A method of measurement of the velocity of ultrasonic vibrations in structural units made of concrete by means of ultrasonic phased antenna arrays without the use of samples is described. In the methods signals are processed by means of a plane focusing algorithm designed for the detection of refl ecting planes. Results of measurements of the velocity of ultrasound in concrete are presented. Keywords: velocity of ultrasonic vibrations, plane focusing algorithm, ultrasonic tomography.Only unidirectional access to the surface of objects is possible in ultrasonic inspection of extended structural units made of concrete (structures for radiation and biological protection, enclosures, walls of buildings, etc.). This precludes the use of the direct-shadow method for measurement of thickness or determination of the velocity of ultrasonic vibrations in concrete and suggests the use of the less sensitive unidirectional echo method. However, the single-channel echo pulse method is not suitable for use in the inspection of extended (greater than 0.5 m) structural units due to a number of factors.First, anomalously high frequency-dependent damping of ultrasonic signals in concrete entails a reduction in the frequency of the probe signal down to ƒ 0 ≤ 100 kHz, which leads to widening of the directional pattern of the ultrasonic transducer and a decrease in azimuthal resolution and makes it impossible to precisely determine the coordinates of the refl ecting planes [1].Second, a priori information on the velocity of ultrasonic vibrations in concrete (in the measurement of thickness) or on the thickness of the article (for measurement of the velocity c lon of an ultrasonic longitudinal wave) is needed for the use of the ultrasonic echo pulse unidirectional method of measurement. However, standard samples of concrete cannot be used in inspection of domestic structural units for preliminary measurement of the velocity of an ultrasonic longitudinal wave, as a result of which the velocity of ultrasonic vibrations must be measured directly in the article.Domestic and foreign standards, which establish a technique of determining the strength of concrete by means of measurements of the longitudinal velocity of ultrasonic vibrations in concrete [2, 3], supply a number of different methods of measuring the velocity c lon without the use of samples; the relationship of c lon to the velocity of a surface wave c s may be established on the basis of these methods [4][5][6][7]. Such a relationship may be determined in rather simple fashion through the use of two piezoelectric transducers situated on the surface of the article at a fi xed distance b apart. The radiating piezoelectric transducer generates an acoustic pulse which propagates on the surface of the article being inspected and after time t = b/c s reaches the detecting piezoelectric transducer. The velocity of longitudinal ultrasonic vibrations is determined from the rate of propagation of the surface wave in the given substance: c lon = kc s , with the proportionality factor k mea...