[ScientificSorcerer (OP)]

How do you make a quiet Tesla coil? when it's not overpowered, The only part of the device that makes a loud irritating noise is the spark gap. I hate the spark gap, is it possible to make a tesla coil without the spark gap? or at least one that makes little to no noise.

I was thinking of havig the device ultra high frequency so that the spark gap would make ultrasound would that work?

[evan_au]

The snap, crackle and bang of an electric arc is due to the current finding a new path through the air, instantly heating the air from room temperature to a plasma, and causing a mini sonic boom.

Even if the Tesla Coil operated at ultrasonic frequencies, a spark would always be finding new paths through the air, creating continuous crackling.

But you don't need a spark gap - if you want a high-voltage AC source, a Tesla Coil can provide it. You need to ensure that the coil and wires are well-insulated, and the load impedance is low enough so that the output voltage doesn't exceed the voltage rating of the insulation

You may have problems with radio-frequency interference - the Tesla Coil is effectively a poorly-shielded wideband radio transmitter, which will interfere with nearby electronics. Wideband transmitters like this were used on the Titanic, but were banned around the time of World War 1 as they waste valuable spectrum. It is best to operate the Tesla Coil inside a Faraday Cage.

[ScientificSorcerer (OP)]

Evan_au.  I hear what you say but If what you say is true then what is the point of a spark gap in the first place? To draw more current like a big resister in parallel? I was under the impression that the spark gap was completely vital for the tesla coil's construction but failed to understand why.

What dose the spark gap actually do?

[evan_au]

The Tesla Coil operates by the primary and secondary coils having the same resonant frequency, allowing efficient energy transfer despite the large air gap, and lack of an iron core to guide the magnetic field.

Sparks from the Secondary Coil (High Voltage)
The spark gap at the top of the tall secondary coil illustrates "man-made lightning", and is the spectacular (and spectacularly loud) demonstration that people come to see at museums.

It also plays another role in terms of providing a safe place for excess voltages to discharge if there is no load on the Tesla coil. Operated without a spark gap, the peak voltages can get very high; uncontrolled voltages can cause destructive arcing between turns of the secondary coil, or between the high-voltage secondary and low-voltage primary.

By connecting some high-voltage load (and ensuring there are no sharp points which will undergo corona discharge), you can drain the high voltage from the secondary without excess sparks and noise. However, the load resistance should not be so low that it suppresses oscillation of the secondary, and it needs to be a load that can work from very high AC voltages. Loads like vacuum tubes are usually designed to operate from DC supplies.

Sparks into the Primary Coil (Lower Voltage)
Early Tesla Coils used a spark gap to provide a voltage surge into the primary coil, triggering an oscillation (which then transfers to the secondary coil via shared magnetic fields). However, modern electronics are able to operate at quite high voltages, and so it is possible to drive the primary from an electronic circuit, without a spark gap on the primary.

See: http://en.wikipedia.org/wiki/Tesla_coil#Primary_switching

[woolyhead]

How do you make a quiet Tesla coil? when it's not overpowered, The only part of the device that makes a loud irritating noise is the spark gap. I hate the spark gap, is it possible to make a tesla coil without the spark gap? or at least one that makes little to no noise.

I was thinking of havig the device ultra high frequency so that the spark gap would make ultrasound would that work?

How about placing the coil and its output leads in a vacuum?

[wolfekeeper]

Look up 'solid state' Tesla coils- they don't have the spark gap.

Tesla coils can be very quiet provided you don't drive them hard enough to arc from the top hat.

The downside of solid state TCs is that they're not as robust; the semiconductors have to be protected from the high voltages of the secondary.

The spark gap was just used originally to produce an impulse to set off the oscillation of the primary; they didn't have any other easy way to do taht. They're still frquently used because they're very reliable, but for sure they're noisy.