New Technologies and Applications using the Speech-evoked Frequency Following Response

听力障碍在加拿大是一个重要的健康问题，有必要开发改进的技术来客观地评估听力。当声音到达耳朵时，小的电脉冲通过大脑的听觉中心传播，最终产生听觉的感觉。关于这个过程，我们还没有很好地理解，但是通过在头皮上放置表面电极，我们可以无创地记录来自这些听觉中心的电活动。特别是，记录听觉脑干反应是可能的，这使听力学家能够诊断听力问题并确定其在大脑中的起源。听力学家在这个测试中最常用的声音是一个简短的响亮的咔哒声。然而，点击并不能提供足够的信息来评估听语音的能力。因此，人们对记录随时间和频率模式的大脑电反应越来越感兴趣。最近，我们的研究小组记录了自然和合成语音刺激下的语音诱发频率跟随反应（speech - induced Frequency Following Responses, sFFRs），并表明这些反应可以为语音的听觉处理提供一个重要的窗口。sFFR与语音波形非常相似，如果它被转换成声音并播放，它被认为是可理解的语音。这意味着这个信号允许我们“监听”大脑内部的语音表达。

Hearing impairment is an important health problem in Canada, and there is a need to develop improved technologies to objectively evaluate hearing. When sound reaches the ear, small electrical pulses propagate through the auditory centers in the brain, eventually resulting in the sensation of hearing. Much about this process is not well-understood, but by placing surface electrodes on the scalp we can non-invasively record the electrical activity originating in these auditory centers. In particular, it is possible to record auditory brainstem responses, which allow audiologists to diagnose hearing problems and locate their origin in the brain. The sound that audiologists most commonly use for this test is a brief loud click. However, a click does not provide sufficient information to allow assessing the ability to hear speech. As a result, there is increasing interest in recording the brain's electrical responses that follow the temporal and frequency patterns of speech. Recently, our group has recorded Speech-evoked Frequency Following Responses (sFFRs) with natural and synthetic speech stimuli, and we have shown that these responses can provide an important window into auditory processing of speech. The sFFR is so similar to the speech waveform, that if it is converted to a sound and played back, it is perceived as intelligible speech. This means that this signal allows us to "listen in" on the internal representation of speech within the brain. One impediment to progress in this field has been that excessive recording times are often required. The proposed research program aims to develop more efficient techniques to detect the sFFR that are inspired by speech enhancement algorithms developed for noisy communication environments. Moreover, because the sFFR has been recorded in response to a limited set of speech stimuli, experimental and theoretical work will be performed with listeners who have normal hearing to clarify the basic properties of the responses, with a diverse set of speech samples and in different realistic acoustic environments. A new brain-computer interface technology based on the sFFR will also be developed to automatically optimize hearing aid fitting, which is often a challenging task. The proposed research program is expected to have a significant impact in the field of Biomedical Engineering and on hearing assistive technologies. Novel techniques for the assessment of hearing function will be developed, including new signal processing algorithms and instrumentation for detecting speech-evoked responses, improved models of human auditory processing of speech, and new technologies for objective hearing aid fitting. Moreover, Doctoral and Master's students will be trained in interdisciplinary and collaborative research, and so will develop skills of value to the Canadian biomedical and hearing devices industries, the hearing and speech research communities, and healthcare.