Symbol	Description	Unit
$p(r,t)$	Time-domain sound pressure	Pa
$P(r,\omega )$	Frequency-domain sound pressure	Pa·s
$c$	Speed of sound (343 m/s)	m/s
$k$	Wavenumber ($=\omega /c$)	rad/m
$\omega$	Angular frequency	rad/s
$f$	Acoustic frequency	Hz
$G(r,r_0,\omega )$	Free-space Green’s function	m−1
$G_{\mathrm{t}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}}$	Total Green’s function with ground reflection	m−1
$\alpha$	Ground-reflection coefficient	—
$r_0$	True source position $(x_0,y_0,z_0)$	m
$r_{0^{\prime }}$	Image-source position $(x_0,y_0,-z_0)$	m
$r$	Observation point	m
$p_m$	Position of $m$-th microphone	m
$M$	Number of microphones	—
$d$	Microphone spacing	m
$D$	Array aperture	m
$\lambda$	Wavelength	m
$X_m\left(\omega \right)$	Frequency-domain signal at $m$-th microphone	Pa·s
$N_m\left(\omega \right)$	Noise at $m$-th microphone	Pa·s
$w_m$	Channel weight	—
${\tau }_m\left(p\right)$	Propagation delay from source candidate $p$ to $m$-th microphone	s
$P\left(p\right)$	Spatial spectrum at candidate position $p$	—
$p_s$	Estimated source position	m
$f_s$	Sampling rate	Hz
$N$	Frame length	samples
$\mathsf{\Delta }t$	Frame interval	s
${\sigma }_f$	Decay rate of frequency weighting function	Hz