ultrasonics makes use of the correlation of continuous signals
rather than pulse-echo or pitch-catch techniques.
Spread spectrum ultrasonics is a patented new broad band spread-spectrum
ultrasonic nondestructive evaluation method. In
ultrasonics makes use of the correlation of continuous signals
rather than pulse-echo or pitch-catch techniques.
Spread spectrum ultrasonics is a patented new broad band spread-spectrum
ultrasonic nondestructive evaluation method. In conventional ultrasonics,
a pulse or tone burst is transmitted, then received echoes or
through-transmission signals are received and analyzed.
In spread spectrum ultrasonics, encoded sound is continuously
transmitted into the part or structure being tested. Instead of
receiving echoes, spread spectrum ultrasonics generates an acoustic
correlation signature having a one-to-one correspondence with
the acoustic state of the part or structure (in its environment)
at the instant of the measurement. In its simplest embodiment,
the acoustic correlation signature is generated by cross correlating
an encoding sequence, with suitable cross and auto correlation
properties, transmitted into a part (structure) with received
signals returning from the part (structure).
Section of biphase modulated spread spectrum ultrasonic waveform
Multiple probes may be used to ensure that acoustic
energy is propagated through all critical volumes of the structure.
Triangulation may be incorporated with multiple probes to locate
regions of detected distress. Spread spectrum ultrasonics can
achieve very high sensitivity to acoustic propagation changes
with a low level of energy.
Two significant applicat