A pseudo-mastication sound presentation device to improve the texture of nursing care foods

The texture of foods is affected by concurrent auditory sensations. To improve the texture of nursing care foods, we developed a pseudo-mastication sound presentation device based on electromyogram (EMG) signals from the muscles of mastication. EMG signals have enabled us to promptly present care recipients with pseudo-mastication sounds. However, actual mastication sounds vary in intensity and duration more than EMG signals. Here, we investigated changes in EMG signals and actual mastication sounds during the mastication of two food types (rice crackers and Japanese pickles) to improve our device. We found that the intensity and duration of mastication sounds decreased as the number of mastication strokes increased. Furthermore, the intensity and duration of mastication sounds and the latency between the onset of EMG signals and the onset of mastication sounds also varied by food type. For EMG signals, only the intensity varied by food type. Based on our findings, we modified our pseudo-mastication sound presentation device to enable control of the intensity and duration of pseudo-mastication sounds based on the number of mastication strokes and food type. Reproducing more natural pseudo-mastication sounds can improve care recipients' motivation for ingesting nursing care foods, thus preventing malnutrition and frailty.