I wish to calculate room noise level using the computer's microphone. I record noise being an audio file, but how do i calculate the noise dB level?
I'm not sure how to begin!
You cannot easily measure absolute dB SPL, as your microphone and analogue hardware aren't adjusted. You might have the ability to do approximately calibration for the hardware setup but you should continue doing this for each different microphone and hardware setup that you're planning to aid.
Should you do possess some type of SPL reference source which you can use then it will get simpler:
- make use of your reference source to develop a tone in a known dB SPL - measure this
- appraise the ambient noise
- calculate noise level =
20 * log10 (V_noise / V_ref) + dB_ref
Obviously this assumes the frequency response of the microphone and audio hardware is fairly flat which you simply desire a flat (unweighted) noise figure. If you prefer a weighted (e.g. A-weight) noise figure then you will need to do more processing.
You need to do need reference hardware (i.e., a reference mic) to calculate noise level (dB SPL, or seem pressure level). Radio Shack sells very couple of stuff that count anything, but one of these is really a $50 dB SPL meter. If you are doing scientific information, I would not utilize it. But when the aim is to buy an over-all concept of a weighted measurement (dBA or dBC) from the seem pressure inside a given atmosphere, then it may be helpful. Like a seem engineer, I personally use mine constantly to determine just how much seem volume I am producing as i mix. It's often accurate to within 2 dB.
That's my answer. The relaxation is FYI stuff.
Jorg is factual that dB SPL is really a relative measurement. All decibel dimensions are. But you've implied a reference of dB SPL, or 20 micropascals, scientifically decided to function as the most silent seem an individual ear can identify (though, naturally, what an individual can really hear is tough to determine). This, based on Wikipedia, is one of the seem of the flying bug from about 10 ft away (http://en.wikipedia.org/wiki/Decibel).
By presuming you do not understand sound levels, I believe Jorg is simply attempting to out-geek you. He clearly did not provide you with a practical answer. :-)
Unweighted dimensions (dB, rather than dBA or dBC) are hardly ever used, since most seem pressure isn't detected through the human ear. Inside a given office atmosphere, there's usually 80-100 dB SPL (seem pressure level). To provide you with a concept of just how much is not heard, within the U.S., work rules limit noise contact with 80 dBA for any given 8-hour work change (80 dBA is one of the background noise degree of your average downtown street - difficult, although not impossible to speak over). 85 dBA is oppressive, and also at 90, many people are looking to get away. Therefore the distinction between 80 dB and 80 dBA is very significant -- 80 dBA is tough to speak over, and 80 dB is very peaceful. :-)
What exactly is 'A' weighting? 'A' weighting makes up for the truth that we do not see lower frequency sounds in addition to high frequency sounds (we hear 20 Hz to twenty,000 Hz). There is a lot of low-finish rumble our ears/brains virtually ignore. Additionally, we are more responsive to a particular midrange (1000 Hz to 4000 Hz). Most agree this frequency range consists of the sounds of consonants of speech (vowels happen in a reduced frequency). Imagine speaking with only vowels. You cannot understand anything. Thus, ale an individual to have the ability to communicate (traditionally) rests within the 1kHz-5kHz bump in hearing sensitivity. Oddly enough, for this reason most telephone only transmit 300 Hz to 3000 Hz. It had been determined this was the minimal response required to comprehend the voice alternatively finish.
However I think that's a lot more than you desired to understand. Hope it will help. :-)
You cannot. dB is really a relative unit, IOW it's a unit for evaluating two dimensions against one another. You are able to only state that measurement A is x dB even louder than measurement B, however in your situation you simply have one measurement. Therefore, it really is not easy to calculate the dB level.