Sections
Key Equations

# Key Equations

 speed of sound $v=fλv=fλ$
 intensity $I=PAI=PA$ sound intensity $I=(Δp)22ρvwI=(Δp)22ρvw$ sound intensity level
 Doppler effect observed frequency (moving source) $fobs=fs(vwvw±vs)fobs=fs(vwvw±vs)$ Doppler effect observed frequency (moving observer) $fobs=fs(vw±vobsvw)fobs=fs(vw±vobsvw)$
 beat frequency $fB=|f1−f2|fB=|f1−f2|$ resonant frequencies of a closed-pipe resonator resonant frequencies of an open-pipe resonator