ABSTRACT
Amplitude (Loudness) Each peak high and low pressure point along the graph's y-axis has a specific height or amplitude, which is a measure of the loudness of a sound (see Figure 15-3). The higher the amplitude peak, the greater is the displacement pressure of the sound wave and the louder the sound. Loudness is measured in decibels (dB). Decibels increase or decrease according to a logarithmic progression. I won't go into the complexities of logarithms; it's sufficient to simply understand that it takes an increase of three decibels (3 dB) to double the loudness and a decrease of three decibels to halve loudness.
