Whether a sound is quoted as having a decibel value that is positive or negative, depends on how the reference level is set and on the way logarithms work. Quick definition: The decibel is the logarithm of a ratio referenced to a property In the case of sound, we normally take the threshold of human hearing as our reference point. The important part is what we choose as our reference. In fact, when it comes to sound, the decibel can refer to sound pressure levels, a voltage, or power. It is just a logarithmic ratio based on a reference level. The unit of that logarithmic scale is the decibel or dB.īut the decibel is not an absolute nor specifically a unit of loudness. You just need to understand that we take the logarithm of the ratio P/Pref where P is the level of our sound and Pref is our reference level. The exact decibel formula does not matter here. Specifically, the ratio of our sound level and a reference level. Instead, we use a non-linear logarithmic scale that represents the ratio of two sound pressure levels. So, using a linear scale in Pascals for loudness would be impractical. That is a difference of about 10 million. The quietest sound the human ear can perceive is about 20 µPa (0.000002 Pascals). To calculate the factor change for any decibel change, see the calculator on the sengpielaudio website. If you look at the specification sheet of a microphone it may include the maximum SPL of the microphone.Ī 10dB increase is approximately a factor of 2 increase in the perceived loudness. One measure that we can take of a sound’s loudness is its Sound Pressure Level or SPL, which is measured in Pascals. The decibel value is proportional to the logarithm of the ratio of the sound property and a reference property, or log(P/Pref). What is a decibel or dB in audio recording?Ī decibel is a unit used to express the level of a sound compared to a reference level, using a logarithmic scale. Why are sounds quoted in positive decibels but a DAW shows negative decibels.What is a decibel or dB in audio recording?.

Negative decibel scale