Proliferation of ultrasonic testing equipment has made measurements of compression and shear wave velocities in the laboratory more accessible. However, these equipment may have different operating frequency range, type and arrangement of piezoelectric crystals, and coupling of the piezoelectric crystals to the platens. This paper investigates the effect of frequency on wave velocity of unsaturated soil with various degrees of saturation. While the trend relating wave velocity to specimen's degree of saturation is well known, the effect of frequency still remains largely unclear despite various analytical derivations. Even though various experiments conducted using ultrasonic platens have shown velocity to increase with frequency, experiments conducted in this study showed otherwise. Fast Fourier Transform (FFT) of the receiver's signal for compression wave showed that frequency of the receiver's signal does not vary with the frequency of the signal supplied to the transmitter.
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