Improved Sensitivity of Digits-in-Noise Test to High-Frequency Hearing Loss

Hearing loss is most commonly observed at high frequencies. High-frequency hearing loss (HFHL) precedes and predicts hearing loss at lower frequencies. It was previously shown that an automated, self-administered digits-in-noise (DIN) test can be sensitized for detection of HFHL by low-pass filtering the speech-shaped masking noise at 1.5 kHz. This study was designed to investigate whether sensitivity of the DIN to HFHL can be enhanced further using low-pass noise filters with higher cutoff frequencies.

The US-English digits 0 to 9, homogenized for audibility, were binaurally presented in different noise maskers including one broadband and three low-pass (cutoff at 2, 4, and 8 kHz) filtered speech-shaped noises. DIN-speech reception thresholds (SRTs) were obtained from 60 normal hearing (NH), and 40 mildly hearing impaired listeners with bilateral symmetric sensorineural hearing loss. Standard and extended high-frequency audiometric pure-tone averages (PTAs) were compared with the DIN-SRTs.

Narrower masking noise bandwidth generally produced better (more sensitive) mean DIN-SRTs. There were strong and significant correlations between SRT and PTA in the hearing impaired group. Lower frequency PTALF 0.5,1, 2, 4 kHz had the highest correlation and the steepest slope with SRTs obtained from the 2-kHz filter. Higher frequency PTAHF 4,8,10,12.5 kHz correlated best with SRTs obtained from 4- and 8-kHz filtered noise. The 4-kHz low-pass filter also had the highest sensitivity (92%) and equally highest (with the 8-kHz filter) specificity (90%) for detecting an average PTAHF of 20 dB or more.

Of the filters used, DIN sensitivity to higher frequency hearing loss was greatest using the 4-kHz low-pass filter. These results suggest that low-pass filtered noise may be usefully substituted for broadband noise to improve earlier detection of HFHL using DIN.