![negative decibel scale negative decibel scale](https://www.commodious.co.uk/xiveillancetraining-env/1961/noise-chart2-sml.png)
Sound pressure is the difference between the pressure from a sound wave and the ambient pressure of. Simply put, decibels are a measure of the sound pressure level. We convert that into the more popular decibel scale or dB scale. If I were inventing the audiogram I would have labled it as negative dB going down, but it’s the same thing, just looking at it from the opposite direction. Sound pressure level, or SPL, is a measurement of sound pressure that uses Pascals (Pa) as its unit of measurement. Apparently their scale shows dB of loss rather than negative dB for “negative gain”.
![negative decibel scale negative decibel scale](https://thumbs.dreamstime.com/b/decibel-scale-sound-level-102089644.jpg)
Notably, and IMO strangely, the audiograms we make for our hearing profiles show positive dB for more hearing loss. On a boost graph like in the software you pictured, they may be showing the gain of the amplifier on the curves. But the convention on volume controls is to put 0dB at the maximum and have all the numbers be in negative dB. Where the amplification was neutral the label would be 0dB in that case, and when it became lower level than the input it would have negative dB numbers on the label. A decibel is defined as: dB 20log10(Vout Vin) (1) (1) d B 20 log 10. Your volume control could be labeled 6dB at the maximum and go down from there. Because an ideal analog filter would not attenuate the signal but only the noise, the decibel scale is used to express the degree of electrical attenuation (or gain) attributable to an electronic device, such as a RC filter.
![negative decibel scale negative decibel scale](https://www.apogeeweb.net/upload/image/20201104/2020110411503558.jpg)
It makes things easier if a logarithmic scale is used this is what the decibel scale is. The ratio of intensities between silence and ‘ow that hurts my ears’ is about 1:100 million million. Say your amplifier doubled the sound level (voltage level). The human ear is capable of hearing very quiet (low intensity) sounds and extremely loud (high intensity) sounds. On a logarithmic scale, values change quite differently. As you can see, the value grows evenly as it moves across the graph. A graph displaying a linear function: y x. To help us understand the difference, let’s take a look at linear growth on a graph. Of course, you can express the gain of your amplifier as so many dB and label the top end of the volume control at that number of dB. The decibel employs a logarithmic scale, not a linear one. The labels on the potentiometers start at 0dB at maximum and go down from there. Volume controls in analog electronics are potentiometers (variable resistors) which divide the input voltage level, so you can only go down from maximum. Whatever that gain is, it’s called 0dB on the volume control. Typically, amplifier systems have a certain gain going straight through without any volume control on the input. The gain toggles in the middle probably hit zero as their top end and go negative from there as you toggle them down. In the output level chart, the smaller (positive) dB numbers are at the bottom and the larger (positive) dB numbers are a the top. A larger minus dB number (in an amplifier) is a lower sound level.