Misc. ?'s about air flow, electricity, and audio

[isochar]

Does the airflow of the outside fan in this picture increase since there is a 2nd fan blowing into the power supply? (The guy states that the CFM will be the same as just 1 fan, just confirming it)

http://w3.one.net/~robotech/quiet_psu.htm

If it doesn't change CFM, then why would the temperatures stay the same if there is only 24CFM going through the power supply rather than the default 37CFM?

Would this be an adequate way of discharging the capacitors in my power supply?

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F010%5F001%5F008%5F000&product%5Fid=271%2D135&MSCSProfile=745D84CBF04D14A48AA6FF9C89D722C0BA68C1B04FE384678A5285FCD6E056B17AF21627FDABE316B90B3C038D68EBD6B7F9F3BD1712EAA9951ACB2590A05C6517EFE46941FEFDD1985D4EFD6321F5E70B4DE9B6C1D45512A2E2690A6961FCE4A11C7836B7679A4B3A1AC949C2BC9E98EAED42030051E4D97440BE4B9046D4D945034E361F623540

Anyone know of any (hopefully inexpensive) dB meters that can measure from 0 dB and up?

[Greebe]

Does the airflow of the outside fan in this picture increase since there is a 2nd fan blowing into the power supply? (The guy states that the CFM will be the same as just 1 fan, just confirming it)

No. Unless a fan is run in a unblocked free space it will not move the same amount of air as it's rated for. So from the get go it's already less than they claim. Running two fans in parallel does two things that improve cooling. One is that when placing two in parallel effectly makes the PSU box an isobaric chamber which will improve airflow... analogous to a 4 wheel drive climbing a hill. Second thing it does is stir the air within the PSU box so more heat is disperced effectively.

If it doesn't change CFM, then why would the temperatures stay the same if there is only 24CFM going through the power supply rather than the default 37CFM?

It does cool it more effectively for the above reason.

Would this be an adequate way of discharging the capacitors in my power supply?

Yes, but insulate it entirely first and don't use on HV ever! (ie >600v)

Anyone know of any (hopefully inexpensive) dB meters that can measure from 0 dB and up?

You can't buy an inexpensive calibrated SPL meter per se. Even then 0dB reference is next to impossible to create or it's it's responce isn't flat.
But do know exactly what you are driving at and here are a couple that can be picked up for cheap...

Analog SPL Meter
Digital SPL meter

To see what is really neccessary you honestly need a 1/3 octave Spectrum Anaylizer. Whether it be a standalone unit or a done from a PC ie a good soundcard/calibrated microphone and an app like CoolEdit or the like can do this with much better accuracy (do get a calibrated white noise source to ensure integrity of calibration)

[isochar]

Thanks for the responses, Greebe. I've had the analog Radio Shack meter for some time, but its lowest setting is 60dB - not low enough to measure how quiet my case fans actually are.

As for the airflow, is there any rule of thumb as to what 2 low speed fans in the above configuration would be effectively be able to replace? (ie. If the original 80mm fan is moving 44CFM instead of 37CFM)

Lastly, out of curiousity rather from a purpose, how would one go about discharging HV capacitors?

[Greebe]

Thanks for the responses, Greebe. I've had the analog Radio Shack meter for some time, but its lowest setting is 60dB - not low enough to measure how quiet my case fans actually are.

There lies your problem with measuring low acoustical noise. Your average room is ~>45dBA even in the quietness of the country it can easily be 35dBA. Without an anechoic chamber you can't measure them accurately.

As for the airflow, is there any rule of thumb as to what 2 low speed fans in the above configuration would be effectively be able to replace? (ie. If the original 80mm fan is moving 44CFM instead of 37CFM)

Nope. The reason is because it's all based on pressure, how much air restriction and or incoming airflow/ exhaust blockage.

But then again more is always better...

Lastly, out of curiousity rather from a purpose, how would one go about discharging HV capacitors?

Using a HV resistor of higher ~< 1kOhm value attached to a highly insulated probe. Additionally the grounding lead is normally insulated with teflon and can withstand HV requirements of what ever it is going to be attached to ie be discharged (typically >20kV). I might add that unless you really know what you are doing (unlike asking this question in the first place) it's best to keep your hands out. It's dangerous enough for someone to fiddle around near 120vac let alone high tension. Once you exceed 600v life becomes quite threatened and especially true when you exceed ~6kV. Normal materials will break down and conduct. Needless to say if you don't have the training/experience working with high tension, DON'T! I can tell you personally you would never want to have that experience.

[isochar]

Thanks again.

[isochar]

Just found these:

http://www.extech.com/Products/Instruments/sound/sound.html

They have ~$80 models that can handle 40dB and up, and ~$200-400 models that can handle 30dB and up. You wouldn't happen to know of other manufacturers that offer these performance levels at more affordable levels?

[Greebe]

You wouldn't happen to know of other manufacturers that offer these performance levels at more affordable levels?

Nope, that's as cheap as they come

To only get part way to what your wanting todo would reguire a min of ~$1,000,000 investment if not considerably more. Not to mention remotely isolated land inwhich to build the anechoic chamber on.

BTW you can't measure to 0dB