Decabel Meter

[arj256]

I was thinking of making a decabel meter and was considering how to make it.
I would like it to be able to measure up to 50 decabels which would be shown on a led.
I would have 5 leds, each one equalling 10 decabels.
How would i make this work?
Do you have any ideas on the circuit as i am not sure which/how to construct it.
Thanks.

 

[mechie]

dB measurement

10dB steps are a bit big - the basic unit, the Bel, is rarely used for that reason.
However ...
Assuming you are measuring sound levels, a microphone, amplifier and voltmeter is about what you need to get going. The voltmeter could easily be an LED bargraph
The subject of sound level measurement can be a bit heavy on theory if you worry about the weighting filters that can be used in professional gear -- dBA (common - matches your hearing in normal conditions), dBB, dBC (used for extreme noises - your hearing works differently at a disco!).

Decibels can also be used for comparing voltages, currents, RF aerial efficiency, all sorts of things as it is at its simplest a lograthmic comparison of a known and measured quantity.

 

[bogdanfirst]

my idea is to use a microphone, an amp and a VUmeter...maybe its harder to adjust it, but mught work

 

[herbymcduff]

you know how fun it is to work on things. But then you get frustrated that you can't figure it out. I would probably go and buy one. Or maybe find out a company that makes one, and ask for a schematic. Bogdanfirst idea sounds sound. Maybe you should try that to.

 

[kevinkirkp]

Well, I have actually seen some schematics on the web that claim to measure sound in this manner. If still interested, I can try to find the link in my Favorites. I can remember the curcuit using LEDs as the meter. I am not sure what the resolution was for this schematic. One problem you will encounter is the calibration of the circuit. The type of microphone (condenser/eletrolet) will play a big part in the calibration, meaning that voltage coming from these will vary depending on type of microphone. The sound meters on the maket typically do not measure in the range you specified. The best I have seen out there was from 30 on up to 130dB. Most are from 50 up. Accuracy on these manufactured devices are -+ 2dB which is pretty good. Ones that measure lower sound pressures are rather expensive.

 

[bogdanfirst]

also if you use an electret mic, you should know that it doesnt have such a liniar characteristic.
anyway what do you need it for?