We investigate the potential of through-transmission ultrasound in noninvasive aspiration detection for bedside rehabilitation. In the present study, we used through- transmission ultrasound to investigate the waveform change in received signals caused by an aspirated object located at the posterior wall of the larynx, the most difficult type of case in the detection of aspiration. In a simulation study based on an X-ray CT image of the neck of a patient, the aspirated object adhered at the posterior wall of the larynx resulted in the waveform change of the received signal with a maximum amplitude of 4.3% compared with that of the received signal with aspiration. In an experimental study using a swine larynx ex vivo, an aspirated object resulted in the waveform change of the received signal with a maximum amplitude of 43.3%. These results indicate the high potential of through-transmission ultrasound in aspiration detection.