Distance from Source to Reach 180/170 dB Intensity Level

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SUMMARY

The discussion centers on calculating the distance from a sound source in seawater required for the intensity level to decrease from 237 dB to 180/170 dB. The equation used is SPL = 237 - 25.35 log(R), where SPL represents sound pressure level and R is the distance from the source. The user initially calculated a distance that appeared too low, suggesting a safe distance for marine mammals should be around 500 meters. Factors such as wavelength absorption, sea depth, and reflections also influence sound intensity in water.

PREREQUISITES
  • Understanding of sound pressure level (SPL) calculations
  • Familiarity with logarithmic scales in acoustics
  • Knowledge of underwater acoustics and sound propagation in seawater
  • Basic principles of marine mammal auditory systems
NEXT STEPS
  • Research the effects of different wavelengths on sound absorption in seawater
  • Study the impact of sea floor topography on sound propagation
  • Explore the role of reflections in underwater acoustics
  • Learn about safety distances for marine mammals in relation to underwater noise
USEFUL FOR

Marine biologists, acoustic engineers, environmental scientists, and anyone involved in studying the impact of underwater noise on marine life.

JoaoCorvina
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Not a homework... simple curiosity by trying to know this a bit better in order to learn and understand possible effects of sound to marine mammals auditory systems.
In sea water, at distance of 1m from a localized sound source, you measure the intensity level as 237 dB.
How far away from the source must you be for the intensity level to fall to 180/170 dB? I am trying to do this but i come up with distances that don't seem right to me...

Been using this equation taken from http://www.underwaternoise.org.uk/measuring_noise/source_level.shtml

SPL = 237 - 25.35 log(R)

by replacing SPL with 180 dB, R comes up with a ow value for the distance which shouldn't be that low... it should be around 500m, distance that we consider to be safe for marine mammals.

Am I doing it right?

Would appreciate some help and some explanations!
 
Physics news on Phys.org
~180m is not so far away from 500m, especially with a logarithmic scale. With 170dB, it is very close to 500m, and some safety factor is always a good idea.

In addition, several factors can change the formula:
- different wavelengths can have different absorption in water
- if the depth of the sea is not large compared to the horizontal distance, the floor can be relevant.
- reflections elsewhere can be relevant
- ...
 

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