BASICS OF ACOUSTICS: Main parameters of control & The first group of parameters: frequency – wavelength

Control parameters include the parameters of the method and the parameters  of the equipment that determine reliability of the results of the control. A measure of reliability is understood as the degree of error in the determination of various kinds of measured characteristics of a defect. Illiterate selection of the values ​​of the control parameters, in turn, leads to erroneous results of control and the skipping of the defective product for operation.
The parameters of the equipment depend on the characteristics of the flaw detector, converter, and scanning device.
The parameters of the method depend on the properties of the control object.

equipment method
Frequency, MHz Frequency, MHz
– Wavelength, mm
– Speed of a wave, m / s
Dimensions of the PET:
– beam exit point;
– the time of the wave in the PES;
– dimensions of the PET:
Angle of the prism, radius of the PEP.
Directivity diagram:
– angle of inclination AO;
– the angle of the NAM opening;
– angle of input;
– the boundary of the near zone.
Depth gauge accuracy The error in determining the coordinates of the reflectors
Zones of time selection:
– the beginning of the strobe;
– duration (end) of the strobe;
– method: echo, shadow
Control Zones



Conditional – Real
– Limit
– Equivalent
– Duration of the probe pulse;
– Duration of natural oscillations of the piezoceramic plate
Dead zone
Scan Settings:
– step;
– limits of PEP movement;
– scanning speed;
Search sensitivity.
Minimum conditional size of a fixed defect
– frequency of repetition of sounding pulses;
– Time of inertia and defect indicator
Minimum conditional size of a spoted defect
The resolution of the instrument – Resolution by distance (beam);
– Frontal resolution ability

6.1 The first group of parameters: frequency – wavelength

Frequency – the number of oscillations per unit time. It is the frequency that determines the attenuation of the wave in the monitoring object, the higher the frequency, the greater the attenuation.
The wavelength depends on the frequency and speed of the wave in the monitoring object, the shorter the wavelength, the smaller the defect is detectable. Because of the difference in the velocities of the longitudinal and transverse waves, their lengths also differ, the length of the longitudinal wave (2.36 mm) exceeds the length of the transverse (1.3 mm).