It does seem too good to be true, but that alone isn't a great reason to dismiss something. I have heard rough figures being quoted, since it's very simple to measure and demonstrate high efficiency.
The TV demonstration is in the original TED talk, which is probably a better ambassador than...
This makes a lot of sense. Thanks. I am visualising it as a DC magnetic bias that the permanent magnet applies, around which the solenoid current causes the field to oscillate. I guess the effect is the same as the string being magnetised so that the solenoid's magnetic polarity both attracts...
I think they have for transducers but not so much for exciters, since they would only be able to excite the string through a weak vibrational/sound coupling.
I have specifically tested an excited with and without a permanent magnet (and with permanent magnets of varying strength) and they strongly influence the force applied to the string. It doesn't seem to have much to do with the transduced signal feeding the amplifier, as the same behavior occurs...
I have been experimenting with solenoids used to excite steel guitar strings electromagnetically. These can be found in a variety of infinite "sustainer" products such as the ebow. They generally consist of a pickup, an amplifier and a solenoid which form a simple electromagnetic feedback loop...
What do you make of this? https://en.wikipedia.org/wiki/Resonant_inductive_coupling
There was a company Witricity that went viral a few years ago claiming efficiencies in the order of 98% over distances of like 2m, which seems extraordinarily high.
My skepticism is largely based on the...
I just thought it was odd that what seems to be the most ubiquitous pump has such relatively poor performance (thermodynamically). In comparison, other bits of rotodynamic machinery typically have much higher efficiencies.
Sorry. I should have made that more clear. It is a rocket engine which has a full flow turbine to drive a pump for propellants. I made a crude diagram of the two scenarios.
I have been playing around with pump curves a bit and have noticed that in general, the best operating point yields a pretty poor efficiency relative to the pump input power (75% max). From a second law perspective, there shouldn't be any losses. Where is all of this energy being lost? Is it in...
I still struggle with the interchangeability of pressure and temperature and how they affect the performance of various bits of turbomachinery. Microscopically they're very interconnected, in that the measure of pressure is the result of the confinement of the measure of temperature, however...
It's just a compressed air line which is modulated by a solenoid valve. There is no moving cone or enclosure. I want to create sound by directly modulating compressed air rather than pushing it using a cone.
Thanks for the links.
I found a fast solenoid valve lying around (~1ms rise time) so I thought it would be fun to hook up to a compressed air line and use to generate some really loud bass. I hooked it up to a function generator and air supply only to find that it was disappointingly quiet (well not quiet, but...
I don't understand why you are introducing temperature at all. I never discussed temperature. It seemed pretty obvious that the system is in thermal equilibrium. If I were to talk about a system in a room and never use words like "hot" or "cold" or "temperature", wouldn't you assume the system...
So in conclusion, a string cannot start to spontaneously oscillate at its natural frequency due to thermal motion of air molecules around it, given the system is at the same temperature as the air.
You seemed to disagree with this sentiment initially.