Can CRT's generate ultrasound?

[Emultra]

My own CRT occasionally emits a very high pitched noise sometimes, not that often but probably high pitched enough to prevent it being heard by a lot of people in their mid to late thirties and older (I'm 22).

Which makes me wonder, can CRT's generate sound of ultrasonic frequencies? If yes that might be something to consider (against) when buying a new monitor, which I'll probably have to do soon.

 

[videogames101]

Uh, I can hear a CRT TV turn on from across my house, they sound like a bitch, around 14khz, but idk if crt monitors are as bad.

 

[0roo0roo]

why are you still buying crts?
http://answers.yahoo.com/quest...=20070107084554AAMimP9

 

[MichaelD]

Like Videogames101, I can also hear a CRT running from quite a distance away. It can be very distracting. After a lot of reading I found out that the high-pitched "eeeeeeeee" I hear is actually the coils around the CRT (or in it, someplace) vibrating.

CRTs a dead technology. They use more power, generate more heat and weigh 5x as much as an identically-sized LCD screen.

 

[0roo0roo]

or the transformer apparently can make a high pitched noise as well.
and yea, i can hear it. quite annoying

 

[Howard]

You can't hear ultrasound.

 

[Emultra]

"You can't hear ultrasound."

Nope, but because it can be harmful, it's all the more relevant to know whether it's there.

As for why I choose CRT, the picture quality and responsiveness are still unmatched. Price is a factor as well. But I might go LCD, not sure.

 

[0roo0roo]

thats old info. newer lcds esp ones that will be led are pretty damn good.
any crt you buy now for cheap will be cheap tat that won't have the supposed advantage of crt. and professional ones will cost a fortune. crt is no longer competitive in any way.

 

[RebateMonger]

High pitched sounds are frequently attributed to the flyback transformer in CRTs.

 

[Howard]

Originally posted by: Emultra
"You can't hear ultrasound."

Nope, but because it can be harmful

WTF?

 

[Roguestar]

^ I think he means "nope, you can't, but" in that context.

 

[Howard]

Originally posted by: Roguestar
^ I think he means "nope, you can't, but" in that context.

Since when has ultrasound ever been harmful? Everything produces ultrasound to a certain degree. I mean EVERYTHING. I'm sure even the human body produces ultrasound.

 

[nineball9]

Originally posted by: RebateMonger
High pitched sounds are frequently attributed to the flyback transformer in CRTs.

True for TV's using CRT's. NTSC flybacks operate with a sawtooth waveform of around 15.7 kHz; PAL and SECAM use slightly different frequencies, all of which are above my hearing range. (Looked up your Wikipedia link - actual NTSC frequency is exactly 15,734 Hz.)

Modern computer monitors with CRT's operate at much higher frequencies (30 kHz- 150 kHz according to Wikipedia.)

There are other components/modules in TV's and monitors which can produce high frequency sounds - a switched mode power supply for example.

As Howard (and others) noted, "ultrasonic" is, by definition, any sound frequency beyond the upper range of normal human hearing, which is 20 kHz.

I had an echocardiogram done a few months ago. Being curious about the technology, I spent most of the procedure chatting with the tech about the sound frequencies etc used in echocardiology. I had a simple echocardiogram which uses a transducer which operated around 7 mHz (!) and when he was finished with me, he was off to the OR to do some 3D echocardiology which uses a transducer operating at 30 mHz. (!!) Aparently, the trandsducers cost a fortune.

I imagine that at extreme levels, ultrasonic frequencies might be harmful to the human body, but not at the levels found in TV's or monitors. Plug-in "pest control" devices emit ultrasonic frequencies (I have no idea how effective they are though.) Old remotes for TV's, garage doors and similar devices used ultrasonic transducers. Bats, mammals like us, use "echolocating sounds commonly range in frequency from 40,000 Hz to 100,000 Hz".

 

[corkyg]

A worthwhile read on the subject.

US

I have always been able to hear the high frequency "whistle" of CRT displays.

 

[Emultra]

Originally posted by: 0roo0roo
why are you still buying crts?

Reply from mpilchfamily in my other thread: "Problem is you almost can't find CRTs anymore. But the fact is a CRT is far superior in performance and image quality then any LCD or Plasma screen ever made. Typically an LCD with a 5ms response time or lower is best suited for gaming. But if you can find a CRT and don't mind the weight and bulk then i say go for the CRT."

 

[corkyg]

Add to weight and bulk, more heat and higher energy consumption.

 

[0roo0roo]

plus the supposed superiority is not really there in reality. the picture quality of modern lcds is pretty incredible, and you aren't going to get a 24" crt at a decent price these days. let alone a 30". any crts left are low end junk, any medium range consumer units had their factories close down long ago. and well that was years ago, by now crts are gone from most stores, even at the super low end. and no, used is not good for crt, they fade.