A new type of algorithm based on a modified least‐square method has been developed to analyze ultrasonic absorption for a single relaxation. Compared with the usual heuristic methods, this technique is a more direct one, which enables us to determine with high accuracy the relaxation parameters from a single initial estimated value of the relaxation frequencyfc. Computer simulation of the α/f2vsfcurves are presented for various conditions. This method is satisfactorily applied to the ultrasonic absorption of propionic acid over a frequency range from 2.8 to 95 MHz.