Abstract: An apparatus and method device for measuring at least one property of a board product, such as a paperboard product which includes a transmitter for applying a vibrational excitation to at least one region of the board product. The excitation includes a plurality of frequencies lying within a predetermined frequency range. The apparatus further includes a receiver for measuring a vibrational response of the board product to the vibrational excitation. A processor processes the measured vibrational response to obtain a frequency response of the region of the board product to the excitation, and analyses the frequency response to determine a measure of at least one property of the board product.