Pittman A L, Lewis D E, Hoover B M, Stelmachowicz P G
Boys Town National Research Hospital, Omaha, Nebraska 68131, USA.
Ear Hear. 1999 Aug;20(4):279-89. doi: 10.1097/00003446-199908000-00001.
Children with moderate to severe hearing loss routinely use personal frequency modulated (FM) systems in the classroom to improve the signal to noise ratio of teacher-directed speech with notable success. Attention is now being given to the ability of these children to hear other students via the hearing aid (HA) microphone while using an FM system. As a result, a variety of FM system and HA microphone combinations have been recommended for classroom use. To date, there are no studies regarding the efficacy of these FM/HA combinations. The purpose of this study was to evaluate recognition performance using four FM/HA combinations and to characterize that performance for stimuli received primarily through FM system and HA microphone transmission.
Recognition performance for FM system and HA microphone signals was evaluated for two symmetrical and two asymmetrical FM/HA combinations using two commercially available FM systems (one conventional and one FM-precedence circuit). Eleven children (ages 9 to 12) with moderate to severe sensorineural hearing loss and eight children (ages 10 to 11) with normal hearing served as subjects. The two symmetrical FM/HA combinations included: 1) binaural FM system and HA microphone input using the conventional FM system, and 2) binaural FM and HA input using the FM-precedence circuit. The conventional FM system was used for the two asymmetrical combinations and included: 1) binaural FM input and monaural HA input, and 2) FM input to one ear and HA input to the other. Stimuli were 33 consonants presented in the form of nonsense syllables. The stimuli were presented through three loudspeakers representing a teacher and two fellow students in a classroom environment. Speech shaped noise was presented through two additional loudspeakers.
In general, no statistically significant differences in recognition performance were found between any of the FM/HA combinations. Mean recognition scores for HA microphone transmission (55%) were significantly poorer than those for FM system transmission (75%). As expected, initial consonants were more easily recognized than final consonants via FM system and HA microphone transmission. However, voiceless consonants were more easily recognized than voiced consonants via HA microphone transmission, which was not predicted on the basis of previous research.
These results suggest that a certain amount of flexibility is present when choosing an FM/HA combination. However, recognition performance via the HA microphones was consistently poorer than performance via FM transmission. Because relevant material also originates from fellow students (e.g., answering teacher-directed questions), input via the HAs is often as important as information originating from the teacher. The results suggest that attempts to improve performance for signals transmitted through the HA microphones in a classroom setting would benefit children with hearing loss.
中重度听力损失儿童通常在课堂上使用个人调频（FM）系统，以提高教师授课语音的信噪比，效果显著。目前人们开始关注这些儿童在使用FM系统时通过助听器（HA）麦克风聆听其他学生讲话的能力。因此，已推荐了多种用于课堂的FM系统和HA麦克风组合。迄今为止，尚无关于这些FM/HA组合功效的研究。本研究的目的是评估四种FM/HA组合的识别性能，并描述主要通过FM系统和HA麦克风传输所接收刺激的该性能特征。
使用两种市售FM系统（一种传统系统和一种FM优先电路）评估了两种对称和两种不对称FM/HA组合的FM系统和HA麦克风信号的识别性能。11名中重度感音神经性听力损失儿童（9至12岁）和8名听力正常儿童（10至11岁）作为受试者。两种对称的FM/HA组合包括：1）使用传统FM系统的双耳FM系统和HA麦克风输入，以及2）使用FM优先电路的双耳FM和HA输入。传统FM系统用于两种不对称组合，包括：1）双耳FM输入和单耳HA输入，以及2）一只耳朵的FM输入和另一只耳朵的HA输入。刺激为以无意义音节形式呈现的33个辅音。刺激通过代表教师和教室里两名同学的三个扬声器呈现。言语噪声通过另外两个扬声器呈现。
总体而言，任何FM/HA组合之间在识别性能上均未发现统计学上的显著差异。HA麦克风传输的平均识别分数（55%）明显低于FM系统传输的平均识别分数（75%）。正如预期的那样，通过FM系统和HA麦克风传输，起始辅音比结尾辅音更容易识别。然而，通过HA麦克风传输，清辅音比浊辅音更容易识别，这与先前的研究预测不符。
这些结果表明，在选择FM/HA组合时有一定的灵活性。然而，通过HA麦克风的识别性能始终低于通过FM传输的性能。由于相关内容也来自其他同学（例如，回答教师的提问），通过HA的输入通常与来自教师的信息一样重要。结果表明，在课堂环境中提高通过HA麦克风传输信号的性能的尝试将使听力损失儿童受益。
