A mixer routes all channels to the 'master bus' output channel, which has its own volume control. A mixer-channel cannot have a fixed frame of reference because it gets mixed. Any dB scale requires a defined reference point, which doesn't exist in this context. I can see now that using a simple low-to-high dB meter wouldn't make any sense. Now that I've done my research, the dB markings on a mixing desk look far more logical. 10k 100k 10k 100k 0 +10 +20 -10 -20 -30 -40 -50 Gain (dBFS) The graph on the left shows an 'A' scale frequency response curve, while the graph on the right shows one that more closely matches the response of an average human ear. These are much more complex than the 'A' scale, with peaks and troughs at different frequencies. A less-simplistic approximation of what our ears hear would be a 'hearing response curve'.It's simplistic, but 'close-enough' to have become a standard. This is a 'band-pass' filter, which is less sensitive to very high and very low frequencies. The most common filter is the 'A scale' (dBA).This more accurately describes the idea of 'volume' as humans understand it. If you want to reference 'loudness' using decibels, then you need to apply a filter of some kind.

So be careful, you could do lasting damage without realizing. Levels of >120 dBSPL will damage our ears, but our pain threshold is somewhere around 150 dBSPL.The reference point for dBSPL is 20μPa (micropascals) - roughly the limit of sensitivity of the human ear. To use a decibel this way, we need a fixed point of reference. Just like 20 metres is the same length wherever you go, 20 dBSPL always represents the same level of sound pressure. dBSPL represent an absolute value of sound pressure.In this context, the unit we're using is dBSPL (decibels relative to sound pressure level). When decibels are used to express 'loudness', (for instance, by journalists) they are used with a fixed point of reference.Humans don't hear all frequencies equally, so 'loudness' is a subjective concept. Decibels are a technical measure of intensity and/or pressure.This works because they are relative and logarithmic. They are a good unit for expressing very small and very large differences, and can do both on the same scale.Decibels are measured using a logarithmic scale 2.That means it expresses a ratio, and not an explicit value.

I did some research, and it turns out the decibel is actually pretty interesting. So after years of pretty much taking the decibel for granted, I finally had enough. I would often catch myself thinking 'I know they are getting it wrong, but I don't know why'. As such, I'd feel uneasy when I overheard a lay-person talking about volume. The mixer section of Logic X (a typical DAW - Digital Audio Workstation)įor a long time I've been at least tangentially connected to the world of 'pro' audio. The desk shows the loudest value as zero, all the way down to silence at '-96' (or sometimes even '∞'). But when I look at the volume meter on a mixing desk, things are different. 'It's louder than a jet engine at 50 paces, man'. Sound engineers do it too, when boasting about the power of their speaker-setup. Journalists do this when describing how loud a band is 1.

Sometimes people use decibels as an absolute value where '0' is silence and anything over '120' is very loud.

Decibels scale usefulness