Department of Communicative Disorders and Allied Health, Northern Illinois University, DeKalb, IL 60115, USA.
Ear Hear. 2013 Jul-Aug;34(4):470-81. doi: 10.1097/AUD.0b013e31827aaa95.
Wind noise can be a nuisance to hearing aid users. With the advent of sophisticated feedback reduction algorithms, people with higher degrees of hearing loss are fit with larger vents than previously allowed, and more people with lesser degrees of hearing loss are fit with open hearing aids. The purpose of this study was to examine the effects of venting on wind noise levels in the ear canal for hearing aids with omnidirectional and directional microphones.
Two behind-the-ear hearing aids were programmed when they were worn on a Knowles Electronics Manikin for Acoustic Research. The hearing aid worn on the right ear was programmed to the omnidirectional microphone mode and the one on the left to the directional microphone mode. The hearing aids were adjusted to linear amplification with flat frequency response in an anechoic chamber. Gains below 10 dB were used to avoid output limiting of wind noise levels at low input levels. Wind noise samples were recorded at the eardrum location in a wind tunnel at wind velocities ranging from a gentle to a strong breeze. The hearing aids were coupled to #13 tubings (i.e., open vent), or conventional skeleton earmolds with no vent, pressure vents, or 3mm vents. Polar and spectral characteristics of wind noise were analyzed off-line using MatLab programs.
Wind noise levels in the ear canals were mostly predicted by vent-induced frequency response changes in the conventional earmold conditions for both omnidirectional and directional hearing aids. The open vent condition, however, yielded the lowest levels, which could not be entirely predicted by the frequency response changes of the hearing aids. This indicated that a wind-related vent effect permitted an additional amount of sound reduction in the ear canal, which could not be explained by known vent effects.
For the microphone location, form factor, and gain settings tested, open fit hearing aids yielded lower noise levels at the eardrum location than conventional behind-the-ear hearing aids.
风声可能会给助听器使用者带来困扰。随着复杂的反馈抑制算法的出现，听力损失程度较高的人可以使用比以前允许的更大的通气孔来适配助听器，而听力损失程度较低的人也可以使用开放式助听器。本研究的目的是检查在具有全向和指向性麦克风的助听器中，通气孔对耳道中风噪声水平的影响。
在 Knowles Electronics Manikin for Acoustic Research 上佩戴两个耳背式助听器进行编程。右耳佩戴的助听器编程为全向麦克风模式，左耳佩戴的助听器编程为指向性麦克风模式。在消声室内，助听器调整为线性放大，频率响应平坦。增益低于 10dB 以避免在低输入水平下风噪声水平的输出限制。在风速从微风到强风的风洞中，在鼓膜位置记录风噪声样本。助听器与 #13 管（即开放式通气孔）或无通气孔、压力通气孔或 3mm 通气孔的传统骨架耳模耦合。使用 MatLab 程序在线下分析风噪声的极坐标和频谱特性。
在全向和指向性助听器的传统耳模条件下，风噪声水平主要由通气孔引起的频率响应变化来预测。然而，开放式通气孔条件产生的噪声水平最低，这不能完全由助听器的频率响应变化来预测。这表明与风有关的通气孔效应允许在耳道中额外减少声音，这不能用已知的通气孔效应来解释。
在测试的麦克风位置、外形因素和增益设置下，开放式适配助听器在鼓膜位置产生的噪声水平低于传统耳背式助听器。
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