just wondering
2007-07-02 12:12:47 · 3 answers · asked by macgyver 1 in Science & Mathematics ➔ Engineering
you must have good ears. the frequency is the horizontal scan frequency, just over 15kHz. something in the set is vibrating because of the scan current, the usual culprit is the flyback transformer, but other components can do this as well or it could be HV leakage since a CRT derives its HV from the horizontal scan circuit. LCD TVs don't use any large sized components in the horizontal circuits or HV, so they rarely can generate enough vibration to be heard.
2007-07-02 17:12:46 · answer #1 · answered by lare 7 · 1⤊ 0⤋
Hi. The electron beam is controlled by electromagnetic coils. The beam sweeps across the screen 60 times per second (30 for every even line and 30 for every odd). This results in a scan rate that is around 15,750 times per second. The coil can emit a bit of sound during these sweeps and this is the 'whistle' you hear.
2007-07-02 12:18:14 · answer #2 · answered by Cirric 7 · 2⤊ 0⤋
You are hearing the output of the dislay's horizontal output driver/oscilllator which runs at 15,000 + Hertz or 15,000 + cycles per second
2007-07-02 14:59:04 · answer #3 · answered by Matt D 6 · 2⤊ 0⤋