After further consideration I have decided to focus on noise pollution in the ocean. The article this week is of course on noise pollution but more towards natural sound. It starts by saying all the noises in the ocean make up ambient noise and they can be categorized by frequency. The ambient noise frequency ranges between 20 Hz and 500 Hz when no boats are present however the sounds of distant shipping is still picked up. In the frequency range of 500-100,000 Hz most of the noise comes from spray and bubbles due to crashing waves and this increases due to the wind velocity. Also at frequencies over 100,000 Hz is something called thermal noise which is the movement of water molecules. Now there are sources of natural noise in the ocean. High noises, usually read in decibels at one meter, consists of things like lighting striking the surface of the water which has a reading of 260 dB at 1 meter. Also an underwater volcanic eruption carries a reading of 255 dB at 1 meter. The sounds produced by marine animals are many. Marine mammals , such as blue whales and harbor porpoises, produce sounds over a wide frequency range, from less than 10 Hz to over 100,000 Hz which is the range that they can hear as well. Marine mammal calls can actually increase ambient noise levels by 20-25 dB in some locations at certain times of year. Blue and fin whales produce low-frequency moans at frequencies of 10-25 Hz with estimated source levels of up to 190 underwater dB at 1 m. being that marine mammals use such a large frequency range it's easy to see how an overwhelming amount of noise from boat traffic, sonar, drilling platforms, and natural noise can drive marine mammals crazy. If you like explore the site below but make sure you go to the
audio gallery and listen to all the cool noises like lighting hitting the water and underwater volcanic eruptions.
http://www.dosits.org/science/soundsinthesea/commonsounds/?CFID=2338580&CFTOKEN=59542381
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| noises by marine species |
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| common noise in the ocean plus man made noise |
Deb'n Paul:
If you are interested in this topic, then I have a few questions that I'd like answers to. First--what is a hertz and how does that differ from frequency and decibel? Second--I'd certainly want to learn more about the differences between the hertz/decibel levels of the various forms of ocean noise pollution sources and how they compare to the levels at which marine animals voice/hear. Great topic!!
To start hertz are the units used to measure frequency. To understand Hertz you must first understand frequency which is a concept discussed in periodic motions of objects. in turn these two work hand in hand as the frequency increases so does the Hertz. The unit decibel is directly connected to the intensity of a wave like how loud the persons speakers are in the car next to you. The decibel value is the logarithmic ratio of the intensity of the wave to a certain reference point.
Second Here are some tables that will help you understand what range marine mammals can here and produce. also a chart on common noise pollution sources.
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| this one is man made noise pollution. |
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| this is natural marine noise. |
Angela Boney:
Is this something you would be interested in further researching and using for your Research Project?
Yes Angela I am very interested in this and I am already in the process of building a hydrophone so I can start collecting some noise.
Ok--I need more elaboration on the questions you answered for me this week. Please remember--you will often times need to answer these questions to persons not at all familiar with these concepts/terms such as students in an intro oceanography class!. e.g., " The decibel value is the logarithmic ratio of the intensity of the wave to a certain reference point." followed by a link for me to continue searching for the answer. No, no, no! Again I ask--and in layman's terms--what is meant by hertz, frequency and decibel and how do they differ from one another. Also--if you are going to direct the student to more information, please help them out by giving them an example of how the information might be used or what you will be using it for. YOU do the work--that's your job! Not the job of the reader!
ReplyDeleteAlso--kudos for building your own hydrophone. For your next article review I'd love for you to talk about the instructions you used to build it an include some pics of you doing the building. I'd also like to know how sensitive is your hydrophone?--and how might you determine its sensitivity?
This may be the same type of question Dr. Woodall asked, but during any future presentation I would definitely be asking how your hydrophone compares to one purchased from a store. Maybe you could use yours and one made by a company (borrowed form Dr. Woodall?) out in the field as comparison? If you could record the noise yours picks up versus what a mass manufactured one pics up and play the audio during the presentation, that would be even better.
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