How come the PC-screen vibrates / visually oscillates when I sit humming low tones?

I practice classical Indian music and am also a singer. When I sit in front of a PC with a tube (! it does not happen with LCD screens) I can make the image on the screen to oscillate, influencing the optical effect with the pitch of my humming. I suppose the image on screen has a particular intermittent frequency and that I create interference patterns likewise to what happens when tuning an instrument and you go from a pure interval slowly to a dissonant interval and back in to pure again. Question: at what frequency is the image built up on a tube-screen? Would changing the colours on the screen form say red to blue to green make a difference? What actually vibrates when I hum and this optical stroboscopic (?) is produced? My head, my eyes, my brain? All of the above? Find a tube-screen or try it on a TV-set, and start humming and explore your lower registers in slow sweeping movements. Observe closely, consider, and if you have anything to remark on, please do! cordially, martinHow come the PC-screen vibrates / visually oscillates when I sit humming low tones?
Intelligent answer…



Well assuming that your monitor isn’t broken the phenomena you report is possibly caused by harmonic resonance. Every item vibrates at a certain frequency. For example if you hit a bell it will vibrate and ring with a certain note. However if you play that exact note back to it, then the reverse happens and you can cause the bell to vibrate. This is called constructive interference. Basically if the sound waveform you are producing exactly matches the natural waveform of the object then the waves interfere with each other and cause the amplitude to increase, making the object vibrate. This is how singers can shatter glasses, its nothing to do with volume or hitting a “c”. It’s simply hitting the same natural note as the glass. It has also been seen to destroy bridges, and its why soldiers break rank when marching across bridges.



I presume that you are hitting the natural resonant frequency of something inside the monitor, causing the interference.



A tv will refresh at 50 Hz, a pc monitor usually 75 to 100 Hz, and LC monitor uses a different technology and doesnt flicker in the same way.How come the PC-screen vibrates / visually oscillates when I sit humming low tones?
The effect is within your eyes.



If you are over 45, have an eye test, as a precaution.
Wow. Just wow.
can you break glass? Or interfere with peoples head phones on the bus? I want this power
it's your eyes vibrating not the screen, try it with a witness and see if they see the vibration!