In digital audio, in an audio editor system, the decibel levels are especially confusing. You just need to have a quantity or level that is lower than the reference level. And it is possible to have negative decibel measurements in all systems. So 0 dB in any system doesn't mean "nothing," it means that you're at the reference level, whatever that happens to be in that particular system. However, this can be misleading, since decibels are a ratio, not an absolute quantity. Many decibel systems appear to have levels from 0 dB and upwards. The Digital System for Decibels at Full Scale (dBFS) For example, the following are all somewhat related to sound:ĭBv or dBV - two types of decibels voltage, which use different reference levels In the embedded video (above), I cover the basics of a number of different decibel-based systems. If you were able to instantly turn the power output from a 100-watt light bulb into purely sound energy, it would almost certainly deafen you, and possible cause serious injuries to some parts of your body. The very loudest sound that we can hear before approaching the threshold of pain produces about one watt of power. The very dimmest light that we can perceive produces about one watt of power. It is also interesting that the power levels in light are much higher than in sounds. If you were to take the dimmest possible light that our eyes can see, and increase the power by only one thousand times, it would be at a level approaching the threshold of pain, causing retina damage. With light, the difference is only about three orders of magnitude. With sounds, we can hear a difference between power levels of twelve orders of magnitude, as mentioned above. Therefore, light travels at an almost constant speed, whereas sound propagates more quickly when the medium that it is passing through becomes more dense.Īnother interesting tidbit is that the difference in power levels between light and sound, as we perceive them, is not similar. However, light is a type of radio wave, and sound propagates through a medium in a wave-like pattern due to the oscillation of adjoining molecules. There are both similarities and differences in the ways that we perceive sound and light. For example, consider these:ġ0x power = +10 dB = "about twice as loud"ġ00x power= +20 dB = "about four times as loud"ġ000x power = +30dB = "about eight times as loud" Adding to the complexity is the fact that since the ear perceives different power levels on a different logarithmic scale than decibels (perhaps around Log 2, rather than Log 10), we get some very strange mathematical relationships. decibels) reflect exponential changes in power levels. Decibel systems are designed so that linear changes in the measurement units (ie. The range of difference in power levels between the quietest sound that a human can hear and the loudest sound before passing the threshold of hearing and reaching the threshold of pain is about one trillion times, or 10 to the twelfth power! That's a huge difference in scale. Power is the change in energy in a system over time, and is best measured on a logarithmic scale. The decibel is one tenth of a Bel, and is abbreviated dB.ĭecibels measure a change in power. They decided to come up with a type of measurement that they named the Bel, in recognition of Alexander Graham Bell's work with early telephones. The first need for a decibel system came about many years ago, when telephone companies were trying to measure losses and gains across power grids. Incidentally, decibels are also used to measure a large number of other logarithmic-based scales, such as power and voltage levels. The decibel system is a logarithmic system that is appropriate for exponentially variable sound levels. Your ears can hear everything from a light wind rustling through distant trees, to a loud jet engine, and they need to be able to process sounds appropriately. The decibel is the unit used to measure the intensity of a sound. This post is directly related to video #08 in my Audio Recording tutorial series, which is embedded below.Īlthough watching the video is the best way to learn about this topic, because of my illustrations on the whiteboard, I've also put a copy of the audio portion of that tutorial video on SoundCloud, for people who would like to download it to listen to in vehicles, while travelling, etc. Today, I have a post and video to delve more deeply into various decibel systems. I also have another post and video (numerically, the next in the series after this) that will talk about the Nyquist theorem, anti-aliasing, quantization noise, Fletcher-Munson curves, and dithering. That was part six of my Basic Audio Recording tutorial series on YouTube. Not long ago, I wrote a post and produced an associated video to teach people about sample sizes, sample frequency, binary, and how it all relates to sound. Decibel-based logarithmic measurement systems are confusing.
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