In this paper, attenuation values are obtained from seismic data using
instantaneous frequency matching and spectral ratios. To obtain diffe
rential t values using instantaneous-frequency matching, a near offse
t reference pulse is attenuated until the resulting instantaneous freq
uency matches the observed value at the receiver. Prior to matching, f
iltering can be applied to each trace in order to reduce the effects o
f noise on the calculated instantaneous frequencies. In the second met
hod, the spectral ratio between a receiver pulse and a reference pulse
is used to obtain differential t values. To obtain an unbiased estim
ate, a variable spectral bandwidth is used depending on the noise leve
l of the data. The two methods are tested using synthetic traces and t
hen applied to crustal refraction data from the 1986 PASSCAL Ouachita
experiment. Results show that the differential t values obtained usin
g filtered, instantaneous frequency matching are consistent with and h
ave less scatter than those obtained from spectral ratios with a varia
ble bandwidth.