mark1101 Posted January 7, 2009 Share Posted January 7, 2009 I found this with my RTA setup when I was measuring my room. A spike right at 15.75Khz.......80 db at back of TV......72 db 12 ft. away in room. Ever hear of this? What can you do about it? A few love taps did nothing. Panasonic 36" tube TV about 10 years old working perfectly still. I can not hear it I can only see it on the screen. But I matched the volume of it at lower frequencies (using the signal generator) that I can hear and it must be pretty loud for my cats. Quote Link to comment Share on other sites More sharing options...
BEC Posted January 7, 2009 Share Posted January 7, 2009 Standard NTSC analog television has 525 lines that get put on the screen every 1/30th of a second. 525 X 30 = 15,750 hz. Bob Quote Link to comment Share on other sites More sharing options...
Islander Posted January 7, 2009 Share Posted January 7, 2009 I used to be able to hear that tone when I was younger. It sounded sort of like a high-pitched whistle. I could tell the TV was on without looking at it, but I don't hear the tone anymore. Quote Link to comment Share on other sites More sharing options...
BEC Posted January 7, 2009 Share Posted January 7, 2009 I can still hear it but not across the room from it like I once could. Now I have to be very close to the TV to hear it. Bob Quote Link to comment Share on other sites More sharing options...
russ69 Posted January 8, 2009 Share Posted January 8, 2009 I have not heard this in years, I can still hear the refer running....... Do the new TV's do this or just the old CRT's? Thanx, Russ Quote Link to comment Share on other sites More sharing options...
WMcD Posted January 8, 2009 Share Posted January 8, 2009 I agree with the above. As a youth (circa 1960) some few TVs (CRTs then) made the very high pitched noise. As Bob C. points out, all TV's had that potential because of the raster. Probably the variation in acoustic output was because of the physical structure of the deflection coils and even whether the glass tube or cabinet resonates or was providing acoustic insulation. Some computer monitors from 15 years ago made a very, very, faint whine and it was barely perceptable and would change with resolution (scan rate) settings. One odd thing is going on with my aging Compaq lap top. When the office is very quiet on weekends, with the HVAC shut down . . . I can hear some whine which shifts according to the image presented. It could be coming from the LCD panel, the electronics, or even the built-in speakers, The speakers are really tweeters by most standards. Wm McD Quote Link to comment Share on other sites More sharing options...
mark1101 Posted January 8, 2009 Author Share Posted January 8, 2009 Thanks for the comments guys. I also posted this in Home Theater since I didn't know who knew TVs. It got more interesting later in the evening. I got my 17 year old son to come down to the basement and I showed him the RTA display. He walked up to the TV and told me YES I can hear the high pitched tone. That it was not that loud really. He could also hear it from the sofa 12ft. away. So.......then we shut off the TV and used the RTA signal generator to do a little old man (48) / young man (17) hearing test. To make a long story short I can hear up to slightly over 16K but only when that tone is around 100 db......LOUD. I could hear the 15.7K tone at around 90db......but it is slightly quieter coming out of the TV and I had no idea it was even in existence all this time. At around 75db I could only hear up to about 14.4K. My Behringer mic is extremely sensitive and picks up sounds at quite a distance and I found this whole thing by accident. My son can hear out past 17K at around 75db. Much better than me. Quote Link to comment Share on other sites More sharing options...
Don Richard Posted January 8, 2009 Share Posted January 8, 2009 I have not heard this in years, I can still hear the refer running....... Do the new TV's do this or just the old CRT's? The newer digital sets operate differently, so I would not expect to hear this on them. The really old TVs, such as B&W sets, seemed to be louder than the newer CRTs are. Quote Link to comment Share on other sites More sharing options...
InnerTuber Posted January 8, 2009 Share Posted January 8, 2009 Mark - jam a couple of those orange traffic cones in yer ears and retest. You might hear the mice before the cat does! Quote Link to comment Share on other sites More sharing options...
JackDalton Posted January 8, 2009 Share Posted January 8, 2009 It's often the flyback transformer (that's used to generate the high voltage for the CRT). If you're lucky it has a clamp that can be tightened to reduce the noise. Sometimes a bit of shimming with a nonconductive material can help. But if you're not used to working inside a TV you might want to seek expert help - there's potentially lethal voltages present. It's also a great way to get thrown across the room. Regards Quote Link to comment Share on other sites More sharing options...
Coytee Posted January 8, 2009 Share Posted January 8, 2009 I don't hear the tone anymore. Yet the voices continue.... that's really too bad... you always seemed like such a normal person... [:^)] Quote Link to comment Share on other sites More sharing options...
oldtimer Posted January 8, 2009 Share Posted January 8, 2009 I hear a whine. A lot. Quote Link to comment Share on other sites More sharing options...
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