The psychological measure of the magnitude of a sound or sound object including its spectrum (frequency and intensity), harmonic content, duration and spatial properties.

Although volume increases directly with intensity and is colloquially identified with it, it will also be affected by reverberation and resonance, as well as by the presence of overtones or partials. An increase or decrease in any of these will affect the total perceived volume of a sound or sound environment. Multiple sources that are similar, such as in a choral ensemble, also enhance the volume of the resultant sound. See: Blend.

What might be called the 'constancy of volume' helps the auditory system resolve any ambiguity in loudness and distance, such as that between a distant loud sound and a softer nearby one. Acoustic sounds tend to retain their identity and sense of magnitude, regardless of distance or intensity level. In contrast, the parameters of electroacoustic sounds may be varied independently, such as when a fader changes the loudness of a sound without affecting its overall spectrum.

Compare: Amplitude, Dynamics, Dynamic Range, Mass, Power, Sone, Sonority, Sound Intensity, Sound Level, Sound Pressure, Timbre.

Two examples of shipbuilding, the first with hammering on a wooden hull in a small room, the second on a steel hull in a large space. Both examples are played with approximately the same sound intensity level but differ considerably in the volume of the sound.