![]() She records the household washing machine from 1m distance. As long as the input gain is not changed (I sujested gaffer tape on the knob) then there is no further calibration to do. Read the OP, " My daughter is using Sonar for a science experiment to measure the relative volume of different sounds."Īll she needs do is set the input gain so that the loudest sound she's testing reads Full Scale (0dBFS) then all the other sounds will be x y z dB quieter than that. 1 Khz sine is a typical reference for normal hearing. What is the source of the sound? If you're trying use a meter to calibrate or compare you need a steady state sine wave. Use a table of known levels from Wiki to convert your dBFS readings to dBspl if you wish as I showed you before. ![]() If you have two or three or more recorders, perform the same calibration on them with the same sound source at the same distance and all your equipment will give you the same readings. You simply choose the loudest sound you want to record and adjust the input gain untill the meters read Full Scale. ![]() It is a good choice to use because it is very easy to calibrate. If you buy an expensive (or cheap) sound level meter then you're paying for the calibration of its mic amp to be accurate.ĭBFS (Full Scale) is simply a level that makes your meters hit Full Scale. The recording level will be determind by the gain of your input amp. The perceived volume on playback would depend on the size of amplifier you play it through. The most common audio reference points are defined like this:ĠdBFS = Full Scale digital, the largest number that can be represented digitallyĠdB SPL = 20 micropascals (Sound Pressure Level)ĠdBV = 1Volts RMS, so 0dBV means X=1V RMS, +X dBV means greater than 1V RMS, and -X dBV means less than 1V RMS.ĭoes this mean "Jack Hammer -20dB" in the example above could be different perceived volume if recorded on or played back on different equipment? Does this scale (dBFS) only refer to recorded sound? (ie. If you are comparing 2 values, you just use "dB" (X is +20dB compared to Y). When you specify a reference standard (like dBFS, dB SPL, dBu, dBV), you are comparing a single value to a predefined reference point ("X is -20dBFS" means X is -20dB compared to the predefined reference of 0dB = full scale digital). A ratio of 1:1 = 0dB ratios greater than 1 = +X dB ratios less than 1 = -X dB. I will add this: dB's are a logarithmic way of expressing a ratio. In that case, you're talking about the change in an already assumed dB scale of some sort. "I turned it down 6 dB" or "that pre gives 60 dB of gain". You have to know the reference level for dB to mean anything.ĭB by itself is only used when talking about a change in level. With the K-20 Metering system you set your levels so that -20 dBFS RMS equals 83 dB SPL. Since analog usually has 'headroom' you calibrate so that -20 dBFS equals 0 dBu on your analog meter-depending on the headroom of course. When you interface digital gear with analog, you want to calibrate levels. That's why you sometimes get positive and negative values for dB-it all depends on the reference level. So when you're at the clipping point you get 0 dBFS and you go down from there. In the case of dBFS, the reference is 'full scale' which, in digital, is the clipping point of the converter. 0002 microbar you get 0 dB SPL, and it usually goes up from there. In the case of dB SPL, when the measurement equals. And when the measurement equals that standardized level you get 0 dB-in-whatever-scale. dB scales are always in reference to some standardized level. "dB" all by itself doesn't really have a meaning. ex: Jet plane 100mĭB (used in audio measurement) = How much louder a sound is when compaired to the threshold of human hearing. EDIT : or note the distance to the sound in the results. ![]() Remember that for any of your results to be valid the sounds must be recorded with the same mic at the same distance to the sounds. Now leave the mic gain alone, (put gaffer tape over it) and all your recordings/test will be relative to your loudest example. Just start with the loudest sound you're expecting to test and set the sound card input gain, (or portable recorder mic gain) to show Full Scale. ![]() The decibel will tell you how much louder or quieter one sound is when compaired to another, it will NOT tell you the precise volume of a sound (although you could work that out)įor the purpose of the school work, dBFS would give perfectly usefull results, is readily available in Sonar and can be calibrated easily. The important part to note (to impress teacher) is that the decibel unit is a comparative measure, NOT an absolute. DBFS = how much quieter a sound is compaired to a sound that would make your equipment read full scale.ĭB (used in audio measurement) = How much louder a sound is when compaired to the threshold of human hearing. ![]()
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