Comparison of amplification systems in a classroom.

"Listening systems" are used for hearing impaired listeners as an alternative to public address systems (PA) used for the general public. These listening systems allow individual control of sound pressure level and minimize the effects of background noise and room reverberation. Three listening systems, based on an audio induction loop (AL), frequency modulation of radio frequencies (FM), and modulation of infrared light (IR) were compared among themselves and with a PA system in a medium-size classroom. Listening groups were normal hearing, hearing impaired, hearing aid users, and elderly. Word identification scores were obtained with the Modified Rhyme Test at two conditions: with a babble of 12 voices at a speech-to-noise ratio (S/N) of + 8 dB, and without the babble at S/N of +20 dB. Analysis of variance indicated that the main effects of systems, groups and room S/N were significant. Also significant were interactions of systems by groups, and systems by S/N. For all groups, the three listening systems provided better scores than the PA system. It can be concluded that all three of the tested listening systems are suitable for listeners with various degrees of hearing losses.