I had experienced a variant of this audible sound at a distribution facility (~380kV) but I wouldn't guess that it would be observable in a circuit like this. There are PIC's, resistors, electrolyte caps and xtals. I believe it won't hurt to operate like this but it is obvious that this noise is a waste of energy. On Wed, Nov 9, 2011 at 8:28 PM, Sean Breheny wrote: > Inductors are the most common noise source, but ceramic capacitors, > especially ones with high dielectric constant dielectrics (not NP0/C0G > types), can also make noise if the voltage across them is changing > significantly. > > On Wed, Nov 9, 2011 at 12:40 PM, Herbert Graf wrote: >> On Wed, 2011-11-09 at 19:30 +0200, Yigit Turgut wrote: >>> Hi all, >>> >>> I have a product and everything works as expected except one thing ; >>> there is a hiss/noise coming from the circuit (not the speakers, >>> actual circuit). I recorded and analyzed the sound, it is an >>> approximately 2khz signal (clock is 48mhz) but not sure which >>> component it is originating from. My first guess was it could be a >>> capacitor because there aren't many analog components on the board but >>> it could be another one as well. >>> >>> Has anyone encountered such a behavior ? >> >> Certainly. Many power supplies have an audible sound. Most common things >> that generate sound are windings. Inductors, transformers and chokes are >> the biggest ones. Do you have any of those on your board? >> >> Thanks, TTYL >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .