What the National Hearing Test Is

 

The National Hearing Test (NHT) is a telephone-administered screening test that presents three-digit sequences in a speech-spectrum noise background.  The speech-to-noise ratio (SNR) is adjusted using an adaptive procedure, to seek the threshold for 50% correct identification of the digit sequences.  A set of 25 sequences provides a reliable SNR threshold, in about four minutes of testing per ear.  Both right and left ears are tested.

 

The critical difference between the NHT and other telephone tests is that the NHT uses digits in noise, rather than pure tones.  Previous objections to telephone-administered tests were based on the unreliability of pure-tone tests administered over the telephone.  Because the NHT measures an SNR threshold, rather than one based on the absolute level of tones, the NHT can produce a reliable screening measure of hearing, despite the differences in sound levels produced by different telephones.

 

The NHT is made available as a screening to help decide whether to seek a full hearing evaluation.  In the promotion of the National Hearing Test, it is emphasized that the step after taking the test, for those whose performance is below the normal range, is to seek a full evaluation by an audiologist or doctor specializing in hearing.  Even those who pass the test are encouraged to have their hearing checked by an audiologist if they have concerns about their hearing.

 

 

The Development of Hearing Screening Tests with Spoken Digits in Noise

 

Scientists at VU University Medical Center in the Netherlands developed the first telephone hearing screenings based on spoken digits in noise.  The Dutch National Hearing Test was introduced in 2004 and has since served as a model for similar tests throughout Europe and in Australia.  The United Kingdom, Denmark, France, Germany, Poland, Switzerland, Spain, and Australia have developed and introduced their own versions of a telephone hearing screening, all using digit sequences presented in noise.  The growing popularity of this form of screening test is due in part to its demonstrated validity and reliability.  Testing by telephone is also a convenient, inexpensive way to determine whether a person’s functional hearing is within the normal range.

 

 

The Development of the National Hearing Test

 

The development of the U.S. version of a telephone screening began in 2008, when hearing scientists from Communication Disorders Technology, Inc., and Indiana University met with researchers from the Netherlands who developed the Dutch National Hearing Test.  By 2012 the U.S. version had been validated in two studies, one at the Indiana University Hearing Clinic and the other in collaboration with three hearing clinics administered by the VA.  The U.S. version has been found to be as reliable and valid a predictor of pure-tone losses as the telephone tests used in other countries.

 

 

Funding from NIH

 

The development of the National Hearing Test has been supported by research grants from the National Institute on Deafness and other Communication Disorders, a branch of the National Institutes of Health.  An article describing the NHT’s development and validation was recently published by the researchers who received the funding:

 

Watson, C. S., Kidd, G. R., Miller, J. D., Smits, C., & Humes, L. E.  (2012). Telephone screening tests for functionally impaired hearing: Current use in seven countries and development of a US version. Journal of the American Academy of Audiology, 23, 757-767. PubMed Abstract

 

 

The Scientists Who Developed the National Hearing Test

 

Dr. Charles S. Watson has been the principal investigator in the development of the U.S. version of the NHT.  He is a former chair of the Department of Speech and Hearing Sciences at Indiana University and a former Director of Research at the Boys Town National Research Hospital in Omaha.  He is now the President of Communication Disorders Technology, Inc., a company that has specialized in the development of hearing tests and speech perception training for hearing aid users since 1989.

 

Dr. Larry Humes is a Distinguished Professor in the Department of Speech and Hearing Sciences at Indiana University and is Chairman of that department.  He is an internationally recognized authority in auditory perception, with special expertise in the effects of hearing impairment and aging on auditory perception.  His most recent research activities have focused on age-related changes in speech perception and the evaluation of treatments for speech-perception deficits, including hearing aids and auditory training.

 

Dr. Gary Kidd is an Associate Scientist in the Department of Speech and Hearing Sciences at Indiana University and a Senior Scientist at Communication Disorders Technology, Inc.  He is the author of numerous articles on the perception of complex sounds, both speech and nonspeech, and on individual differences in auditory abilities.

 

Dr. James Miller is the Emeritus Director of Research at the Central Institute for the Deaf in St. Louis.  He is also an Adjunct Professor in the Department of Speech and Hearing Sciences at Indiana University.  He serves as Principal Scientist at Communication Disorders Technology, Inc., where he is conducting a series of studies on the effectiveness of speech perception training for hearing aid users and for ESL students.

 

Dr. Cas Smits is a Biophysicist/Audiologist in the Dept. of Otolaryngology/Audiology at VU University Medical Center in Amsterdam, the Netherlands.  He is the Chairman of the assembly of Dutch Cochlear Implant teams.  He was the original developer of the digits-in-noise test that was first used in the Netherlands and subsequently copied in several European countries and Australia.  His publications include:

 

Smits, C., & Houtgast, T. (2005). Results from the Dutch speed-in-noise screening test by telephone. Ear & Hearing, 26, 89-95. PubMed Abstract

 

Smits, C., Kapteyn, T. S., & Houtgast, T. (2004). Development and validation of an automatic speech-in-noise screening test by telephone. International Journal of Audiology, 43, 1-15. PubMed Abstract

 

 

The NHT Clinical Advisory Committee

 

The following scientists and audiologists have been important in the development of the NHT, through their advice and counsel on such topics as the need for clarity regarding the difference between screening and diagnostic tests, and the claims that can properly be made about the validity of telephone testing.

 

Judy R. Dubno, Ph.D., CCC-A, Medical University of South Carolina

Larry E. Humes, Ph.D., FAAA, Indiana University

Nancy Nelson, Aud.D., CCC-A, Indiana University

Jill Preminger, Ph.D., CCC-A, University of Louisville

David Wark, Ph.D., CCC-A, University of Memphis

Gail Whitelaw, Ph.D., CCC-A, Ohio State University

 

 

The National Hearing Test and Hearing Professionals

 

The NHT is presented as a screening test with the goal of encouraging those who fail the test to seek a complete audiological evaluation.  The results of the NHT are given for each ear in the following terms:  Normal, Slightly Below Normal, and Poor.  Those whose results are not in the Normal category are advised to seek an evaluation of their hearing by an audiologist or a doctor specializing in hearing.  At the end of the telephone screening, test takers receive their results while they are still on the phone.

 

NIH has provided funding to promote the NHT to the public and for follow-up research to determine whether persons who fail the screening test comply with recommendations to seek full hearing evaluations.

 

The NHT website provides links to the websites of the American Academy of Audiology and the American Speech-Language-Hearing Association.  Each of these sites has a directory for finding certified audiologists in specific areas of the country.  Note that the NHT does not endorse any individual service provider who may be identified in this way.  We do recommend that full hearing assessments be made by certified or licensed audiologists. The NHT has no financial association with service providers.  Names and addresses of those who take the test and their test results are kept strictly private and are not shared with any person or organization.

 

 

Contact Us for More Information

 

If you are a hearing professional with a question about the NHT, please send your questions to:   research@nationalhearingtest.org