Ultrasonic velocity and absorption were measured in liquid furan (C4H4O), thiophene (C4H4S) and pyridine (C5H5N) over a frequency range from 70 to 700 MHz with high‐resolution Bragg reflection technique [K. Takagi et al., J. Acoust. Soc. Am. 62, 354 (1977)]. The results were described as vibrational relaxation phenomena. In furan and thiophene, all the vibrational modes relax in a single process at 120 and 320 MHz, respectively, at 20 °C. While in pyridine, two relaxation regions were found in a velocity dispersion curve up to 7 GHz, which was obtained in an experiment made cooperatively with Brillouin scattering. Quantitative analysis suggests that all above the third vibrational mode (605 cm−1) relax at 760 MHz, and the lowest (375 cm−1) and the second (405 cm−1) modes, at 3.9 GHz. This type of vibrational double relaxation has already been found in liquid benzene, dichloromethane, and dibromomethane.