New Insights into Digital Noise Reduction
Digital noise reduction (DNR) has been shown to be beneficial for children and adults. Stelmachowicz et al (2010) evaluated 16 children (aged 5 to 10 years) with mild to moderately severe sensorineural hearing loss (SNHL) and reported "…no significant differences were observed across NR conditions for nonsense syllables, words, or sentences...." Specifically, noise reduction "on or off" was not a statistically significant variable with regard to the children's ability to correctly identify speech sounds in noise. Dillon (2012) stated modern hearing aid technology is so good that audiologists and dispensers should use noise reduction and directional microphones for children of all ages (just like adults), all the time.
Pittman (2011) evaluated word learning rates for children with normal hearing (n = 41) and children with hearing loss (n = 26) in quiet and noise, with respect to DNR. She reported younger children with hearing loss demonstrated significantly reduced word learning rates in noise and their speech perception was the same in quiet and in noise with and without DNR. However, for the older children, listening with DNR engaged was beneficial and DNR contributed significantly to word learning for the older children. Pittman (2013) notes some hearing aids employing an active DNR circuit can improve the signal-to-noise ratio (SNR) up to 6 dB.
Ng et al (2013) report an important deleterious effect of noise is impaired recall. Specifically, the researchers evaluated 26 experienced hearing aid wearers with moderate to moderately severe SNHL and they investigated background noise composed of competing speech as compared to speech-shaped noise and the impact on recall. Ng et al report listening in a background of speech noise is cognitively more demanding than listening in artificial noise because the lexical and semantic information available in speech is more distracting. Further, for people with high working memory capacity, noise reduction circuits were very useful and indeed, the DNR circuit "virtually canceled out" the disruptive effect of the competing speech with respect to recall. They conclude "noise reduction can reduce the adverse effect of noise on memory for speech...." for people with good working memory capacity...." and they report DNR allows speedier word identification and facilitates enhanced encoding of heard material into working memory.
For More Information, References, and Recommendations
Ng, EHN, Rudner M, Lunner T, Pedersen MS, Ronnberg J. (2013) Effects of Noise and Working Memory Capacity on Memory Processing of Speech for Hearing Aid Users. International Journal of Audiology 52:433-441.
Pittman A. (2011) Age-Related Benefits of Digital Noise Reduction for Short-Term Word Learning in Children With Hearing Loss. Journal of Speech, Language and Hearing Research 54 (October):1448-1463.