Standard PAL CRT televisions scan horizontally at 15.625 kHz, while color NTSC sets run at about 15.734 kHz. Those rates sit close enough to the upper edge of human hearing for the electronics to become part of the room's sound.
The familiar squeal is not coming from the speaker. Magnetic parts in the horizontal deflection and high-voltage circuitry can vibrate while the set repeatedly sweeps the electron beam across the screen and snaps it back for the next line. Some sets barely whisper, while others make the tone obvious from across a quiet room.
Calling every version of it “flyback whine” is convenient, but a little too tidy. The flyback transformer is a common source, yet coils, ferrite parts, and the deflection yoke can also move enough to make audible noise. What you hear depends on the circuit, its mounting, and which parts happen to resonate.
For a 625-line, 50-field television system, two interlaced fields make one frame, giving 25 frames each second. Multiply 625 lines by 25 frames, and you get 15,625 line scans per second. The familiar PAL whistle therefore sits at 15.625 kHz because the picture timing puts it there.
Color NTSC timing is slightly different. Its field rate is about 59.94 Hz, with roughly 29.97 interlaced frames each second, placing the horizontal rate near 15.734 kHz. The gap between the two standards is only about 109 Hz, but it is a real shift rather than a cosmetic change in tone.
The flyback stage is tied closely to this horizontal rhythm because it has to generate high-voltage pulses during retrace. Repeated magnetic stress can make a transformer core or winding move by a tiny amount. Thousands of those movements every second are enough to turn an electrical timing cycle into an acoustic one.
A CRT deflection-yoke damping design specifically uses softer material around vibrating parts to reduce noise during operation. The design also describes audible output associated with 50 Hz and 100 Hz vertical-deflection drive, which matters because not every CRT noise you hear belongs to the 15 kHz whistle.
A lower buzz can therefore live beside the high tone. Mains-related hum, vertical-deflection vibration, loose magnetic parts, and cabinet resonance occupy different parts of the spectrum, so lumping them together hides useful clues. A clean 15.6 or 15.7 kHz tone and a rough midrange rattle are not the same fault wearing different clothes.
Age can change the balance without changing the television standard. Adhesives harden, mechanical joints loosen, and a part that once stayed quiet may start coupling its vibration into the chassis more efficiently. The electrical frequency can remain stable while the apparent loudness or texture becomes much more annoying.
Computer CRTs complicate the picture. VGA and later display modes commonly pushed horizontal scanning beyond 30 kHz, putting the fundamental well above the range most people can hear. A monitor can still buzz or rattle from other components, but it does not automatically carry the same 15 kHz signature as a standard-definition television.
This also explains why recordings of old televisions can sound different from what someone remembers in person. Microphones, sample rates, room reflections, and hearing sensitivity all affect whether the narrow high-frequency component survives. The physical set may be producing a stable line-rate tone even when one listener hears nothing, and another finds it impossible to ignore.
For sound design, the useful detail is precision rather than volume. A PAL-style CRT bed belongs around 15.625 kHz, while NTSC color timing points closer to 15.734 kHz, and lower buzzes should be treated as separate mechanical or power-related layers. Piling all of them onto one oscillator makes the result louder, but not more faithful.
The familiar squeal is not coming from the speaker. Magnetic parts in the horizontal deflection and high-voltage circuitry can vibrate while the set repeatedly sweeps the electron beam across the screen and snaps it back for the next line. Some sets barely whisper, while others make the tone obvious from across a quiet room.
Calling every version of it “flyback whine” is convenient, but a little too tidy. The flyback transformer is a common source, yet coils, ferrite parts, and the deflection yoke can also move enough to make audible noise. What you hear depends on the circuit, its mounting, and which parts happen to resonate.
The whine is locked to horizontal scanning
A standard-definition CRT builds the picture line by line. The horizontal deflection circuit drives the beam across one line, returns it, then repeats the cycle thousands of times each second. Its repetition rate is the horizontal line frequency, which is why the whistle lands in such a narrow high-frequency region.For a 625-line, 50-field television system, two interlaced fields make one frame, giving 25 frames each second. Multiply 625 lines by 25 frames, and you get 15,625 line scans per second. The familiar PAL whistle therefore sits at 15.625 kHz because the picture timing puts it there.
Color NTSC timing is slightly different. Its field rate is about 59.94 Hz, with roughly 29.97 interlaced frames each second, placing the horizontal rate near 15.734 kHz. The gap between the two standards is only about 109 Hz, but it is a real shift rather than a cosmetic change in tone.
The flyback stage is tied closely to this horizontal rhythm because it has to generate high-voltage pulses during retrace. Repeated magnetic stress can make a transformer core or winding move by a tiny amount. Thousands of those movements every second are enough to turn an electrical timing cycle into an acoustic one.
The flyback is not the only part that can sing
CRT deflection hardware contains more than one mechanically excitable part. Horizontal and vertical coils sit around the tube neck, ferrite cores shape the magnetic field, and supporting pieces hold the assembly in place. Alternating magnetic forces can make those components vibrate even when the picture looks perfectly normal.A CRT deflection-yoke damping design specifically uses softer material around vibrating parts to reduce noise during operation. The design also describes audible output associated with 50 Hz and 100 Hz vertical-deflection drive, which matters because not every CRT noise you hear belongs to the 15 kHz whistle.
A lower buzz can therefore live beside the high tone. Mains-related hum, vertical-deflection vibration, loose magnetic parts, and cabinet resonance occupy different parts of the spectrum, so lumping them together hides useful clues. A clean 15.6 or 15.7 kHz tone and a rough midrange rattle are not the same fault wearing different clothes.
Age can change the balance without changing the television standard. Adhesives harden, mechanical joints loosen, and a part that once stayed quiet may start coupling its vibration into the chassis more efficiently. The electrical frequency can remain stable while the apparent loudness or texture becomes much more annoying.
PAL and NTSC leave different acoustic fingerprints
The 15.625 and 15.734 kHz figures are useful because they tie a sound directly to video timing. A producer using the plugin's switchable PAL and NTSC whine is therefore changing a real timing fingerprint, not merely picking between two arbitrary high notes.Computer CRTs complicate the picture. VGA and later display modes commonly pushed horizontal scanning beyond 30 kHz, putting the fundamental well above the range most people can hear. A monitor can still buzz or rattle from other components, but it does not automatically carry the same 15 kHz signature as a standard-definition television.
This also explains why recordings of old televisions can sound different from what someone remembers in person. Microphones, sample rates, room reflections, and hearing sensitivity all affect whether the narrow high-frequency component survives. The physical set may be producing a stable line-rate tone even when one listener hears nothing, and another finds it impossible to ignore.
For sound design, the useful detail is precision rather than volume. A PAL-style CRT bed belongs around 15.625 kHz, while NTSC color timing points closer to 15.734 kHz, and lower buzzes should be treated as separate mechanical or power-related layers. Piling all of them onto one oscillator makes the result louder, but not more faithful.
