This 60 second video is frequency spectrum of a simulation of the signal the gravitational wave background from binary black hole and binary neutron star mergers would make in an ideal (noise-free) gravitational wave detector (such as #LIGO or #Virgo) which is sensitive to frequencies above 10 Hz. The average time between successive binary neutron star mergers is 13 seconds. Binary black hole mergers are less frequent, occurring every 223 seconds on average. Because of this, there is only one binary black hole merger starting at 20 seconds and ending at 34 seconds. The binary black hole is located at a redshift of 1.4 and is composed of black holes with intrinsic masses of 10 and 15 times the mass of the Sun.
Here is the image from original post:
The figure below is a visual representation of the audio file. It shows the temporal evolution of the detector strain in the absence of instrument noise as a function of time. The strain is a proxy for how much a gravitational wave causes the distance between the arms of the detector to shift. For more detail on the background signal from neutron stars and black holes see the main page.
How I made spectrum video visualization?
I took the source audio file: https://dcc.ligo.org/public/0146/G1702057/001/SymphonyOfTheUniverse_BNS+BBH.m4r.mp3
Then I created video visualization of audio spectrum by filtering it through ffmpeg, result video I synced with source audio again.
Here are the list of commands used:
- Create spectrum from audio:
.\ffmpeg.exe -y -i .\SymphonyOfTheUniverse_BNS+BBH.m4r.mp3 -filter_complex "[0:a]atempo=0.5,atempo=0.5,atempo=0.5,atempo=0.597,aresample=3500,showspectrum=s=1366x768:color=intensity:saturation=-1:scale=5thrt:gain=1,format=yuv420p[v]" -map "[v]" SymphonyOfTheUniverse_BNS_BBH-spectrum.mp4
- Sync spectrum video with source audio:
.\ffmpeg.exe -y -i .\SymphonyOfTheUniverse_BNS+BBH.m4r.mp3 -i .\SymphonyOfTheUniverse_BNS_BBH-spectrum.mp4 -r 25 -filter:v "setpts=0.0744*PTS"
It was not easy to create spectrum video with right length, so I manually picked aresample and chained a lot of atempo filters, also syncing was hard too cause of fine tuning of setpts filter.
Source: https://dcc.ligo.org/public/0146/G1702057/001/SymphonyOfTheUniverse.html
Wish you love that!
Thank you!