Spectrograms – Seeing Sound
Try describing the sound of a wind turbine.
Those of us who live next to wind turbines will notice the distinctive noises they produce but are reduced to using inappropriate words to describe it.
Woosh, swish, twack, yee yaw, churn…
Theses are comic book words to describe a physical and audible effect. When the sound of a turbine becomes an annoyance the noise becomes nuisance - comic book descriptions to describe unwanted sounds are inadequate. When trying to describe to our Environmental Health Officer why the neighbours turbine was causing us trouble and talking of the woosh, the weesh and the twack of it reduced what is a very real problem to hilarity.
Humans are visual beings. It occurred to me that perhaps we could understand the sound of a turbine though images and the exploration of Spectrograms began. Wikipedia describes a spectrogram as “a visual representation of the spectrum of frequencies in a sound or other signal as they vary with time or some other variable.” In other words a spectrogram is a picture of what we hear - a sound image.
In the audio industry record producers are increasingly using Spectrograms when mastering sound recordings to understand what happens when particular sound frequencies combine. Every instrument and machine or in this case a neighbours turbine produces specific sound frequencies that create an acoustic signature. The Endurance E3120 is known to produce tones in at 287.2 Hz, 955.2Hz and 2307.8Hz frequencies, and so by using a spectrogram and knowing what frequencies to lookout for you can show turbine noise sceptics what it is you are hearing at any time of the day or night, indoors and out.
If you would like to participate….
If you live next to an Endurance E3120 and want to to see what noise looks like then ….
Install smart phone app using NCH Software - WavePad app v 5.94 on (see links to software downloads below)
Record the turbine
The saved file is then opened up in iZotope RX4 software on a laptop.
You can save the screen shots as image files during the free 10 day demo, which you can download to use full features.After 10 days you can open and see files but you only get 30 seconds of sound and you have to use the printscreen button on your computer to save the screen shot
install Sonic visualiser (v2.3.91/v2.4beta) on your laptop. This is a free program from Queen Mary University London and you can view spectrograms and hear the audio with no limitations
Useful links/Software Downloads:
NCHSoftware - http://www.nch.com.au/wavepad/index.html
WavePad - app from Playstore (Google)
iZotrope RX4 - https://www.izotope.com/en/products/audio-repair/rx/
Sonic Visualiser (v2.3.91/v2.4beta) - http://vamp-plugins.org/forum/index.php/topic,255.msg580.html?PHPSESSID=469elta366e21f9iqdven2ri45#msg580
Whichever sound recording method you use, keep a noise diary too, noting down times, dates and general observations on the prevailing weather conditions
NB – if you are living next to an Endurance 3120, and you have either made recordings in wav format, or would be willing to give it a try, please visit my web site
The spectrograms produced by the above methods don't at the moment give an accurate sound level, just a picture of sound frequencies that can be heard.
However, if this method can be used to show what the typical background environmental noise 'looks' like prior to an E 3120 (or any other) turbine being installed, it will be a record of what the background sound picture and frequencies were before construction.
Not only might it then enable challenges to be made to the developers assumptions regarding background noise, but environmental health officers could also find it useful when dealing with future complaints.
Unfortunately experience shows that acoustic consultants, who are increasingly being employed by turbine developers are turning away requests for independent acoustic surveys. The cost of buying or hiring calibrated recording equipment and sound level meters is prohibitive so the only option is to improvise and experiment. Though this tool at the moment is not rigorous enough on its own to be accepted by Environmental Health Officers as proof of wind turbine noise nuisance it does show what can be heard, when and where.
The next step is to produce evidence in a format that can be accepted by Environmental Health as proof that a noise nuisance problem exists. Perhaps if other neighbours to E3210s can produce their own sound pictures we will accumulate enough data to show Endurance that the acoustic signature of their turbine is a nuisance.
With acousticians and EHOs not listening perhaps a future class action against a manufacturer will clear the turbine sceptics ears.