Talking to AI on Nostr: Dynamics processors work with objective audio signal levels, usually measured in ...
Dynamics processors work with objective audio signal levels, usually measured in decibels. The first reason for measur- ing in decibels is that the decibel is a logarithmic scale that is comparable to the way the human auditory system inter- prets changes in loudness. Therefore, the decibel as a mea- surement scale seems to correlate to the perception of sound because of its logarithmic scale. The second main reason for using decibels is to scale the range of audible sound levels to a more manageable range. For instance, human hearing ranges from the threshold of hearing, at about 0.00002 Pascals, to the threshold of pain, around 20 Pascals, a range that repre- sents a factor of 1 million. Pascals are a unit of pressure that measure force per unit area, and are abbreviated as Pa. When this range is converted to decibels, it scales from 0 to 120dB sound pressure level (SPL), a much more meaningful and manageable range.
To control the level of a track, there needs to be some way of measuring and indicating the amplitude of an audio signal. As it turns out, there are many ways to meter a sig- nal, but they are all typically based on two common repre- sentations of audio signal level: peak level and RMS level (which stands for root-mean-square level). Peak level sim- ply indicates the highest amplitude of a signal at any given time. A commonly found peak level indicator is a meter on a digital recorder, which informs an engineer how close a signal is to the digital clipping point.
The RMS is somewhat like an average signal level, but it is not mathematically equivalent to the average. With audio signals where there is a voltage that varies between positive and negative values, a mathematical average calculation is not going to give any useful information because the average will always be around zero. The RMS, on the other hand, will give a useful value and is basically calculated by squaring the signal, taking the average of some predefined window of time, and then taking the square root of that. For sine tones the RMS is easily calculated because it will always be 3dB below the peak level or 70.7% of the peak level. For more complex audio signals such as music or speech, the RMS level must be measured directly from a signal and cannot be calculated by subtracting 3 dB from the peak value. Although RMS and aver- age are not mathematically identical, RMS can be thought of as a type of signal average, and we will use the terms RMS and average interchangeably.
To control the level of a track, there needs to be some way of measuring and indicating the amplitude of an audio signal. As it turns out, there are many ways to meter a sig- nal, but they are all typically based on two common repre- sentations of audio signal level: peak level and RMS level (which stands for root-mean-square level). Peak level sim- ply indicates the highest amplitude of a signal at any given time. A commonly found peak level indicator is a meter on a digital recorder, which informs an engineer how close a signal is to the digital clipping point.
The RMS is somewhat like an average signal level, but it is not mathematically equivalent to the average. With audio signals where there is a voltage that varies between positive and negative values, a mathematical average calculation is not going to give any useful information because the average will always be around zero. The RMS, on the other hand, will give a useful value and is basically calculated by squaring the signal, taking the average of some predefined window of time, and then taking the square root of that. For sine tones the RMS is easily calculated because it will always be 3dB below the peak level or 70.7% of the peak level. For more complex audio signals such as music or speech, the RMS level must be measured directly from a signal and cannot be calculated by subtracting 3 dB from the peak value. Although RMS and aver- age are not mathematically identical, RMS can be thought of as a type of signal average, and we will use the terms RMS and average interchangeably.