Introducing environmental acoustics
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Many organisms have the ability to communicate by emitting sounds and subsequently can hear and interpret those sounds. This ability is one of the basic senses as this sense enables communication within and between species. In the environment sound plays an important role as an indicator of ecological activity as well as a determinant of ecological stress, especially when ecological systems are disturbed by natural occurrences like fire or human induced activities such as wetland draining. Sounds result from these physical or human induced actions and thus sound is thus a valuable ecological attribute.
Listening to sounds of bats, birds, amphibians, insects and other vocalizing organisms is a method used to document their presence and abundance. The presence or absence of these and other vocalizing organisms is recognized as important because their presence or absence can be indicative of quality of the environment. Rachel Carson recognized this fact long ago and wrote a book titled ‘Silent Spring’ which was a harbinger of the environmental movement in the United States. The listening organ, or ear in the case of humans, is an amazing sensor that can discern and interpret a myriad of acoustic signals. This auditory sensor can be substituted with the microphone, coupled to a recorder can capture and preserve a record of auditory signals. These simple tools can be used to hear species specific occurrence and abundance of vocal organisms and other sounds and is therefore one of the few sensors that can be used to document the occurrence of specific organisms based on their unique signals. From this information we can develop quantitative measures of acoustic diversity and potentially develop indices of biological diversity based on sounds of organisms. This can potentially provide a framework to forecasting ecological change. Measuring, interpreting and modeling ecological change over time using acoustics presents a set of compelling scientific challenges.
My research on acoustics is based on the vision that measuring, recording and analyzing acoustic signals that emanate from the environment can lead to new ecological insights about the interaction between organisms and their environment. The information garnered from such research can have an important message as it may provide humans with a better understanding of the importance of maintaining the integrity of the environment so that it can sustain the life support system for the organisms that live in it.
March 19th, 2006 at 6:17 am
Is anybody checking out this information?
August 24th, 2006 at 10:54 am
Yes. Just found your page on Jim Mesner’s sight. I provided recordings of katydids to Mr. Metzner about 8 yeras ago and periodically check out his web page.
I have been recording sounds of the north Florida swamps and forests for more than 10 years and using the sounds in my musical compositions.
Are those panels microphones?
Thanks!
May 14th, 2007 at 1:20 am
Hi Stuart, while I am not a scientist I am very interested in the world and it’s health. Mostly I miss the sounds of the crickets and birds I used to hear in the years gone by. It is scary to know that a lot of species are dissapearing from our world. I live in Canada and I see new animals arriving here from the USA from time to time. New bird songs and insect sounds are becomming more frequent.
How far off am I in thinking that this country’s climate is becoming more like the one you live in?
May 16th, 2007 at 5:24 pm
David
You are correct that the biological world is changing. I have found that sound is an excellent metric to measure such changes. I am interested in where you live in Canada. I was born in Winnipeg and worked in New Brunswick and Saskatchewan before moving to Michigan.
Birds and insects can respond rapidly to climate shifts and many have noted that the distribution of birds like the Cardinal and insects like the Japanese beetle have moved north. There is evidence of earlier arrivals by birds to their summer breeding grounds. What new sounds have you been hearing. How about setting up a recording station or doing some recordings where you are? I would be glad to listen to them to hear what you are hearing.
I am developing automated acoustic sensors to monitor changes in acoustics. I am also developing analytical systems to identify animals in the acoustic signals and an index of acoustics to determine habitat health.
Regards
Stuart
May 17th, 2007 at 12:03 am
As an infant, my father introduced me to a record of animal sounds used to assuage my incessant crying. it was the only thing that would help. Now I have a myriad of tapes, CD’s and sounds I have pulled off the internet that reveal the whistles, blips, caws and moos of birds, cats, frogs, etc. I guess i still need to hear these sounds. Much to the chagrin of my family, our home growing up has never been without the sounds of bird, barking, meowing, and other acoustic effects (Ted Nugent cat scratch fever was also a favorite).
So I have identified completely with your article. Stuart I would really like to hear an update regarding your ‘index’ of acoustics’. That would be an amazing reference tool for me. I consider myself very ‘auditory” in preference. Also my hearing is bad in one ear (Led Zeppelin’s fault) and I have to compensate when soft spoken people talk by reading their lips, I can hear certain insect noises completely and some weird noises others cannot hear. Sometimes I hear blips and beeps coming from far away that no one can detect Regarding these climate shifts you talk about and the noise as a detection of the range of life in an area, what have you got so far?
