Nondestructive Testing Encyclopedia- Ultrasonic Testing - |

## 1. Wavelength | where: f = frequency c = acoustic velocity = wavelength | |wave length| |frequency| |velocity| |

## 2. Acoustic Impedance | where:
Z = acoustic impedance c = acoustic velocity= density of transmitting medium | acoustic impedance |acoustic impedance| |

## 3. Transmission Coefficient for Normal Incidence | where: Z= acoustic impedance in medium 1_{1} Z= acoustic impedance in medium 2_{2}D = transmission coefficient
| |transmission factor (coefficient) | |

## 4. Reflection Coefficient for Normal Incidence | where:Z = acoustic impedance in medium 1_{1}Z = acoustic
impedance in
medium 2_{2}R =
reflection
coeffcient | |reflection coefficient |

## 5. Snell's Law | where:
c = acoustic velocity in medium 1 _{1} c = acoustic velocity in medium 2 _{2} = beam angle in medium 1_{1} = beam angle in medium 2
_{2} |
Example |Snell's law| |

## 6. Near Zone | where: D = the diameter of a flat circular oscillator = wavelength of the ultrasound N = length of near zone
| |near field| |

## 7. Half Angle of Divergence (for flat circular oscillators) | where: - = half angle of divergence
k = constant based on stated dB drop from center maximum_{ dB } = wavelength D = the diameter of a net circular oscillator k vary for the dB drop that is to be determined. _{ dB } -1.5dB k=0.37 -3dB k=0.51 -6dB k=0.7 -10dB k=0.87 -12dB k=0.93 | beam spread |

## 8. Convergence PointFor determining the focal distance of a focused beam in a 2 media geometry.
| where: f = new focal distance
_{x}f = focal distance in coupling medium _{1}c = acoustic velocity in coupling medium _{1} c = acoustic velocity in second medium _{2} P = pathlength in the coupling medium_{1} | |convergence point| |

## 9. Sound Pressure | where: - = density
c = velocity of sound= angular frequency = particle displacement Z = c = acoustic impedance | |acoustic power density| |

## 10. Intensity of Acoustic Power | where: p = pressure= angular frequency = particle displacement Z = c = acoustic impedance normally in units of W/m ^{2} | |

## 11. Intensity Level## B = 10 log (J/J
| where: - J
_{o} is the arbitrary (10^{-12} W/m^{2}) reference level corresponding to the faintest
sound detectable by the ear.
Since J is proportional to the sound pressure squared, the difference between two intensity levels can be determined by; | |

## 12. Attenuation | where: - p
_{o} and p are sound pressures at the start and end of a length d.alpha is the coeffcient of attenuation for a given material alternatively; | |attenuation coefficient| |

Ultrasonic Inspection 2 - Training for Nondestructive Testing

E.A. Ginzel; Prometheus Press Canada.

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