Both of these scales can range from -100dB to +24dB (approximately). There’s dBV, where the reference point is 0.775 Volts and there’s dBu where the reference point is 1.234 Volts. Like the two other scales I mentioned, they each have a reference point of 0dB, as well. In the analog audio world there are two other commonly used decibel scales. When someone says a human voice is at +75dB, what they are talking about is dBSPL (sound pressure level) where the reference point is also 0, which is at the bottom of the scale and represents absolute silence. Think of it as like maxing out your memory on your computer. Short answer: it’s setup that way because 0dbFS is the point when your system has run out of bits. Electromagnetic Vibrations, Waves, and Radiation. Difficulties with speech, comprehension becomes impossible without amplification. ![]() Speech has to be louder than normal, group conversations are difficult. where is the base-10 logarithm and is the threshold of hearing, The intensity is then described as being decibels, abbreviated dB. Difficulty understanding speech, higher volume levels are required for hearing TV and radio. Additionally, you can check out the mag2db function. I suggest you refer to the definition of the decibel first. Why is it setup this way? Well, that’s hard to answer without getting too technical. The decibel scale is a logarithmic scale that measures the intensity of sound. You can simply convert the results directly to the decibels scale and plot the transformed results using the polar function. So since your recorder is measured in dB Full Scale (the scale used for digital audio), and it’s reference point is 0, this is the highest possible point on this scale and incidentally the point at which your sound will become fully distorted. When analyzing a frequency response graph, it is important to pay attention to the decibel scale on the amplitude axis. For example, a sound at 80 dB is ten times louder than a sound at 70 dB. Remember that the decibel scale is nonlinear. The decibel scale is logarithmic, which means that each increase of 10 dB represents a tenfold increase in sound intensity. Decibels are not an measurement of a fixed value but rather they are a measurement of the change in value. A gunshot is the loudest common sound with a value of 140 decibels, a normal conversation has a value in the middle of the graph of 60 decibels, and the sound of breathing is the quietest with a value of 10 decibels. Yes, if the reference level used for decibel scale is above threshold of hearing. According to the chart, a 60 dB sound has an intensity that’s one thousand times that of the 30 dB sound (1,000,000 pW/m 2 compared to 1,000 pW/m 2). ![]() There are a variety of decibel scales, each with a different point of reference. Sound level is not the same thing as sound intensity. An example of log graph paper is shown on the right. I think the thing that isn’t making sense to you is that decibels are a measurement of a relative scale. There will never be the number zero displayed on a log scale they usually run from some power of 10 to some other power of ten.
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