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Issues relating to the use of a 61.5 db conversion factor when comparing airborne and underwater anthropogenic noise levels. (In special issue on: the detection of buried marine targets)

Issues relating to the use of a 61.5 db conversion factor when comparing airborne and underwater anthropogenic noise levels. (In special issue on: the detection of buried marine targets)
Issues relating to the use of a 61.5 db conversion factor when comparing airborne and underwater anthropogenic noise levels. (In special issue on: the detection of buried marine targets)
Although a considerable amount of the current underwater acoustics literature deals with the proper documentation and analysis of underwater anthropogenic noise levels, mistakes and misconceptions can occur when attempts are made (often by non-experts) to make these data accessible for legislators, journalists and the public. This is because it is difficult for humans to assess qualitatively underwater sound level and quality. It can even be difficult for researchers to judge whether a given underwater sound should be classified as “loud” or “soft”. Many practitioners have suggested that the difference between airborne and underwater sound can be accounted for by applying a 61.5 dB comparison factor (in an attempt to compensate for the different acoustic impedances, and dB reference level conventions, which characterize acoustics in air and water). Whilst use of such a factor is preferable to use of none (which has led to misleading comparisons between levels in-air and water) nevertheless its existence could confer a false sense of security that the comparison is sound, whereas in fact, depending on the details of the comparison, a range of other issues would have to be rigorously taken in to account. Those issues include the perception of sound and annoyance underwater, and the problematic issue of making comparisons across species. This paper does not offer solutions to those issues, but rather outlines the thinking behind the 61.5 dB comparison factor, and shows the intriguing results of it blind application in some interesting example scenarios.
underwater acoustics, sonar, decibel, anthropogenic noise, snapping shrimp, bearded seal, bottlenose whale, strandings, marine mammals, cavitation in cetaceans
0003-682X
464-471
Finfer, D.C.
c2aa2745-6348-4149-904c-0dfcfe3da7a8
Leighton, T.G.
3e5262ce-1d7d-42eb-b013-fcc5c286bbae
White, P.R.
2dd2477b-5aa9-42e2-9d19-0806d994eaba
Finfer, D.C.
c2aa2745-6348-4149-904c-0dfcfe3da7a8
Leighton, T.G.
3e5262ce-1d7d-42eb-b013-fcc5c286bbae
White, P.R.
2dd2477b-5aa9-42e2-9d19-0806d994eaba

Finfer, D.C., Leighton, T.G. and White, P.R. (2008) Issues relating to the use of a 61.5 db conversion factor when comparing airborne and underwater anthropogenic noise levels. (In special issue on: the detection of buried marine targets). Applied Acoustics, 69 (5), 464-471. (doi:10.1016/j.apacoust.2007.05.008).

Record type: Article

Abstract

Although a considerable amount of the current underwater acoustics literature deals with the proper documentation and analysis of underwater anthropogenic noise levels, mistakes and misconceptions can occur when attempts are made (often by non-experts) to make these data accessible for legislators, journalists and the public. This is because it is difficult for humans to assess qualitatively underwater sound level and quality. It can even be difficult for researchers to judge whether a given underwater sound should be classified as “loud” or “soft”. Many practitioners have suggested that the difference between airborne and underwater sound can be accounted for by applying a 61.5 dB comparison factor (in an attempt to compensate for the different acoustic impedances, and dB reference level conventions, which characterize acoustics in air and water). Whilst use of such a factor is preferable to use of none (which has led to misleading comparisons between levels in-air and water) nevertheless its existence could confer a false sense of security that the comparison is sound, whereas in fact, depending on the details of the comparison, a range of other issues would have to be rigorously taken in to account. Those issues include the perception of sound and annoyance underwater, and the problematic issue of making comparisons across species. This paper does not offer solutions to those issues, but rather outlines the thinking behind the 61.5 dB comparison factor, and shows the intriguing results of it blind application in some interesting example scenarios.

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More information

Published date: May 2008
Keywords: underwater acoustics, sonar, decibel, anthropogenic noise, snapping shrimp, bearded seal, bottlenose whale, strandings, marine mammals, cavitation in cetaceans

Identifiers

Local EPrints ID: 51048
URI: http://eprints.soton.ac.uk/id/eprint/51048
ISSN: 0003-682X
PURE UUID: 23e0b70f-877c-411d-97a3-4c151703529d
ORCID for T.G. Leighton: ORCID iD orcid.org/0000-0002-1649-8750
ORCID for P.R. White: ORCID iD orcid.org/0000-0002-4787-8713

Catalogue record

Date deposited: 30 Apr 2008
Last modified: 16 Mar 2024 02:44

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Contributors

Author: D.C. Finfer
Author: T.G. Leighton ORCID iD
Author: P.R. White ORCID iD

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