Division of Signal Processing and Biomedical Engineering, Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
Division of Ear, Nose and Throat Diseases, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden.
Ear Hear. 2020 Mar/Apr;41(2):411-419. doi: 10.1097/AUD.0000000000000764.
Unilateral hearing loss (UHL) is a condition as common as bilateral hearing loss in adults. Because of the unilaterally reduced audibility associated with UHL, binaural processing of sounds may be disrupted. As a consequence, daily tasks such as listening to speech in a background of spatially distinct competing sounds may be challenging. A growing body of subjective and objective data suggests that spatial hearing is negatively affected by UHL. However, the type and degree of UHL vary considerably in previous studies. The aim here was to determine the effect of a profound sensorineural UHL, and of a simulated UHL, on recognition of speech in competing speech, and the binaural and monaural contributions to spatial release from masking, in a demanding multisource listening environment.
Nine subjects (25 to 61 years) with profound sensorineural UHL [mean pure-tone average (PTA) across 0.5, 1, 2, and 4 kHz = 105 dB HL] and normal contralateral hearing (mean PTA = 7.2 dB HL) were included based on the criterion that the target and competing speech were inaudible in the ear with hearing loss. Thirteen subjects with normal hearing (19 to 60 years; mean left PTA = 4.1 dB HL; mean right PTA = 5.5 dB HL) contributed data in normal and simulated "mild-to-moderate" UHL conditions (PTA = 38.6 dB HL). The main outcome measure was the threshold for 40% correct speech recognition in colocated (0°) and spatially and symmetrically separated (±30° and ±150°) competing speech conditions. Spatial release from masking was quantified as the threshold difference between colocated and separated conditions.
Thresholds in profound UHL were higher (worse) than normal hearing in separated and colocated conditions, and comparable to simulated UHL. Monaural spatial release from masking, that is, the spatial release achieved by subjects with profound UHL, was significantly different from zero and 49% of the magnitude of the spatial release from masking achieved by subjects with normal hearing. There were subjects with profound UHL who showed negative spatial release, whereas subjects with normal hearing consistently showed positive spatial release from masking in the normal condition. The simulated UHL had a larger effect on the speech recognition threshold for separated than for colocated conditions, resulting in decreased spatial release from masking. The difference in spatial release between normal-hearing and simulated UHL conditions increased with age.
The results demonstrate that while recognition of speech in colocated and separated competing speech is impaired for profound sensorineural UHL, spatial release from masking may be possible when competing speech is symmetrically distributed around the listener. A "mild-to-moderate" simulated UHL decreases spatial release from masking compared with normal-hearing conditions and interacts with age, indicating that small amounts of residual hearing in the UHL ear may be more beneficial for separated than for colocated interferer conditions for young listeners.
单侧听力损失（UHL）在成年人中与双侧听力损失一样常见。由于 UHL 导致单侧可听度降低，因此声音的双耳处理可能会受到干扰。因此，在背景中存在空间上不同的竞争声音的情况下聆听言语等日常任务可能具有挑战性。越来越多的主观和客观数据表明，UHL 会对空间听觉产生负面影响。然而，以前的研究中 UHL 的类型和程度差异很大。本研究的目的是确定深度感音神经性 UHL 和模拟 UHL 对竞争语音识别的影响，以及在要求较高的多源听力环境中双耳和单耳对掩蔽释放的贡献。
根据目标和竞争语音在听力损失耳中听不见的标准，纳入了 9 名（25 至 61 岁）深度感音神经性 UHL 患者[0.5、1、2 和 4 kHz 处的纯音平均听阈（PTA）平均值= 105 dB HL]和正常对侧听力（平均 PTA = 7.2 dB HL）。13 名听力正常的受试者（19 至 60 岁；左 PTA 平均值= 4.1 dB HL；右 PTA 平均值= 5.5 dB HL）在正常和模拟“轻度至中度”UHL 条件下（PTA = 38.6 dB HL）提供了数据。主要观察指标为在共定位（0°）和空间和对称分离（±30°和±150°）竞争语音条件下 40%正确语音识别的阈值。掩蔽释放的空间量度为共定位和分离条件之间的阈值差异。
与正常听力相比，深度 UHL 的阈值在分离和共定位条件下更高（更差），与模拟 UHL 相当。单耳掩蔽释放，即深度 UHL 患者实现的空间释放，与零显著不同，并且与正常听力患者实现的空间掩蔽释放的幅度相差 49%。一些深度 UHL 患者表现出负空间释放，而正常听力患者在正常条件下始终表现出掩蔽释放的正空间释放。模拟 UHL 对分离条件下的语音识别阈值的影响大于共定位条件，导致掩蔽释放减少。正常听力和模拟 UHL 条件之间的空间释放差异随年龄增长而增加。
结果表明，虽然在共定位和分离的竞争语音中识别言语受到深度感音神经性 UHL 的损害，但当竞争语音对称分布在听众周围时，可能会实现掩蔽释放。与正常听力条件相比，“轻度至中度”模拟 UHL 降低了掩蔽释放，并且与年龄相互作用，这表明 UHL 耳中的少量残余听力对年轻听众的分离干扰条件比对共定位干扰条件更有益。
