The Hearing in Noise Test (HINT) was developed at the House Ear Institute to measure speech recognition in quiet and in background noise to assess individual binaural directional hearing, which is critical in the understanding of speech in noise as well as in detecting and identifying sounds within an environment. These processing abilities are important to ensuring the safety of people with hearing-critical and potentially life-threating jobs such as those in law enforcement (police), fire protection, aviation, and armed services. The HINT has been successfully used for over a decade to determine the qualification of job applicants for these positions and predict when their hearing ability may diminish communication performance.
People who use hearing aids and apply for hearing-critical jobs are at a communication disadvantage as changes in the cochlea and auditory system affect both spectral and temporal processing, which in turn affect their ability to hear in background noise. Restoring audibility with hearing aids is only part of the equation as age-related changes or decreases in spatial processing can occur, especially with increased levels of hearing loss. For these reasons, most hearing aid users fail the HINT.
In this case study, the patient passed the aided HINT, but this may be because of several factors related to the patient's individual profile, in addition to having properly fitted and prescribed amplification. Clinicians should be aware of the factors that contribute to a patient's communication success or failure as well as his or her potential to pass the aided HINT and perform well with hearing aids.
Some individuals who pass the aided HINT may be given hearing-critical roles with some or no restrictions depending on the job requirements. If the Extended Speech Intelligibility Index (ESII) is applied across a job description, in addition to the Speech Intelligibility Index (SII) measures, other factors such as noise characteristics, distance, and vocal effort become part of the equation. Being able to see the job responsibilities as changing real-world events by measures within the soundscape allows for a more objective view of communication. For example, traffic officers at roadsides can be exposed to noise levels typically between 70 to 105 dBA, with passing trucks producing very loud low-frequency sounds that are considerably different from those encountered by corrections officers in controlled spaces like prison housing and dining areas (typically 65 to 80 dBA; Board of State and Community Corrections, 2013).
Passing the aided HINT does not guarantee that restrictions would not be encountered. An evaluation using the ESII would show that certain situations in both officers’ job descriptions could have less than a 50 percent chance of communication, even for those who are otologically normal. Recent research by Soli, et al., suggests that “ESII modeling of nonstationary real-world noise environments may prove an objective means of characterizing their impact on the likelihood of effective speech communication” (Ear Hear. 2018 May/Jun;39(3):436). This sets the standard for those in need of effective communication in critical-hearing jobs as well as the implementation of administrative controls. Combining this methodology with the HINT will help those seeking critical-hearing jobs and their prospective employers have a better understanding of the qualifications of the job and placement.
CONDUCTING THE HINT
HINT is an adaptive threshold test in which the subject is tasked with identifying and repeating short simple sentences (HINT 6.3 Manual). Scores are based on the reception thresholds for sentences (RTS), which is a 50 percent recognition score. Unlike the QuickSIN, testing under headphones simulates the head shadow, while sound field testing replicates the same test by placing two speakers at a 90-degree angle when testing the right or left ear. RTS scores are acquired with the test sentences presented from the front (0 degree azimuth). For tests in noise, in addition to speech from the front for the quiet test, noise is added to the front, right, or left side at a 90-degree angle. The quiet test is presented in dBA, while the noise tests are signal to noise ration scores in dB with 1 dB equivalent to approximately 10 percent of intelligibility.
Individuals with hearing impairment who wear hearing aids rarely can pass the aided HINT, and there is only anecdotal information to support the occurrences. These individuals fail because hearing loss affects temporal and spectral processing, which are critical in binaural directional hearing performance in noise.
Passing the HINT, whether it is performed using headphones or in a calibrated and normed sound field, is based on research on adults and children with normal hearing sensitivity (25 dB or better at 250 to 6,000 Hz). For most law enforcement jobs, the low fence is set at the fifth percentile of noise tests with a quiet RTS at or below 28 dBA.
CASE STUDY: BILATERAL MID- AND HIGH-FREQUENCY SENSORINEURAL HEARING LOSS
The patient is a 44-year-old man with an extensive history of noise exposure from working in the lumber industry. Additionally, the patient was exposed to firearms in the Navy, and occasionally used shotguns and handguns thereafter as a police officer. The patient has a family history of hearing loss, as both his brother and father wear hearing aids. The patient is an avid surfer and reported multiple episodes of external otitis and sinus infections over his lifetime. He denied having any medical conditions requiring medication, head/neck trauma, or barotrauma. He wants to return to police work after changing jobs for several years, but found that he needed to pass the HINT because of his hearing loss.
The patient has been wearing Widex Diva in-the-canal hearing aids with 2.0 mm vents for the past five years binaurally. The Abbreviated Profile of Hearing Aid Benefit (APHAB) revealed an excellent aided advantage with percent of problem scores for ease of communication (EC) of 6.5, reverberant room (RV) of 12.0, and background noise (BN) of 9.8. The only reversal of benefit from the unaided condition is averseness to unpleasant sound (AV) with a problem score of 83.
Using real ear probe microphones, the hearing aids were set to the NAL NL-1 prescription with minor changes made to improve audibility using sound field measurements as part of the verification process (Fig. 1). This included a reset of output and loud settings to reduce the averseness reported in the APHAB, which was confirmed by the patient when listening to various metal sound makers, kitchen pots and pans, crunching paper, and traffic noise.
The results of the unaided HINT and the aided HINT are presented in Table 1. Remarkably, the patient was able to pass the HINT in the clinic as well as at the House Ear Clinic. The factors that most likely contributed to the patient's success include his age, longevity of his hearing aid use, having a high-frequency hearing loss configuration (instead of flat), and having precisely prescribed and verified hearing aid setting and ear coupling. After passing the HINT, the patient was offered a position in the police department. The job offer noted some restrictions such as no patrol duty or crisis intervention, but he got a job he enjoyed.
Passing the HINT is difficult and nearly impossible for anyone with a hearing loss. Only two cases have been seen in this clinic in the past 10 years. When dealing with hearing-critical jobs, the use of the HINT, supported by an evaluation of the patient's possible real-world communication success, can be beneficial.