Frequency Lowering for Patients with Mild-to-Moderate SNHL?
Alexander, Kopun, and Stelmachowicz (2014) report their results with regard to two frequency lowering protocols: (1) frequency transposition (FT) via the Widex Inteo (source region spanned 4.2 to 7 kHz, target region spanned 2.1 to 3.5 kHz) and (2) non-linear frequency compression (NFC) via the Phonak Naida (source region was spanned 4 to 6 kHz and target region was 4 to 4.7 k Hz). The authors also evaluated a novel algorithm (spectral envelope decimation, SED) and a wide-band (WB) simulation across adults with 24 normal hearing and 24 adults with mild-to-moderate hearing loss. Their goal was to test the efficacy of frequency lowering technologies for adults with mild-to-moderate sensorineural hearing loss (SNHL. Of note, NFC and FT were not designed for this patient population).
The authors note that the relationship between the degree of hearing loss and the amount of frequency lowering appears to be “give and take.” That is, “While there is more speech information to be gained from frequency lowering” as hearing loss increases, the target bandwidth into which the lowered information is to be delivered “becomes increasingly narrow.”
Alexander, Kopun, and Stelmachowicz report that “for normal hearing and hearing impaired listeners, performance with FT was significantly worse compared with that in the other conditions.” And they report that “consistent with previous findings, performance for the hearing impaired listeners in the WB condition was significantly better than in the FT-Off condition.” The authors note that SED and WB conditions were significantly better than NFC (with 6kHz input bandwidth) and NFC-Off and there were no differences in performance between SED and WB, indicating fricative identification may be improved via WB and through the SED novel frequency-lowering algorithm. They state that there exists a potential benefit from SED or NFC in this population of patients (mild-to-moderate SNHL) and they caution against using FT for this same group.
For More Information, References, and Recommendations
Alexander JM, Kopun JG, Stelmachowicz PG. (2014) Effects of Frequency Compression and Frequency Transposition on Fricative and Africate Perception in Listeners with Normal Hearing and Mild to Moderate Hearing Loss. Ear & Hearing 35(5):519-532.