4/23/2024 0 Comments Logarithmic decibel scaleLogarithmic scales are common, but often people are not shown how they work, why they are used, or when they are in use – hence this post. The decibel scale cannot be a ‘linear scale’ – we have already described that 120 dB must be much more than twice the sound level of 60 dB. In addition, 120 metres is twice as far as 60 m. So, when measuring length, the difference between 6 metres and 7 metres is the same number of metres (one) as the difference between 78 metres and 79 metres. Many scales are ‘linear’, so that equal shifts along the scale represent equal differences in the quantity concerned. The next question is ‘how do the numbers on the scale work?’ We will see this in the section ‘power quantities and field quantities’. In fact, even for the term ‘sound level’, there are two different ways of calculating decibels, depending on the meaning you give to it. For those who think those two terms are synonymous, we will provide a discussion of the problem with the term ‘loudness’ toward the end of the post. Quite often, you will see use of the cunning term ‘sound level’ (well, I did mention ‘signal levels’ for electronics…). We will base this post in the realm of acoustics, since it is probably in connection with sound that most people are familiar with this unit, but the principles can be applied to other applications such as signal levels in electronics, and amplification.Ī tempting answer to our question might be ‘loudness’. The first question is what decibels measure. There is more than one layer of demystification to take place, too, so stop at whichever point suits you best (hopefully, though, not this point right here!). This post aims here to demystify the decibel scale. And instinctively, you might realise this cannot possibly be the case. But unless you know how the scale works, you might be led to think that a rock concert is twice as loud as a conversation. We have probably all seen charts of the decibel scale like the one below.
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