Masking effects of speech and music: Does the masker's hierarchical structure matter?

Abstract

Abstract

Speech and music are time-varying signals organized by parallel hierarchical rules. Through a series of four experiments, this study compared the masking effects of single-talker speech and instrumental music on speech perception while manipulating the complexity of hierarchical and temporal structures of the maskers. Listeners’ word recognition was found to be similar between hierarchically intact and disrupted speech or classical music maskers (Experiment 1). When sentences served as the signal, significantly greater masking effects were observed with disrupted than intact speech or classical music maskers (Experiment 2), although not with jazz or serial music maskers, which differed from the classical music masker in their hierarchical structures (Experiment 3). Removing the classical music masker's temporal dynamics or partially restoring it affected listeners’ sentence recognition; yet, differences in performance between intact and disrupted maskers remained robust (Experiment 4). Hence, the effect of structural expectancy was largely present across maskers when comparing them before and after their hierarchical structure was purposefully disrupted. This effect seemed to lend support to the auditory stream segregation theory.

Sumario

El lenguaje y la música son señales que varían en tiempo y que están organizadas por reglas jerárquicas paralelas. A través de una serie de cuatro experimentos, este estudio compara los efectos enmascarantes de un solo hablante y de música instrumental en la percepción del lenguaje mientras se manipulaba la complejidad de las estructuras jerárquicas y temporales de los enmascaradores. Se encontró que el reconocimiento de las palabras por parte de los oyentes fue similar utilizando lenguaje jerárquicamente intacto o alterado o enmascaramiento con música clásica (experimento 1). Cuando se utilizaron frases como señal, se observó un efecto enmascarante significativamente mayor con lenguaje alterado que con lenguaje intacto o con enmascarador de música clásica (experimento 2), aunque no con jazz o enmascaramiento de música serial, lo que difrrió del enmascarador de música clásica en su estructura jerárquica (experimento 3). Al remover la dinámica temporal del enmascarador de música clásica o al restaurarla parcialmente, se afectó el reconocimiento de frases.; sin embargo, las diferencias en el desempeño entre los enmascaradores intacto y perturbado siguieron siendo amplias (experimento 4). Por lo tanto, el efecto de la expectación estructural estuvo muy presente en todos y cada uno de los enmascaradores cuando fueron comparados antes y después de que su estructura jerárquica fuera profundamente perturbada. Este efecto parece apoyar la teoría de la segregación del flujo auditivo.

Key Words:

• Hierarchical structure
• Temporal dynamics
• Speech perception
• Masking
• Music
• Auditory stream segregation
• Expectancy

Acknowledgements

The authors would like to thank Dr. Laura Koenig and Mr. Robert Aquino for their help throughout the length of the project, Ms. Keren Zahavi and Nadia Farooq for their contribution in signal processing for Experiment 4, and Drs. Qian-Jie Fu and John Galvin for their permission for the use of the IEEE sentences. The authors were deeply grateful of the constructive comments of the three anonymous reviewers and Dr. Kathleen Pichora-Fuller, the section editor, on an early version of the manuscript. The authors were in debt to all the participants who volunteered their time for this study. Experiments 1 and 3 of this project served as partial fulfillment for the second author's MS degree. Portions of this work were presented at the 2007 American Speech-Language-Hearing Association Convention in Boston, Massachusetts.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.