![]() From these contours, compiled via extensive laboratory testing, we can deduce that we are most sensitive to frequencies between roughly 1kHz and 6kHz, and must adjust levels upward in lower and higher frequencies to attain the same perceived loudness. The Fletcher Munson Equal-Loudness contours are a graphical representation of our sensitivity to various parts of the frequency spectrum.Įach line represents an equal perceived loudness level at various frequencies. This perceived level is subject to environmental issues like temperature and is also frequency dependent. That is the quietest sound a human being with undamaged hearing can detect given a test tone of 1000Hz. But saying that The Who concert in 1976 broke the world record for loudness at 126dBSPL at a distance of 105 feet from the stage is meaningless, unless you compare that to 0dBSPL at the same distance, which is the Threshold of Human Hearing. A Pascal (named after Blaise Pascal) is a unit of force equivalent to one Newton (named after Sir Isaac Newton) per square meter.Ī Pascal is an absolute unit that can be measured. Otherwise, it’s just trial and error.ĭBSPL refers to Sound Pressure Level and indicates a value relative to the Threshold of Human Hearing which is commonly believed to be 20 Micropascals (.000020 Pascals or 20 millionths of a Pascal). That is, your knowledge of what sonic effects will be created by a particular slider or knob before you make the adjustment. Having a good understanding of these ideas will speed up your mixing process substantially by fine-tuning your isomorphic mapping abilities. A 6dB change is perceived as a significant change in level and 10dB to 12dB can be heard as a doubling or halving of loudness. Most people begin to hear a slight change in level at plus or minus 2dB to 3dB. 0dBFS is the absolute peak in a digital system after which samples will be clipped. The levels commonly found on a track in a DAW are dBFS or Full Scale. But if we compare it to some level we’ll call 0dBSPL, we can say that it is roughly half as loud. For example, -12dBSPL by itself is meaningless. So decibels express amplitude or loudness levels as a value relative to some reference value or beginning value. A linear scale would be far less intuitive in terms of frequency or amplitude. This human perception is best visualized using a logarithmic scale so the physical distance on the graph between various octaves (e.g. In fact, we hear the distance between 200Hz and 400Hz as the same, which is the interval of an octave or a doubling of frequency or a 2:1 ratio. Although the numerical distance between 100Hz and 200Hz is the same as that between 200Hz and 300Hz, we do not hear that distance as the same. Find more explanation of logarithms here. This is a logarithmic scale based on powers of 10. For instance, from 100Hz to 200Hz is spaced farther apart than is 200Hz to 300Hz. Note that the vertical lines represent frequency values that do not look equally spaced. Consider the layout of a parametric EQ seen below. This might best be understood in terms of our perception of frequency. ![]() Linear scales represent a change in values as a difference, whereas logarithmic scales represent changes as a ratio. Human hearing is best measured and represented with a logarithmic scale as opposed to a linear scale. ![]() In other words, decibels are relative as opposed to absolute units. The Decibel is a logarithmic unit that expresses value in relation to another value. Most amplitude measurements use decibels in one form or another. Key to this is understanding the decibel (dB). In working with sound it is essential to have a firm grasp of amplitude and loudness and the various methods of measurement.
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