Effects of Frequency Compression and Frequency Transposition on Fricative and Affricate Perception in Listeners With Normal Hearing and Mild to Moderate Hearing Loss

Abstract

Summary: Listeners with normal hearing and mild to moderate loss identified fricatives and affricates that were recorded through hearing aids with frequency transposition (FT) or nonlinear frequency compression (NFC). FT significantly degraded performance for both groups. When frequencies up to ~9 kHz were lowered with NFC and with a novel frequency compression algorithm, spectral envelope decimation, performance significantly improved relative to conventional amplification (NFC-off) and was equivalent to wideband speech. Significant differences between most conditions could be largely attributed to an increase or decrease in confusions for /s/ and /z/. Objectives: Stelmachowicz and colleagues have demonstrated that the limited bandwidth associated with conventional hearing aid amplification prevents useful high-frequency speech information from being transmitted. The purpose of this study was to examine the efficacy of two popular frequency-lowering algorithms and one novel algorithm (spectral envelope decimation) in adults with mild-to-moderate sensorineural hearing loss and in normal-hearing controls. Design: Participants listened monaurally through headphones to recordings of nine fricatives and affricates spoken by three women in a vowel-consonant (VC) context. Stimuli were mixed with speech-shaped noise at 10 dB SNR and recorded through a Widex Inteo IN-9 and a Phonak Naída UP V behind-the-ear (BTE) hearing aid. Frequency transposition (FT) is used in the Inteo and nonlinear frequency compression (NFC) used in the Naída. Both devices were programmed to lower frequencies above 4 kHz, but neither device could lower frequencies above 6-7 kHz. Each device was tested under four conditions: frequency lowering deactivated (FT-off and NFC-off), frequency lowering activated (FT and NFC), wideband (WB), and a fourth condition unique to each hearing aid. The WB condition was constructed by mixing recordings from the first condition with high-pass filtered versions of the source stimuli. For the Inteo, the fourth condition consisted of recordings made with the same settings as the first, but with the noise reduction feature activated (FT-off). For the Naída, the fourth condition was the same as the first condition except that source stimuli were pre-processed by a novel frequency compression algorithm, spectral envelope decimation (SED), designed in MATLAB that allowed for a more complete lowering of the 4-10 kHz input band. A follow up experiment with NFC used Phonak’s Naída SP V BTE, which could also lower a greater range of input frequencies. Results: For normal-hearing (NH) and hearing-impaired (HI) listeners, performance with FT was significantly worse compared to the other conditions. Consistent with previous findings, performance for the HI listeners in the WB condition was significantly better than in the FT-off condition. In addition, performance in the SED and WB conditions were both significantly better than the NFC-off condition and the NFC condition with 6 kHz input bandwidth. There were no signifi...

The effects of frequency lowering on speech perception in noise with adult hearing-aid users

“…The majority of studies have used high frequency weighted stimuli with little contextual information, such as phoneme or plural recognition (Alexander et al, 2014; Auriemmo et al, 2009; Glista et al, 2009; Glista et al, 2012; Simpson et al, 2005; Wolfe et al, 2010). Phonemes with high frequency energy, such as affricates and fricatives, can contain frequencies beyond the bandwidth of conventional processing and therefore may potentially be more audible with FL.…”

“…Audibility of high frequency cues is even more important in background noise, where a wider bandwidth is required to equate performance to that obtained in quiet (Silberer et al, 2015). For more information on the contribution of high frequency information to speech perception, see the introduction of Alexander et al (2014).…”

“…This information would be useful for clinicians when selecting a frequency lowering technology for a patient. Alexander et al (2014) compared NFC and LFT using high-frequency loaded fricatives and affricates in speech-shaped noised at 10 dB SNR in listeners with hearing loss. Fricative and affricate identification was poorer with LFT activated compared to deactivated, while identification was the same with NFC activated compared to deactivated.…”

Listening Effort and Speech Recognition with Frequency Compression Amplification for Children and Adults with Hearing Loss

“…Findings are mixed on the effect of NFC relative to RBW on speech recognition and potential relationships are complex (Alexander, 2013; Alexander et al, 2014; Arehart et al, 2013; Bentler et al, 2014; Ching et al, 2013; Ellis & Munro, 2015; Glista et al, 2009; Glista et al, 2012; Hopkins et al, 2014; John et al, 2014; Kokx-Ryan et al, 2015; McCreery et al, 2013, 2014; Picou et al, 2015; Simpson et al, 2005, 2006; Souza et al, 2013; Wolfe et al, 2010, 2011, 2015). In general, benefit from NFC is better when access to high frequency sounds is increased with NFC (McCreery et al, 2013, 2014) but spectral distortion is minimized (Souza et al, 2013) as well as in listeners with greater high-frequency hearing loss (Brennan et al, 2014; Glista et al, 2009; Souza et al, 2013; but see Kokx-Ryan et al, 2015).…”

Effectiveness of Frequency-Lowering Hearing Aids and Electric Acoustic Stimulation Cochlear Implant for Treating People with a Severe-To-Profound High-Frequency Hearing Loss

“…This suggests that there is a potential risk to degrade the patient's hearing abilities with the use of FL, even if the person reports a better benefit in real-life with this technology, as it was the case for three participants during this study (S3, S9 and S12). This risk may be greater with LFT HAs, as reported in previously published studies [41,42]. Then, FL HAs may not be suitable for all patients with a HFHL, particularly those with a more severe hearing loss in mid frequencies.…”