Laser Doppler vibrometry was used to measure the sound-induced tympanic membrane (TM) velocity, assessed near the umbo, in 56 normal hearing human subjects at nine sound frequencies. A second series of measurements was made in 47 subjects with sensorineural hearing loss (SNHL). Each set of measurements has features in common with previously published results. The measured velocity magnitude (normalized by the stimulus sound pressure) at any one frequency ranged among subjects by factors of 3-0.3 (+/-10 dB) from the mean and the phase angle of the normalized velocity ranged from +/-15 degrees around the mean at low frequencies to more than +/-200 degrees around the mean at 6 kHz. Measurements repeated after intervals of minutes to months were generally within 40% in magnitude (+/-3 dB) and 20 degrees in phase. Sources of variability included the effect of small differences in the location of the measurement on the TM and small static middle-ear pressures. No effects of stimulus level, ear sidedness (right or left), gender, age or the presence or absence of SNHL were found. These results provide a baseline normal response for studies of TM velocity with conductive hearing losses of different etiologies.