Rita Leal
December 26th, 2007 at 3:50 pm
Dear Rita
I am pleased you find the index of acoustic that we have been developing of interest. The index is a relatively simple approach to assist my students and me to interptet the world of acoustics. We are attempting to obtain a measure of the amount of natural sound and the amount of technological sound in a place. To do this we record samples of sound every 30 minutes for a 30 secord duration. The sounds are recorded in 16 bit monaural in the range of 0- 20,050 Hz. We then divide each sound into 11 frequency intervals. I chose 1,000 Hz (1 KHz) as the interval. We then compute the amount of power in each of the 1 KHz intervals.
Our investigations into the frequency range where various types of sounds occur, found that animals (birds, amphibians and insects, etc.) generally occur in the range of 2-8 KHz and that sounds made by technology (cars, trains, boats, airplanes, etc.) generally occur between 1-2 KHz. We call the biological sounds biophony (2-8 KHz) and the technological sounds) technophony (1-2 KHz). We ignore the range 0-1 KHz as this tends to be quite large and associated with backgound noise.
We can then compute a normalized ratio of the two measures so that the range of values is between -1 and + 1; where -1 is all technophony and +1 is all biophony. Here is an example to show how it works.
Locate= Nn
Date= 20061031
Time= 0600
L1= 62783.568
L2= 3.0882
L3= 13.5127
L4= 44.0612
L5= 1.3331
L6= 0.4067
L7= 0.0427
L8= 0.064
L9= 0.0169
L10= 0.0134
L11= 0.0065
Indices
L13= 3.0882 (Technophony) L2
L14= 59.4204 (Biophony) L3+L8
L15= 0.9012 (L14-L13)/(L14+L15)
It this case the sound sample reveals that the location sampled has a value of 0.9012 which indicated a high degree of biophony. Now we can examine this trend over a day, month, or year to examine change.
I hope this helps answer your question. if you go to my developing website you can look at the Heartbeat of the City project and explore some of these relationships and hear sounds.
http://sonic.cevl.msu.edu
Regards
Stuart
February 4th, 2008 at 8:38 am
Hi, I’ve been meaning to investigate your web page ever since I heard about your research on NPR (Science Friday?). I love the way you’ve automated the data collection process.
I’m a (semi-) retired physicist who worked on rotation sensors (RLGs and Fiber Optic Gyros (FOGs) mostly. I confess I don’t quite understand your normalization process. Looking at the “Indices” you compute (above) I just think you may have made a typo - for example, L15 = 0.9012 (L14 - L13)/(L14 + L15). Is that a recursive evaluation for L15? Also, I’m assuming L1 thru L11 represent the 1 kHz frequency bins you mention. But the expression for L14 seems to only take L3 and L8 into account. Did you mean the sum from L3 to L8? I’m also curious how you account for the difference you’d get when you compare the power in one freq band (1 to 2 kHz) with the power over the 2 to 8 kHz bands.
This is very cool, though. Despite my ignorance
So you’re basically looking at how the mix of biophony and technophony varies over time? Maybe expecting a change due to “encroaching civilization?” That would indeed be interesting and significant.
I have an interest in “nature sounds” for another reason. I have a web site where I attempt to sell a program for the Mac that I wrote called “SonicMood” (www.sonicmood.com). In the program I include some recorded nature sounds with foreground sounds of MIDI instruments which add a kind of relaxing ambience. Because of my involvement in making this I’ve become somewhat more attuned to what I hear just walking out in the yard. We live in the Sierra Nevada foothills (very rural) and those sounds surround us.
February 6th, 2008 at 12:15 am
Just to let you know that I am including a summary of your project in an Intro to Environmental Science course I lecture in at College of Southern Nevada.
While I don’t anticipate any of these students will become scientists, they can benefit from an exposure to scientists and others innovate to describe the world more effectively.
Thanks for the work.
February 6th, 2008 at 12:15 am
Just to let you know that I am including a summary of your project in an Intro to Environmental Science course I lecture in at College of Southern Nevada.
While I don’t anticipate any of these students will become scientists, they can benefit from an exposure to scientists and others innovate to describe the world more effectively.
Thanks for the work.
February 6th, 2008 at 6:47 pm
Thanks for the interest in our research on acoustics. I made typos in response to Rita’s question (pointed out by John Hall (above)). Here are the corrections.
L13=L2
L14=L3+L4+L5+L6+L7+L8
L15= 0.9012 (L14-L13)/(L13+L14)
Stuart
April 6th, 2008 at 8:19 pm
Stuart:
Old birdwatcher interested in establishing a modest acoustic receiver base to “pipe” nature into my home. Haven’t the faintest idea where to start.
Any suggestions, and thanks.
Andy