We often say a signal is really loud if it reaches -1.0 dBFS, because 0 is the point of no return. What does this actually mean, in terms of sound? In a 24-bit system, any recording with a value higher than 0 dBFS will be registered as a neatly clipped square wave for the duration. As Bob Katz put it on his website, “ by definition, there’s nothing higher.” This is called “full scale,” and we call a decibel measurement in reference to full scale “dBFS." Digital systems differ in that there is a set ceiling, above which nothing can happen. In an analog system, a signal can get stronger than, and even pass the point of distortion. How does the decibel show up in our work? Making sure we don't hit our head on the digital ceiling (dBFS and the decibel in digital audio) It’s much more important to have higher resolution between -1 dB and -2 dB than it would be to have that resolution between -60 dB and -61 dB. This is extremely helpful from a practical standpoint, in something like a level fader. However, a linear scale sees these values spaced evenly, while a logarithmic scale has finer resolution as you move up the scale. Now, it’s important to clarify that linear and logarithmic scales both express the same minimum-to-maximum range and the same number of values. The log scale correlates better to how we perceive changes in SPL (sound pressure level) in the real world. This is the first reason the decibel is so useful to us: we can quickly calculate, automate, move, or jump through values that are exceedingly wide in range, in a manner that is easier to digest. Increase the sound to be 1000 times as powerful as it originally was, and that’d be 30 dB. 100 times as powerful would be a difference of 20 dB. If you were to increase a sound to be 10 times as loud, you’d measure an increase of 10 dB. This is very useful for the purposes of audio measurements, and here’s an example of how: Notice how the line isn’t straight-it bends severely at first, then evens out as the values get higher. You’ll note the word “Bel” has been shorn of exactly one “L.” This was probably done to keep the company name from being used without their consent. Thus, the “Bel” was born, named in honor of Alexander Graham Bell, the pioneer of the telephone. Things cleared up around 1928, when a conference called the CCIF ultimately decided upon standardizing the TU. There was no standardization-companies and countries had their own systems of measurement, making comparisons exceedingly complicated. In fact, “miles of standard cable”-MSC-was probably the first measurement, giving way to Bell Lab’s Transmission Unit-TU-in 1924.Ĭapitalism being capitalism, a number of measurements were put forth by competitive entities. They needed a measurement, one to define the amount of signal lost over, say, a mile of standard cable. To fix the situation, engineers needed a method of quantifying this loss in the first place. Engineers immediately saw that early phone calls lost signal strength over distance: signals grew fainter the further they had to travel. The decibel’s history is found in communications-particularly, the cables that carried phone calls. The Telegraph? Both the British Royal Navy and the Emperor of Russia were involved in the earliest, practicable designs. The radio? Same deal: it transmitted messages to soldiers without the need of telegraph lines. The compressor? Originally, it was used to ensure no radio orders to troops would be inaudible. Fun fact: you can generally assume that your favorite piece of audio technology was invented for the purposes of the military, communications, or communications for the military.
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