Decibel is defined as a unit that indicates the presence of a tone relative to a reference pressure: dB 20 log (p/po) where p is the pressure of the tone and po is the reference pressure.
In the field of psychology, the term "decibel" (dB) might be used to describe the intensity or volume of a sound. The decibel scale is a logarithmic scale that is used to measure the intensity of a sound based on how much it differs from a reference level. The reference level for decibels is typically set at the threshold of hearing, which is the lowest level at which a sound can be heard.
For example, a sound that is 10 dB louder than the threshold of hearing would be perceived as being twice as loud as a sound that is at the threshold of hearing. Similarly, a sound that is 20 dB louder than the threshold of hearing would be perceived as being four times as loud as a sound that is at the threshold of hearing.
In psychology, the decibel scale might be used to measure the intensity or volume of sounds in a variety of different contexts, such as in research on hearing or auditory processing, or in studies of the effects of noise on cognition or behavior.