Table 2.
Units and abbreviations for quantities described in the text. Note that some authors have used units of dB re pref μPa2 for SPL and TOLs: this notational difference does not affect the numerical levels reported
| Term | Abbreviation | Units in air | Units underwater | Short definition |
|---|---|---|---|---|
| Sound pressure level | SPL | dB re 20 μPa | dB re 1 μPa | Sound level over specified frequency range as a single number |
| Power spectral density | PSD | dB re (20 μPa)2Hz−1 | dB re 1 μPa2Hz−1 | Standardised spectrum of sound levels across frequency |
| 1/3-octave band level | TOL | dB re 20 μPa | dB re 1 μPa | Coarse sound level spectrum with logarithmic frequency scaling |
| Sound exposure level | SEL | dB re (20 μPa)2s | dB re 1 μPa2s | Cumulative measure of sound energy |