Researching Speech Recognition

The following is a summary of sound enhancement efficacy studies demonstrating improvement in speech-recognition skills.

Study references and descriptions below taken from Sound Field Amplification: Applications to Speech Perception and Classroom Acoustics (Second Edition) by Carl C. Crandell, Joseph J. Smaldino, and Carol Flexer. This book is an invaluable resource for anyone researching this topic and highly recommended.

Updike & Conner (2003): Study included 495 first-grade students in regular education classes. Significant improvement in Goldman-Fristoe Test of Auditory Discrimination scores in quiet (76% to 92%) and noise (60% to 84%).

Mendel, Roberts, & Walton (2003): Study included 128 regular education kindergarten students with normal hearing. Two-year study showed significant and immediate improvement in speech perception and accelerated development of speech perception in noise by students in amplified classrooms.

Prendergast (2001): Study included 31 third-grade and 33 fourth-grade students with normal hearing. Enhanced performance was shown by all children on the California Consonant Test using the bending wave speaker vs. a traditional sound field speaker.

Lederman, Johnson, Crandell, & Smaldino (2000): Study included 72 third grade students (ELL, at risk, special education) and 9 third through fifth grade hard of hearing students. Significant improvement on 16 of 40 listening tasks (words and CV syllables) and conditions (S/N at -6, 0,+6dB) using the SmartSpeaker "Intelligence" digital signal processing sound field system with ambient noise compensation (ANC) capability.

Eriks-Brophy & Ayukawa (2000): Study included twenty second and third-grade students (10 with hearing loss and 10 age-matched peers). Significant improvements in speech intelligibility were noted for recognition of Inuttitut syllables by both groups of students when using a SES.

Gordon-Langbein & Metinger (1999): Study included two elementary classrooms. Students' abilities to identify initial consonant phonemes in words, using recorded questions, improved by 45% in the amplified conditions.

Allcock (1999): Study included three amplified and two unamplified elementary classrooms in New Zealand. After 8 weeks of sound field amplification use, students in amplified classrooms showed a 65-74% improvement of 1 stanine on the Test of Phonological Awareness compared to students in unamplified classes showing a 46% improvement of 1 stanine.

Crandell (1996): Study included 20 nonnative English speaking children. Improved speech-perception scores were achieved at distances of 12 and 24 feet when using a SES.

Zabel & Tabor (1993): Study included 145 regular education 3rd through 5th grade students. Students achieved improved spelling test scores under FM sound field amplification in quiet and under degraded listening at a +12 dB SNR.

Crandell (1993): Study included 20 students with normal hearing. Significantly higher word-recognition scores were achieved by students at distances of 12 and 24 feet when using a SES.

Flexer, Millin, & Brown (1990): Study included primary school-age children with developmental disabilities. Developmentally disabled students with history of persistent conductive hearing loss exhibited improved word-recognition scores.

Jones, Berg, & Viehweg (1989): Study included kindergarten students with normal hearing (N=18) and mild hearing loss (N=18). Use of FM sound field amplification decreased student-teacher distance and produced word-recognition scores comparable to close listening at 4 feet.

Blair, Myrup & Viehweg (1989): Study included ten students (CA=7-14 yrs) with mild to moderate SNHL. Students with mild to moderate SNHL demonstrated an average of 12% improvement in word-recognition score when using personal hearing aids with FM sound field over hearing aids alone.

Crandell & Bess (1986): Study included twenty students with normal hearing. Students showed significant improvement in sentence recognition ability under the amplified condition in typical classroom (S/N = +6 DB, RT=0.6 sec).