Airguns are used for geological surveys of seabeds in order to detect and quantify the pres-ence and distribution of hydrocarbons. The approach is based on the emission of high pressure air bubbles from arrays of airguns. Acoustic waves are generated and the reflections from the seabed are picked up by hydrophone streamer systems. However, airgun blasts may induce behavioural problems in marine mammals and wild life due to their high power levels and the high noise propagation speed in water. The effect of the blast noise is often evaluated by advanced modelling packages such as range-dependent acoustic models or wavenumber integration methods. A new simplified approach is proposed for evaluating the effect of air gun blasts on marine mammals and wild life. Simple propagation equations are considered: they takes into account parameters such as the blast noise power, its spectrum, the distance from the single airgun, the bubble air volume, the water absorption coefficient, the distance from the seabed. The approach is based on simplifying hypotheses: seabeds are perfect lambertian reflectors with a 100% reflection coefficient. The frequency-dependent evaluation is introduced for determining the M-weighted levels at receptor points. The proposed procedure may be used for a preliminary evaluation of the noise effect on marine wild life because of the short estimation time and the easiness of use.
A simplified approach for evaluating the effect of airgun blast underwater noise on marine wildlife
ROSSI, Federico;NICOLINI, ANDREA;FILIPPONI, MIRKO
2012
Abstract
Airguns are used for geological surveys of seabeds in order to detect and quantify the pres-ence and distribution of hydrocarbons. The approach is based on the emission of high pressure air bubbles from arrays of airguns. Acoustic waves are generated and the reflections from the seabed are picked up by hydrophone streamer systems. However, airgun blasts may induce behavioural problems in marine mammals and wild life due to their high power levels and the high noise propagation speed in water. The effect of the blast noise is often evaluated by advanced modelling packages such as range-dependent acoustic models or wavenumber integration methods. A new simplified approach is proposed for evaluating the effect of air gun blasts on marine mammals and wild life. Simple propagation equations are considered: they takes into account parameters such as the blast noise power, its spectrum, the distance from the single airgun, the bubble air volume, the water absorption coefficient, the distance from the seabed. The approach is based on simplifying hypotheses: seabeds are perfect lambertian reflectors with a 100% reflection coefficient. The frequency-dependent evaluation is introduced for determining the M-weighted levels at receptor points. The proposed procedure may be used for a preliminary evaluation of the noise effect on marine wild life because of the short estimation time and the easiness of use.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
