Componentes do sinal acústico da deglutição: estudo preliminar

Abstract

The software allowed the visualization of three bursts during the swallowing of healthy individuals, and showed that the swallowing signal in normal subjects is highly variable.

Dysphagia Screening: Contributions of Cervical Auscultation Signals and Modern Signal-Processing Techniques

“…While some place it as low as 0.1 Hz in order to maintain a “pure” signal [21], [49], [51], [65], [66], [83], [86], [90], others place it as high as 30 Hz or more in order to eliminate motion artifacts and other low frequency noise [39], [42], [44], [60]–[62], [69]. Since similar bandlimits have yet to be identified for swallowing sounds, studies which use a microphone simply limit the recorded signal to either the human audible range [21], [32], [33], [37], [40], [46], [48], [67], [76]–[78], [86], [89], [95], [97]–[100], [102], [103], [110], [112]–[116] or the range of common stethoscopes used in bedside assessments [13], [22], [28], [39], [56], [69], [73], [88], [91], [92]. Typically, this bare minimum amount of signal processing has traditionally been done for one of two reasons.…”

“…First, studies that make extensive use of subjective human judgements, whether to determine the start and end times of individual swallows or to match physiological events with the time domain signal, do not want to filter out important frequency components and alter the signal. Instead, they attempt to provide a signal that is identical to what these experts would observe when performing a bedside evaluation in a clinical environment [19], [22], [28], [46], [48], [84], [91], [92], [106], [110]. Second, many of these studies look at only the most basic of signal features, such as the sound composites representing the number of swallows over time, the timing of swallowing phases, or simply the onset/offset of a swallowing event [14]–[17], [20], [27], [32]–[34], [36]–[40], [50], [52], [55]–[57], [68]–[70], [93], [95], [100]–[105], [107], [108].…”

“…The first analysis method is the most simplistic and extracts the most basic features and conclusions from the time domain recordings. For example, researchers have matched certain visual landmarks of a raw cervical auscultation signal with some specific physiological events [19], [37], [48], [69], [103], determined the onset and duration of a swallow [34], [68], [69], [94], [95], [97], [101], [110], [113], [114], or simply counted the number of swallows that occurred over a certain period [40], [95], [102], [104], [107], [111]. The second analysis method also uses simple features of the signal, but uses the subjective opinion of a trained expert listening to the acoustic signal rather than the researcher’s visual analysis of the signal waveform.…”