The relationship between abnormal respiratory sounds and flow rates was investigated. The respiratory sounds were recorded simultaneously with the flow rates from 9 children with asthma. The sounds were analyzed with continuous wavelet transformation (CWT), thereby yielding the sound amplitudes at each frequency that ranges from 100 to 1200Hz. Comparison between the sound amplitude and the flow rate in inspiration revealed that the sound amplitude in airflow acceleration was higher than in deceleration. The highest sound amplitude in both inspiration and expiration becomes lower as the frequency increases. These results indicate that the abnormal respiratory sounds are closely related to the respiratory flow rates.
