On definitions of signal duration, evaluated on close-range airgun signals.
J Acoust Soc Am
; 153(6): 3513-3521, 2023 Jun 01.
Article
em En
| MEDLINE
| ID: mdl-37382497
ABSTRACT
In impact assessments for underwater noise, the duration of a transient signal is often expressed by the 90%-energy signal duration τ90â%. Consequently, the rms sound pressure is computed over this duration. Using a large set of measurements on marine-seismic airgun signals, it is shown that τ90â% is often very close to the interval between the primary and secondary pulse (the bubble period) or a small integer multiple thereof. In this situation τ90â% is a measure of the duration of the relative silence between primary and secondary peaks, which is not the intended measure. Rarely, τ90â% quantifies the duration of the main peak, leading to a much lower value of τ90â%. Since the number of peaks included in τ90â% is sensitive to the nature of the signal, relatively small differences in the signal lead to large differences in τ90â%, causing instability in any metric based on τ90â%, e.g., the rms sound pressure. Alternative metrics are proposed that do not exhibit these weaknesses. The consequences for the interpretation of sound pressure level of a transient signal, and the benefits of using a more stable metric than τ90â% are demonstrated.
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2023
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Article