Abstract: An ultrasound densitometer for measuring the physical properties and integrity of a member in vivo includes a transmit transducer from which acoustic signals are transmitted, and a receive transducer which receives the acoustic signals after they have been transmitted through the member and/or a material with known acoustic properties. The densitometer allows the physical properties of a member to be measured without having to determine the distance between the transducers. The densitometer is able to measure the physical properties and integrity of the member from the transit time of acoustic signals through the member and/or by determining the absolute attenuation of at least one specific frequency component of acoustic signals transmitted through the member.