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Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing

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Absolute:<br />

The standard reference sound pressure in air or other gases is 20 µPa, which<br />

is usually considered the threshold of human hearing (at 1 kHz).<br />

Actual Sound pressure →<br />

↖ Standard reference pressure 20 μMpa<br />

Absolute:<br />

Sound pressure level in dB as a ratio to<br />

standard reference in logarithmic scale.<br />

76db= 20log(P/20 μPa)<br />

Log(P/20 μPa)=3.8dB<br />

P= 10 3.8 x 20 μPa<br />

=126191 μPa<br />

http://www.ncvs.org/ncvs/tutorials/voiceprod/equation/chapter9/index.html

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