Greetings to all,
I was thinking about building low-cost analog sound level meter, however, i am not sure how to get the non electrical value of sound pressure and transform it in electrical value. I planned to display the level with (cascaded) LM3915s', but was wandering about ideas of how to obtain sound pressure level in the first place.
Thanks in advance!
-- Kupio sam pistolj od svercera na crno, Na tebe cu rado da potrosim zrno...
Google is your friend.
You can get audio spectrum analyzer programs that run on your PDA to do that function. Plug a microphone into your sound card and download a free audio spectrum analyzer program.
You don't say what test equipment you have, but using the sound card and replacing one function in the chain at a time will get you there in steps.
Your most difficult problem is the LARGE dynamic range that the system has to handle. You'll end up with a bunch of range switches that make the project 10X more complex...not difficult, just complex. mike
-- Wanted, Serial cable for Dell Axim X5 PDA. Return address is VALID but some sites block emails with links. Delete this sig when replying. FS 500MHz Tek DSOscilloscope TDS540 Make Offer Bunch of stuff For Sale and Wanted at the link below. MAKE THE OBVIOUS CHANGES TO THE LINK http://www.geocities.com/SiliconValley/Monitor/4710/
--Howzabout using a speaker as the input device?
-- "Steamboat Ed" Haas : Doodle doodle dee Hacking the Trailing Edge! : Wubba wubba wubba...
This is a non-trivial problem. You need a calibrated microphone to do this. Laboratory-grade "condenser" microphones which have stable performance are very expensive ($1000) and require 200 VDC supplies and special preamps. Instead, you can get a cheap microphone that has a calibration curve. Panasonic electret capsules come to mind, available from Digi-Key last time I looked. You will have to accept that the calibration will be crude at best, and will not last indefinitely. (Electrets lose sensitivity over time.)
Be sure to get an "omnidirectional" model, since the "unidirectional" units generally have much poorer frequency response.
The calibration information will consist of a frequency response curve (which for an omni electret will be pretty flat) plus a sensitivity value. A typical listing is "-62 dB +/-3 dB (0 dB =
1V/ubar, at 1000 Hz)" For more information on how to use this to go from volts to SPL, see "Some formulas for working with sound" atHope this helps!
Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.