if a person with normal hearing at baseline is exposed
to a stimulus that is harmful to the ears (such as loud music or an ototoxic substance) and that
person’s hearing is 10 dB worse as a result, does this matter, considering that he or she is still
far from being deaf?
There is good reason to conclude that a 10 dB hearing loss is indeed significant. Because the
decibel scale is logarithmic, a 10 dB reduction in hearing means that a sound would need to be
10-times more intense to evoke the same perception as before the hearing loss. This would
likely make a significant difference in an individual’s ability to accurately perceive the clarity of
speech that he or she is hearing, especially in a noisy environment (Campbell et al., 2016).
The conclusion that a 10 dB hearing loss is clinically relevant is supported by workplace
standards set by the Occupational Safety and Health Administration (OSHA). According to these
standards, if a worker sustains a 10 dB reduction in hearing at three frequencies and has at
least a mild hearing loss as a result of occupational noise exposure, a significant work related
injury (WRI) has occurred. Such a WRI must be reported, and is used to monitor hazardous
work areas. The Department of Defense has adopted an identical standard for defense-related
work environments (Campbell et al., 2016).
Because a 10 dB hearing loss is significant, it can be concluded that a 10 dB improvement in
hearing is clinically meaningful as well. This should be encouraging to developers of treatments
for hearing improvement. Sponsors of preclinical and clinical efficacy trials of otic treatments
might assume that a 10 dB improvement relative to controls is too small to matter, and that
only improvements of 20 dB or more are promising. In reality, a 10 dB improvement in hearing
could generate great enthusiasm among clinicians, scientists, and investors. A trial at St. Jude
Children’s Research Hospital in Tennessee serves as an example. A team of scientists screened
more than 4,000 small molecules as protectors against cisplatin-induced hearing loss, and the
most successful molecule (kenpaullone, a CDK2 inhibitor) minimized hearing loss by 10 dB (Teitz
et al., 2018). Significant excitement was generated, including an article in MedicalNewsToday
announcing that a “new drug ‘could save the hearing of millions’” (Railton, 2018).
Campbell, K., Hammill, T., Hoffer, M., Kil, J., & Le Prell, C. (2016). Guidelines for auditory
threshold measurement for significant threshold shift. Otol Neurotol 37, e263-e270.
Railton, D. (2018). New drug ‘could save the hearing of millions’, in MedicalNewsToday
Teitz T., Fang, J., Goktug, A.N., Bonga, J.D., Diao, S., Hazlitt, R.A., et al. (2018). CDK2 inhibitors as
candidate therapeutics for cisplatin- and noise-induced hearing loss. J Exp Med 215(4), 1187-
David Hicks, M.D.: Dr. Hicks directs business development at Turner Scientific, and has
significant training and experience in clinical treatment of ear disorders. Contact:
Jeremy Turner, Ph.D.: Dr. Turner is the founder and Chief Scientific Officer at Turner Scientific.
He completed his Ph.D. in auditory neuroscience, and has more than 22 years’ experience in
preclinical hearing loss, tinnitus, and ototoxicity research. Contact: firstname.lastname@example.org