Definition and Clinical Implication of Temporal Fine Structure / 대한이비인후과학회지

Perception of sound is associated with the use of multiple acoustic cues in the human auditory system. These acoustic cues can be classified by their temporal and spectral properties. Temporal information can be considered as a slowly varying envelope (ENV) superimposed on a more rapid temporal fine structure (TFS). Various sound-processing techniques have been developed to assess the role of acoustic information carried by temporal ENV and TFS information. Previous studies demonstrated that ENV cues are associated with speech recognition in quiet, while TFS cues have a role to melody/pitch perception and listening to speech in a competing background noise. Besides, a number of studies have shown that the relative insensitivity of hearing-impaired subjects to TFS information. Although current technologies used in cochlear implants are not efficient in delivering the TFS cues, new speech processing strategies have been proposed to deliver TFS information. We herein review the cutting edge of TFS related studies and discuss the clinical implication of TFS.

Research progresses of relative importance of temporal envelope cues in different frequency regions / 上海交通大学学报（医学版）

Based on the dominant fluctuation rates, the speech information in temporal domain could be divided into temporal envelope, periodic fluctuation information and temporal fine structure. Temporal envelope cues are essential for speech recognition, which could be transmitted to cochlear implanters by cochlear imlpants. The roles of temporal envelope cues from various frequency regions in speech recognition are diverse. Influenced by the testing materials, research methods, listening backgrounds and the parameters used to extract temporal envelope, the relative weights of temporal envelope across frequency regions would change accordingly. The research methods as well as their advantages or disadvantages and research results of relative weights of temporal envelope cues in different frequency regions are reviewed, and the possible reasons why the relative weights of temporal envelope cues in different frequency regions for non-tonal language and tonal language were different were discussed simply.

What Is Temporal Fine Structure and Why Is It Important?

Complex sound like speech can be characterized as the sum of number of amplitude-modulated signals representing the outputs of an array of narrow frequency bands. Temporal information at the output of each band can be separated into temporal fine structure (TFS), the rapid oscillations close to the center frequency and temporal envelope (ENV), slower amplitude modulations superimposed on the TFS. TFS information can be carried in the pattern of phase locking to the stimulus waveform, while ENV by the changes in firing rate over time. The relative importance of temporal ENV and TFS information in understanding speech has been studied using various sound-processing techniques. A number of studies demonstrated that ENV cues are associated with speech recognition in quiet, while TFS cues are possibly linked to melody/pitch perception and listening to speech in a competing background. However, there are evidences that recovered ENV from TFS as well as TFS itself may be partially responsible for speech recognition. Current technologies used in cochlear implants (CI) are not efficient in delivering the TFS cues, and new attempts have been made to deliver TFS information into sound-processing strategy in CI. We herein discuss the current updated findings of TFS with a literature review.