Doctoral Dissertation Research: Lexical Acoustics

这个项目将通过观察英语听者在嘈杂环境中对单词的正确识别和单词之间的混淆模式，记录英语听者用于交流的语音信号的声学特性。该项目将加强对语音产生和感知的理解，特别是关于声音特征如何在语言单词中分布，以尽量减少误解，从而促进可靠的交流。更广泛地说，这项工作与研究成人和儿童的语音和单词知识之间的关系有关，有助于识别影响第二语言学习者的语言之间的独特差异，并最终为关注日常交流中各种类型的听力障碍的模型提供信息。对比了语言语音系统结构的两种一般模式。第一个模型，被称为“清单模型”，是一种规范的方法，它构成了语音感知中大多数语音系统描述的基础。在清单模型下，声音系统被构造为一组固定的对比辅音和元音，这组辅音和元音在权重上被视为均匀的，这样所有元素在定义系统和确定单个声音线索的相对重要性方面都起着平等的作用。第二个模型被称为词典模型，它认为对比音系统在词典中是严格分布的，因此不同线索的相对权重现在取决于这些线索用来区分的单词的数量和配置。在对比这两种方法时，提出了两个主要问题：(1)模型在线索权重估计方面的一致性有多好，以及一致性和不一致性的原因是什么；(2)在环境中存在背景噪声时，每个模型对系统稳定性的影响。清单模型使用一个控制音节产生的数据库来预测先前发表的声音之间的混淆模式，然后用线索权重来衡量模型中预测听众感知模式的每个线索的相对重要性。对于词典模型，使用一个由单个说话者产生的近27,000个单词的数据库来预测听者的单词识别模式，当这些单词被嵌入在一系列六个实验中的噪声中，使用不同的任务（开放、填空识别和两个发音相近的单词之间的封闭选择）和不同的刺激（自然产生、增强和减弱）。然后比较这两个模型拟合的线索权重来解决第一个问题。为了回答第二个问题，在不同的线索中加入噪声的模拟，以及由此导致的声音（在库存情况下）和单词（在词典情况下）之间预测相似性的变化，用于研究每个系统对声学信号不确定性的稳定性和自适应响应。因此，这些实验将能够解决语言中声音系统的结构和组织的关键主张。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will document which acoustic properties of the speech signal English listeners use to communicate by looking at patterns in both their correct recognition of words, and their confusions between words, when listening in a noisy environment. The project will enhance understanding of speech production and perception, particularly regarding how acoustic features are distributed throughout the words of a language to minimize misperceptions and therefore facilitate reliable communication. More broadly, this work is relevant for research on the relation between speech sounds and word knowledge in both adults and children, contributing to the identification of unique distinctions between languages that affect second language learners, and ultimately informing models focusing on various types of hearing impairment in everyday communication.Two general models of the structure of the sound system of a language are contrasted. The first model, referred to as the "inventory model", is the canonical approach that forms the basis for most phonetic descriptions of sound systems in speech perception. Under the inventory model, the sound system is structured as a fixed set of contrastive consonants and vowels, where this set is treated as homogeneous in weight such that all elements play an equal role in defining the system and determining the relative importance of individual acoustic cues. The second model, referred to as the lexicon model, considers the system of contrastive sounds to be critically distributed over the lexicon, such that the relative weight of different cues now depends on the number and configuration of words those cues serve to distinguish. In contrasting these two approaches, two main questions are asked: (1) how well do the models agree in their estimates of cue weights, and what accounts for points of agreement and disagreement; and (2) what does each model entail for the stability of the system in the presence of background noise in the environment. The inventory model uses a database of controlled productions of syllables to predict prior-published confusion patterns between sounds, with cue weights then measured as the relative importance of each cue in the model predicting listener perception patterns. For the lexicon model, a database of nearly 27,000 words produced by a single speaker is used to predict listener word recognition patterns when these words are embedded in noise in a series of six experiments utilizing different tasks (open, fill-in-the-blank recognition, and closed choice between two similar-sounding words) and different stimuli (naturally produced, enhanced, and degraded). The cue weights from these two model fits are then compared to address the first question. To answer the second question, simulations of noise added to different cues, and the resulting change in predicted similarity between sounds (in the inventory case) and words (in the lexicon case), are used to study the stability and adaptive response of each system to uncertainty in the acoustic signal. As such, these experiments will be able to address key claims about the structure and organization of sound systems in language.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.