Pressure is scalar while velocity gives a sound wave its direction

Evidence

Air pressure acts in all directions at the same time and therefore for sound it can be considered to be a scalar quantity without direction; we can therefore talk about pressure at a point and not as a force acting in a partic­ ular direction. Velocity on the other hand must have direction; things move from one position to another. It is the velocity component which gives a sound wave its direction. — David Howard, Jamie Angus, coustics and Psychoacoustics, 146

Air pressure acts in all directions at the same time, and therefore for sound it can be considered to be a scalar quantity without direction; we can therefore talk about pressure at a point and not as a force acting in a particular direction. Velocity, on the other hand, must have direction; things move from one position to another. It is the velocity component that gives a sound wave its direction. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 164

Categorization

• DEFINE: Clarifies the scalar/vector distinction between pressure and particle velocity — central to understanding why measuring acoustic fields needs both quantities.
• XREF: Connects to the reader’s interest in listening and the physics beneath perceptual fields like psychoacoustics. — connects to: All acoustic impedances are ratios of force to velocity; Sound waves have an inherent velocity component tied to molecular displacement.; Medium density and elasticity shape the pressure-velocity amplitude relation — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 165 (+3 more)
• corroborated: 6 independent passages support this claim — David Howard, Jamie Angus, coustics and Psychoacoustics, 146; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 164

Broader Connections

• Sound waves have an inherent velocity component tied to molecular displacement. #expands (0.85)
• Sound waves are longitudinal waves of alternating compression and rarefaction #expands (0.80)
• Medium density and elasticity shape the pressure-velocity amplitude relation #expands (0.75) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 165