Vibrothermography is an effective non-destructive testing technique for detecting closed defects like cracks and delaminations through frictional heat generated under ultrasonic excitation. However, its accuracy is often reduced by standing wave patterns that create periodic temperature artifacts in non-defective areas, leading to false positives. To overcome this, we propose an image processing approach using 2D Fourier Transform (2D-FFT) to reduce SW-induced patterns in the frequency domain. This enhances defect visibility by suppressing unwanted heat signatures. The method is evaluated on a cracked PMMA plate and a hollow tube of the same material.