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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" Sound <strong>Level</strong>s<br />

Sound pressure level (SPL) or sound level is a logarithmic measure of the<br />

effective sound pressure of a sound relative to a reference value. It is<br />

measured in decibels (dB) above a standard reference level. The standard<br />

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

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

http://en.wikipedia.org/wiki/DB_SPL#Sound_pressure_level

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